Merge branch 'master' of ssh://git.gag.com/scm/git/fw/altos

36 files changed, 8086 insertions, 0 deletions

diff --git a/src/scheme/.gitignore b/src/scheme/.gitignore
new file mode 100644
index 00000000..ee72cb9d
--- /dev/null
+++ b/src/scheme/.gitignore
@@ -0,0 +1,2 @@
+ao_scheme_const.h
+ao_scheme_builtin.h
diff --git a/src/scheme/Makefile b/src/scheme/Makefile
new file mode 100644
index 00000000..ea94c1c0
--- /dev/null
+++ b/src/scheme/Makefile
@@ -0,0 +1,20 @@
+all: ao_scheme_builtin.h ao_scheme_const.h test/ao_scheme_test
+
+clean:
+	+cd make-const && make clean
+	+cd test && make clean
+	rm -f ao_scheme_const.h ao_scheme_builtin.h
+
+ao_scheme_const.h: ao_scheme_const.lisp make-const/ao_scheme_make_const
+	make-const/ao_scheme_make_const -o $@ ao_scheme_const.lisp
+
+ao_scheme_builtin.h: ao_scheme_make_builtin ao_scheme_builtin.txt
+	nickle ao_scheme_make_builtin ao_scheme_builtin.txt > $@
+
+make-const/ao_scheme_make_const: FRC ao_scheme_builtin.h
+	+cd make-const && make ao_scheme_make_const
+
+test/ao_scheme_test: FRC ao_scheme_const.h ao_scheme_builtin.h
+	+cd test && make ao_scheme_test
+
+FRC:
diff --git a/src/scheme/Makefile-inc b/src/scheme/Makefile-inc
new file mode 100644
index 00000000..d23ee3d7
--- /dev/null
+++ b/src/scheme/Makefile-inc
@@ -0,0 +1,24 @@
+SCHEME_SRCS=\
+	ao_scheme_mem.c \
+	ao_scheme_cons.c \
+	ao_scheme_string.c \
+	ao_scheme_atom.c \
+	ao_scheme_int.c \
+	ao_scheme_poly.c \
+	ao_scheme_bool.c \
+	ao_scheme_float.c \
+	ao_scheme_builtin.c \
+	ao_scheme_read.c \
+	ao_scheme_frame.c \
+	ao_scheme_lambda.c \
+	ao_scheme_eval.c \
+	ao_scheme_rep.c \
+	ao_scheme_save.c \
+	ao_scheme_stack.c \
+	ao_scheme_error.c 
+
+SCHEME_HDRS=\
+	ao_scheme.h \
+	ao_scheme_os.h \
+	ao_scheme_read.h \
+	ao_scheme_builtin.h
diff --git a/src/scheme/Makefile-scheme b/src/scheme/Makefile-scheme
new file mode 100644
index 00000000..b9018e19
--- /dev/null
+++ b/src/scheme/Makefile-scheme
@@ -0,0 +1,4 @@
+include ../scheme/Makefile-inc
+
+ao_scheme_const.h: $(SCHEME_SRCS) $(SCHEME_HDRS)
+	+cd ../scheme && make $@
diff --git a/src/scheme/README b/src/scheme/README
new file mode 100644
index 00000000..98932b44
--- /dev/null
+++ b/src/scheme/README
@@ -0,0 +1,10 @@
+This follows the R7RS with the following known exceptions:
+
+* No vectors or bytevectors
+* Characters are just numbers
+* No dynamic-wind or exceptions
+* No environments
+* No ports
+* No syntax-rules; (have classic macros)
+* No record types
+* No libraries
diff --git a/src/scheme/ao_scheme.h b/src/scheme/ao_scheme.h
new file mode 100644
index 00000000..4589f8a5
--- /dev/null
+++ b/src/scheme/ao_scheme.h
@@ -0,0 +1,928 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#ifndef _AO_SCHEME_H_
+#define _AO_SCHEME_H_
+
+#define DBG_MEM		0
+#define DBG_EVAL	0
+#define DBG_READ	0
+#define DBG_FREE_CONS	0
+#define NDEBUG		1
+
+#include <stdint.h>
+#include <string.h>
+#include <ao_scheme_os.h>
+#ifndef __BYTE_ORDER
+#include <endian.h>
+#endif
+
+typedef uint16_t	ao_poly;
+typedef int16_t		ao_signed_poly;
+
+#ifdef AO_SCHEME_SAVE
+
+struct ao_scheme_os_save {
+	ao_poly		atoms;
+	ao_poly		globals;
+	uint16_t	const_checksum;
+	uint16_t	const_checksum_inv;
+};
+
+#define AO_SCHEME_POOL_EXTRA	(sizeof(struct ao_scheme_os_save))
+#define AO_SCHEME_POOL	((int) (AO_SCHEME_POOL_TOTAL - AO_SCHEME_POOL_EXTRA))
+
+int
+ao_scheme_os_save(void);
+
+int
+ao_scheme_os_restore_save(struct ao_scheme_os_save *save, int offset);
+
+int
+ao_scheme_os_restore(void);
+
+#endif
+
+#ifdef AO_SCHEME_MAKE_CONST
+#define AO_SCHEME_POOL_CONST	16384
+extern uint8_t ao_scheme_const[AO_SCHEME_POOL_CONST] __attribute__((aligned(4)));
+#define ao_scheme_pool ao_scheme_const
+#define AO_SCHEME_POOL AO_SCHEME_POOL_CONST
+
+#define _atom(n) ao_scheme_atom_poly(ao_scheme_atom_intern(n))
+#define _bool(v) ao_scheme_bool_poly(ao_scheme_bool_get(v))
+
+#define _ao_scheme_bool_true	_bool(1)
+#define _ao_scheme_bool_false	_bool(0)
+
+#define _ao_scheme_atom_eof	_atom("eof")
+#define _ao_scheme_atom_else	_atom("else")
+
+#define AO_SCHEME_BUILTIN_ATOMS
+#include "ao_scheme_builtin.h"
+
+#else
+#include "ao_scheme_const.h"
+#ifndef AO_SCHEME_POOL
+#define AO_SCHEME_POOL	3072
+#endif
+extern uint8_t		ao_scheme_pool[AO_SCHEME_POOL + AO_SCHEME_POOL_EXTRA] __attribute__((aligned(4)));
+#endif
+
+/* Primitive types */
+#define AO_SCHEME_CONS		0
+#define AO_SCHEME_INT		1
+#define AO_SCHEME_STRING	2
+#define AO_SCHEME_OTHER		3
+
+#define AO_SCHEME_TYPE_MASK	0x0003
+#define AO_SCHEME_TYPE_SHIFT	2
+#define AO_SCHEME_REF_MASK	0x7ffc
+#define AO_SCHEME_CONST		0x8000
+
+/* These have a type value at the start of the struct */
+#define AO_SCHEME_ATOM		4
+#define AO_SCHEME_BUILTIN	5
+#define AO_SCHEME_FRAME		6
+#define AO_SCHEME_FRAME_VALS	7
+#define AO_SCHEME_LAMBDA	8
+#define AO_SCHEME_STACK		9
+#define AO_SCHEME_BOOL		10
+#define AO_SCHEME_BIGINT	11
+#define AO_SCHEME_FLOAT		12
+#define AO_SCHEME_NUM_TYPE	13
+
+/* Leave two bits for types to use as they please */
+#define AO_SCHEME_OTHER_TYPE_MASK	0x3f
+
+#define AO_SCHEME_NIL	0
+
+extern uint16_t		ao_scheme_top;
+
+#define AO_SCHEME_OOM			0x01
+#define AO_SCHEME_DIVIDE_BY_ZERO	0x02
+#define AO_SCHEME_INVALID		0x04
+#define AO_SCHEME_UNDEFINED		0x08
+#define AO_SCHEME_REDEFINED		0x10
+#define AO_SCHEME_EOF			0x20
+#define AO_SCHEME_EXIT			0x40
+
+extern uint8_t		ao_scheme_exception;
+
+static inline int
+ao_scheme_is_const(ao_poly poly) {
+	return poly & AO_SCHEME_CONST;
+}
+
+#define AO_SCHEME_IS_CONST(a)	(ao_scheme_const <= ((uint8_t *) (a)) && ((uint8_t *) (a)) < ao_scheme_const + AO_SCHEME_POOL_CONST)
+#define AO_SCHEME_IS_POOL(a)	(ao_scheme_pool <= ((uint8_t *) (a)) && ((uint8_t *) (a)) < ao_scheme_pool + AO_SCHEME_POOL)
+#define AO_SCHEME_IS_INT(p)	(ao_scheme_poly_base_type(p) == AO_SCHEME_INT)
+
+void *
+ao_scheme_ref(ao_poly poly);
+
+ao_poly
+ao_scheme_poly(const void *addr, ao_poly type);
+
+struct ao_scheme_type {
+	int	(*size)(void *addr);
+	void	(*mark)(void *addr);
+	void	(*move)(void *addr);
+	char	name[];
+};
+
+struct ao_scheme_cons {
+	ao_poly		car;
+	ao_poly		cdr;
+};
+
+struct ao_scheme_atom {
+	uint8_t		type;
+	uint8_t		pad[1];
+	ao_poly		next;
+	char		name[];
+};
+
+struct ao_scheme_val {
+	ao_poly		atom;
+	ao_poly		val;
+};
+
+struct ao_scheme_frame_vals {
+	uint8_t			type;
+	uint8_t			size;
+	struct ao_scheme_val	vals[];
+};
+
+struct ao_scheme_frame {
+	uint8_t			type;
+	uint8_t			num;
+	ao_poly			prev;
+	ao_poly			vals;
+};
+
+struct ao_scheme_bool {
+	uint8_t			type;
+	uint8_t			value;
+	uint16_t		pad;
+};
+
+struct ao_scheme_bigint {
+	uint32_t		value;
+};
+
+struct ao_scheme_float {
+	uint8_t			type;
+	uint8_t			pad1;
+	uint16_t		pad2;
+	float			value;
+};
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+static inline uint32_t
+ao_scheme_int_bigint(int32_t i) {
+	return AO_SCHEME_BIGINT | (i << 8);
+}
+static inline int32_t
+ao_scheme_bigint_int(uint32_t bi) {
+	return (int32_t) bi >> 8;
+}
+#else
+static inline uint32_t
+ao_scheme_int_bigint(int32_t i) {
+	return (uint32_t) (i & 0xffffff) | (AO_SCHEME_BIGINT << 24);
+}
+static inlint int32_t
+ao_scheme_bigint_int(uint32_t bi) {
+	return (int32_t) (bi << 8) >> 8;
+}
+#endif
+
+#define AO_SCHEME_MIN_INT	(-(1 << (15 - AO_SCHEME_TYPE_SHIFT)))
+#define AO_SCHEME_MAX_INT	((1 << (15 - AO_SCHEME_TYPE_SHIFT)) - 1)
+#define AO_SCHEME_MIN_BIGINT	(-(1 << 24))
+#define AO_SCHEME_MAX_BIGINT	((1 << 24) - 1)
+
+#define AO_SCHEME_NOT_INTEGER	0x7fffffff
+
+/* Set on type when the frame escapes the lambda */
+#define AO_SCHEME_FRAME_MARK	0x80
+#define AO_SCHEME_FRAME_PRINT	0x40
+
+static inline int ao_scheme_frame_marked(struct ao_scheme_frame *f) {
+	return f->type & AO_SCHEME_FRAME_MARK;
+}
+
+static inline struct ao_scheme_frame *
+ao_scheme_poly_frame(ao_poly poly) {
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_frame_poly(struct ao_scheme_frame *frame) {
+	return ao_scheme_poly(frame, AO_SCHEME_OTHER);
+}
+
+static inline struct ao_scheme_frame_vals *
+ao_scheme_poly_frame_vals(ao_poly poly) {
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_frame_vals_poly(struct ao_scheme_frame_vals *vals) {
+	return ao_scheme_poly(vals, AO_SCHEME_OTHER);
+}
+
+enum eval_state {
+	eval_sexpr,		/* Evaluate an sexpr */
+	eval_val,		/* Value computed */
+	eval_formal,		/* Formal computed */
+	eval_exec,		/* Start a lambda evaluation */
+	eval_apply,		/* Execute apply */
+	eval_cond,		/* Start next cond clause */
+	eval_cond_test,		/* Check cond condition */
+	eval_begin,		/* Start next begin entry */
+	eval_while,		/* Start while condition */
+	eval_while_test,	/* Check while condition */
+	eval_macro,		/* Finished with macro generation */
+};
+
+struct ao_scheme_stack {
+	uint8_t			type;		/* AO_SCHEME_STACK */
+	uint8_t			state;		/* enum eval_state */
+	ao_poly			prev;		/* previous stack frame */
+	ao_poly			sexprs;		/* expressions to evaluate */
+	ao_poly			values;		/* values computed */
+	ao_poly			values_tail;	/* end of the values list for easy appending */
+	ao_poly			frame;		/* current lookup frame */
+	ao_poly			list;		/* most recent function call */
+};
+
+#define AO_SCHEME_STACK_MARK	0x80	/* set on type when a reference has been taken */
+#define AO_SCHEME_STACK_PRINT	0x40	/* stack is being printed */
+
+static inline int ao_scheme_stack_marked(struct ao_scheme_stack *s) {
+	return s->type & AO_SCHEME_STACK_MARK;
+}
+
+static inline void ao_scheme_stack_mark(struct ao_scheme_stack *s) {
+	s->type |= AO_SCHEME_STACK_MARK;
+}
+
+static inline struct ao_scheme_stack *
+ao_scheme_poly_stack(ao_poly p)
+{
+	return ao_scheme_ref(p);
+}
+
+static inline ao_poly
+ao_scheme_stack_poly(struct ao_scheme_stack *stack)
+{
+	return ao_scheme_poly(stack, AO_SCHEME_OTHER);
+}
+
+extern ao_poly			ao_scheme_v;
+
+#define AO_SCHEME_FUNC_LAMBDA		0
+#define AO_SCHEME_FUNC_NLAMBDA		1
+#define AO_SCHEME_FUNC_MACRO		2
+
+#define AO_SCHEME_FUNC_FREE_ARGS	0x80
+#define AO_SCHEME_FUNC_MASK		0x7f
+
+#define AO_SCHEME_FUNC_F_LAMBDA		(AO_SCHEME_FUNC_FREE_ARGS | AO_SCHEME_FUNC_LAMBDA)
+#define AO_SCHEME_FUNC_F_NLAMBDA	(AO_SCHEME_FUNC_FREE_ARGS | AO_SCHEME_FUNC_NLAMBDA)
+#define AO_SCHEME_FUNC_F_MACRO		(AO_SCHEME_FUNC_FREE_ARGS | AO_SCHEME_FUNC_MACRO)
+
+struct ao_scheme_builtin {
+	uint8_t		type;
+	uint8_t		args;
+	uint16_t	func;
+};
+
+#define AO_SCHEME_BUILTIN_ID
+#include "ao_scheme_builtin.h"
+
+typedef ao_poly (*ao_scheme_func_t)(struct ao_scheme_cons *cons);
+
+extern const ao_scheme_func_t	ao_scheme_builtins[];
+
+static inline ao_scheme_func_t
+ao_scheme_func(struct ao_scheme_builtin *b)
+{
+	return ao_scheme_builtins[b->func];
+}
+
+struct ao_scheme_lambda {
+	uint8_t		type;
+	uint8_t		args;
+	ao_poly		code;
+	ao_poly		frame;
+};
+
+static inline struct ao_scheme_lambda *
+ao_scheme_poly_lambda(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_lambda_poly(struct ao_scheme_lambda *lambda)
+{
+	return ao_scheme_poly(lambda, AO_SCHEME_OTHER);
+}
+
+static inline void *
+ao_scheme_poly_other(ao_poly poly) {
+	return ao_scheme_ref(poly);
+}
+
+static inline uint8_t
+ao_scheme_other_type(void *other) {
+#if DBG_MEM
+	if ((*((uint8_t *) other) & AO_SCHEME_OTHER_TYPE_MASK) >= AO_SCHEME_NUM_TYPE)
+		ao_scheme_abort();
+#endif
+	return *((uint8_t *) other) & AO_SCHEME_OTHER_TYPE_MASK;
+}
+
+static inline ao_poly
+ao_scheme_other_poly(const void *other)
+{
+	return ao_scheme_poly(other, AO_SCHEME_OTHER);
+}
+
+static inline int
+ao_scheme_size_round(int size)
+{
+	return (size + 3) & ~3;
+}
+
+static inline int
+ao_scheme_size(const struct ao_scheme_type *type, void *addr)
+{
+	return ao_scheme_size_round(type->size(addr));
+}
+
+#define AO_SCHEME_OTHER_POLY(other) ((ao_poly)(other) + AO_SCHEME_OTHER)
+
+static inline int ao_scheme_poly_base_type(ao_poly poly) {
+	return poly & AO_SCHEME_TYPE_MASK;
+}
+
+static inline int ao_scheme_poly_type(ao_poly poly) {
+	int	type = poly & AO_SCHEME_TYPE_MASK;
+	if (type == AO_SCHEME_OTHER)
+		return ao_scheme_other_type(ao_scheme_poly_other(poly));
+	return type;
+}
+
+static inline int
+ao_scheme_is_cons(ao_poly poly) {
+	return (ao_scheme_poly_base_type(poly) == AO_SCHEME_CONS);
+}
+
+static inline int
+ao_scheme_is_pair(ao_poly poly) {
+	return poly != AO_SCHEME_NIL && (ao_scheme_poly_base_type(poly) == AO_SCHEME_CONS);
+}
+
+static inline struct ao_scheme_cons *
+ao_scheme_poly_cons(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_cons_poly(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_poly(cons, AO_SCHEME_CONS);
+}
+
+static inline int32_t
+ao_scheme_poly_int(ao_poly poly)
+{
+	return (int32_t) ((ao_signed_poly) poly >> AO_SCHEME_TYPE_SHIFT);
+}
+
+static inline ao_poly
+ao_scheme_int_poly(int32_t i)
+{
+	return ((ao_poly) i << 2) | AO_SCHEME_INT;
+}
+
+static inline struct ao_scheme_bigint *
+ao_scheme_poly_bigint(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_bigint_poly(struct ao_scheme_bigint *bi)
+{
+	return ao_scheme_poly(bi, AO_SCHEME_OTHER);
+}
+
+static inline char *
+ao_scheme_poly_string(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_string_poly(char *s)
+{
+	return ao_scheme_poly(s, AO_SCHEME_STRING);
+}
+
+static inline struct ao_scheme_atom *
+ao_scheme_poly_atom(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_atom_poly(struct ao_scheme_atom *a)
+{
+	return ao_scheme_poly(a, AO_SCHEME_OTHER);
+}
+
+static inline struct ao_scheme_builtin *
+ao_scheme_poly_builtin(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_builtin_poly(struct ao_scheme_builtin *b)
+{
+	return ao_scheme_poly(b, AO_SCHEME_OTHER);
+}
+
+static inline ao_poly
+ao_scheme_bool_poly(struct ao_scheme_bool *b)
+{
+	return ao_scheme_poly(b, AO_SCHEME_OTHER);
+}
+
+static inline struct ao_scheme_bool *
+ao_scheme_poly_bool(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+static inline ao_poly
+ao_scheme_float_poly(struct ao_scheme_float *f)
+{
+	return ao_scheme_poly(f, AO_SCHEME_OTHER);
+}
+
+static inline struct ao_scheme_float *
+ao_scheme_poly_float(ao_poly poly)
+{
+	return ao_scheme_ref(poly);
+}
+
+float
+ao_scheme_poly_number(ao_poly p);
+
+/* memory functions */
+
+extern int ao_scheme_collects[2];
+extern int ao_scheme_freed[2];
+extern int ao_scheme_loops[2];
+
+/* returns 1 if the object was already marked */
+int
+ao_scheme_mark(const struct ao_scheme_type *type, void *addr);
+
+/* returns 1 if the object was already marked */
+int
+ao_scheme_mark_memory(const struct ao_scheme_type *type, void *addr);
+
+void *
+ao_scheme_move_map(void *addr);
+
+/* returns 1 if the object was already moved */
+int
+ao_scheme_move(const struct ao_scheme_type *type, void **ref);
+
+/* returns 1 if the object was already moved */
+int
+ao_scheme_move_memory(const struct ao_scheme_type *type, void **ref);
+
+void *
+ao_scheme_alloc(int size);
+
+#define AO_SCHEME_COLLECT_FULL		1
+#define AO_SCHEME_COLLECT_INCREMENTAL	0
+
+int
+ao_scheme_collect(uint8_t style);
+
+#if DBG_FREE_CONS
+void
+ao_scheme_cons_check(struct ao_scheme_cons *cons);
+#endif
+
+void
+ao_scheme_cons_stash(int id, struct ao_scheme_cons *cons);
+
+struct ao_scheme_cons *
+ao_scheme_cons_fetch(int id);
+
+void
+ao_scheme_poly_stash(int id, ao_poly poly);
+
+ao_poly
+ao_scheme_poly_fetch(int id);
+
+void
+ao_scheme_string_stash(int id, char *string);
+
+char *
+ao_scheme_string_fetch(int id);
+
+static inline void
+ao_scheme_stack_stash(int id, struct ao_scheme_stack *stack) {
+	ao_scheme_poly_stash(id, ao_scheme_stack_poly(stack));
+}
+
+static inline struct ao_scheme_stack *
+ao_scheme_stack_fetch(int id) {
+	return ao_scheme_poly_stack(ao_scheme_poly_fetch(id));
+}
+
+void
+ao_scheme_frame_stash(int id, struct ao_scheme_frame *frame);
+
+struct ao_scheme_frame *
+ao_scheme_frame_fetch(int id);
+
+/* bool */
+
+extern const struct ao_scheme_type ao_scheme_bool_type;
+
+void
+ao_scheme_bool_write(ao_poly v);
+
+#ifdef AO_SCHEME_MAKE_CONST
+struct ao_scheme_bool	*ao_scheme_true, *ao_scheme_false;
+
+struct ao_scheme_bool *
+ao_scheme_bool_get(uint8_t value);
+#endif
+
+/* cons */
+extern const struct ao_scheme_type ao_scheme_cons_type;
+
+struct ao_scheme_cons *
+ao_scheme_cons_cons(ao_poly car, ao_poly cdr);
+
+/* Return a cons or NULL for a proper list, else error */
+struct ao_scheme_cons *
+ao_scheme_cons_cdr(struct ao_scheme_cons *cons);
+
+ao_poly
+ao_scheme__cons(ao_poly car, ao_poly cdr);
+
+extern struct ao_scheme_cons *ao_scheme_cons_free_list;
+
+void
+ao_scheme_cons_free(struct ao_scheme_cons *cons);
+
+void
+ao_scheme_cons_write(ao_poly);
+
+void
+ao_scheme_cons_display(ao_poly);
+
+int
+ao_scheme_cons_length(struct ao_scheme_cons *cons);
+
+/* string */
+extern const struct ao_scheme_type ao_scheme_string_type;
+
+char *
+ao_scheme_string_copy(char *a);
+
+char *
+ao_scheme_string_cat(char *a, char *b);
+
+ao_poly
+ao_scheme_string_pack(struct ao_scheme_cons *cons);
+
+ao_poly
+ao_scheme_string_unpack(char *a);
+
+void
+ao_scheme_string_write(ao_poly s);
+
+void
+ao_scheme_string_display(ao_poly s);
+
+/* atom */
+extern const struct ao_scheme_type ao_scheme_atom_type;
+
+extern struct ao_scheme_atom	*ao_scheme_atoms;
+extern struct ao_scheme_frame	*ao_scheme_frame_global;
+extern struct ao_scheme_frame	*ao_scheme_frame_current;
+
+void
+ao_scheme_atom_write(ao_poly a);
+
+struct ao_scheme_atom *
+ao_scheme_atom_intern(char *name);
+
+ao_poly *
+ao_scheme_atom_ref(ao_poly atom, struct ao_scheme_frame **frame_ref);
+
+ao_poly
+ao_scheme_atom_get(ao_poly atom);
+
+ao_poly
+ao_scheme_atom_set(ao_poly atom, ao_poly val);
+
+ao_poly
+ao_scheme_atom_def(ao_poly atom, ao_poly val);
+
+/* int */
+void
+ao_scheme_int_write(ao_poly i);
+
+int32_t
+ao_scheme_poly_integer(ao_poly p);
+
+ao_poly
+ao_scheme_integer_poly(int32_t i);
+
+static inline int
+ao_scheme_integer_typep(uint8_t t)
+{
+	return (t == AO_SCHEME_INT) || (t == AO_SCHEME_BIGINT);
+}
+
+void
+ao_scheme_bigint_write(ao_poly i);
+
+extern const struct ao_scheme_type	ao_scheme_bigint_type;
+/* prim */
+void
+ao_scheme_poly_write(ao_poly p);
+
+void
+ao_scheme_poly_display(ao_poly p);
+
+int
+ao_scheme_poly_mark(ao_poly p, uint8_t note_cons);
+
+/* returns 1 if the object has already been moved */
+int
+ao_scheme_poly_move(ao_poly *p, uint8_t note_cons);
+
+/* eval */
+
+void
+ao_scheme_eval_clear_globals(void);
+
+int
+ao_scheme_eval_restart(void);
+
+ao_poly
+ao_scheme_eval(ao_poly p);
+
+ao_poly
+ao_scheme_set_cond(struct ao_scheme_cons *cons);
+
+/* float */
+extern const struct ao_scheme_type ao_scheme_float_type;
+
+void
+ao_scheme_float_write(ao_poly p);
+
+ao_poly
+ao_scheme_float_get(float value);
+
+static inline uint8_t
+ao_scheme_number_typep(uint8_t t)
+{
+	return ao_scheme_integer_typep(t) || (t == AO_SCHEME_FLOAT);
+}
+
+float
+ao_scheme_poly_number(ao_poly p);
+
+/* builtin */
+void
+ao_scheme_builtin_write(ao_poly b);
+
+extern const struct ao_scheme_type ao_scheme_builtin_type;
+
+/* Check argument count */
+ao_poly
+ao_scheme_check_argc(ao_poly name, struct ao_scheme_cons *cons, int min, int max);
+
+/* Check argument type */
+ao_poly
+ao_scheme_check_argt(ao_poly name, struct ao_scheme_cons *cons, int argc, int type, int nil_ok);
+
+/* Fetch an arg (nil if off the end) */
+ao_poly
+ao_scheme_arg(struct ao_scheme_cons *cons, int argc);
+
+char *
+ao_scheme_args_name(uint8_t args);
+
+/* read */
+extern struct ao_scheme_cons	*ao_scheme_read_cons;
+extern struct ao_scheme_cons	*ao_scheme_read_cons_tail;
+extern struct ao_scheme_cons	*ao_scheme_read_stack;
+
+ao_poly
+ao_scheme_read(void);
+
+/* rep */
+ao_poly
+ao_scheme_read_eval_print(void);
+
+/* frame */
+extern const struct ao_scheme_type ao_scheme_frame_type;
+extern const struct ao_scheme_type ao_scheme_frame_vals_type;
+
+#define AO_SCHEME_FRAME_FREE	6
+
+extern struct ao_scheme_frame	*ao_scheme_frame_free_list[AO_SCHEME_FRAME_FREE];
+
+ao_poly
+ao_scheme_frame_mark(struct ao_scheme_frame *frame);
+
+ao_poly *
+ao_scheme_frame_ref(struct ao_scheme_frame *frame, ao_poly atom);
+
+struct ao_scheme_frame *
+ao_scheme_frame_new(int num);
+
+void
+ao_scheme_frame_free(struct ao_scheme_frame *frame);
+
+void
+ao_scheme_frame_bind(struct ao_scheme_frame *frame, int num, ao_poly atom, ao_poly val);
+
+ao_poly
+ao_scheme_frame_add(struct ao_scheme_frame *frame, ao_poly atom, ao_poly val);
+
+void
+ao_scheme_frame_write(ao_poly p);
+
+void
+ao_scheme_frame_init(void);
+
+/* lambda */
+extern const struct ao_scheme_type ao_scheme_lambda_type;
+
+extern const char * const ao_scheme_state_names[];
+
+struct ao_scheme_lambda *
+ao_scheme_lambda_new(ao_poly cons);
+
+void
+ao_scheme_lambda_write(ao_poly lambda);
+
+ao_poly
+ao_scheme_lambda_eval(void);
+
+/* stack */
+
+extern const struct ao_scheme_type ao_scheme_stack_type;
+extern struct ao_scheme_stack	*ao_scheme_stack;
+extern struct ao_scheme_stack	*ao_scheme_stack_free_list;
+
+void
+ao_scheme_stack_reset(struct ao_scheme_stack *stack);
+
+int
+ao_scheme_stack_push(void);
+
+void
+ao_scheme_stack_pop(void);
+
+void
+ao_scheme_stack_clear(void);
+
+void
+ao_scheme_stack_write(ao_poly stack);
+
+ao_poly
+ao_scheme_stack_eval(void);
+
+/* error */
+
+void
+ao_scheme_vprintf(char *format, va_list args);
+
+void
+ao_scheme_printf(char *format, ...);
+
+void
+ao_scheme_error_poly(char *name, ao_poly poly, ao_poly last);
+
+void
+ao_scheme_error_frame(int indent, char *name, struct ao_scheme_frame *frame);
+
+ao_poly
+ao_scheme_error(int error, char *format, ...);
+
+/* builtins */
+
+#define AO_SCHEME_BUILTIN_DECLS
+#include "ao_scheme_builtin.h"
+
+/* debugging macros */
+
+#if DBG_EVAL || DBG_READ || DBG_MEM
+#define DBG_CODE	1
+int ao_scheme_stack_depth;
+#define DBG_DO(a)	a
+#define DBG_INDENT()	do { int _s; for(_s = 0; _s < ao_scheme_stack_depth; _s++) printf("  "); } while(0)
+#define DBG_IN()	(++ao_scheme_stack_depth)
+#define DBG_OUT()	(--ao_scheme_stack_depth)
+#define DBG_RESET()	(ao_scheme_stack_depth = 0)
+#define DBG(...) 	ao_scheme_printf(__VA_ARGS__)
+#define DBGI(...)	do { printf("%4d: ", __LINE__); DBG_INDENT(); DBG(__VA_ARGS__); } while (0)
+#define DBG_CONS(a)	ao_scheme_cons_write(ao_scheme_cons_poly(a))
+#define DBG_POLY(a)	ao_scheme_poly_write(a)
+#define OFFSET(a)	((a) ? (int) ((uint8_t *) a - ao_scheme_pool) : -1)
+#define DBG_STACK()	ao_scheme_stack_write(ao_scheme_stack_poly(ao_scheme_stack))
+static inline void
+ao_scheme_frames_dump(void)
+{
+	struct ao_scheme_stack *s;
+	DBGI(".. current frame: "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	for (s = ao_scheme_stack; s; s = ao_scheme_poly_stack(s->prev)) {
+		DBGI(".. stack frame: "); DBG_POLY(s->frame); DBG("\n");
+	}
+}
+#define DBG_FRAMES()	ao_scheme_frames_dump()
+#else
+#define DBG_DO(a)
+#define DBG_INDENT()
+#define DBG_IN()
+#define DBG_OUT()
+#define DBG(...)
+#define DBGI(...)
+#define DBG_CONS(a)
+#define DBG_POLY(a)
+#define DBG_RESET()
+#define DBG_STACK()
+#define DBG_FRAMES()
+#endif
+
+#if DBG_READ
+#define RDBGI(...)	DBGI(__VA_ARGS__)
+#define RDBG_IN()	DBG_IN()
+#define RDBG_OUT()	DBG_OUT()
+#else
+#define RDBGI(...)
+#define RDBG_IN()
+#define RDBG_OUT()
+#endif
+
+#define DBG_MEM_START	1
+
+#if DBG_MEM
+
+#include <assert.h>
+extern int dbg_move_depth;
+#define MDBG_DUMP 1
+#define MDBG_OFFSET(a)	((a) ? (int) ((uint8_t *) (a) - ao_scheme_pool) : -1)
+
+extern int dbg_mem;
+
+#define MDBG_DO(a)	DBG_DO(a)
+#define MDBG_MOVE(...) do { if (dbg_mem) { int d; for (d = 0; d < dbg_move_depth; d++) printf ("  "); printf(__VA_ARGS__); } } while (0)
+#define MDBG_MORE(...) do { if (dbg_mem) printf(__VA_ARGS__); } while (0)
+#define MDBG_MOVE_IN()	(dbg_move_depth++)
+#define MDBG_MOVE_OUT()	(assert(--dbg_move_depth >= 0))
+
+#else
+
+#define MDBG_DO(a)
+#define MDBG_MOVE(...)
+#define MDBG_MORE(...)
+#define MDBG_MOVE_IN()
+#define MDBG_MOVE_OUT()
+
+#endif
+
+#endif /* _AO_SCHEME_H_ */
diff --git a/src/scheme/ao_scheme_atom.c b/src/scheme/ao_scheme_atom.c
new file mode 100644
index 00000000..cb32b7fe
--- /dev/null
+++ b/src/scheme/ao_scheme_atom.c
@@ -0,0 +1,167 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao_scheme.h"
+
+static int name_size(char *name)
+{
+	return sizeof(struct ao_scheme_atom) + strlen(name) + 1;
+}
+
+static int atom_size(void *addr)
+{
+	struct ao_scheme_atom	*atom = addr;
+	if (!atom)
+		return 0;
+	return name_size(atom->name);
+}
+
+static void atom_mark(void *addr)
+{
+	struct ao_scheme_atom	*atom = addr;
+
+	for (;;) {
+		atom = ao_scheme_poly_atom(atom->next);
+		if (!atom)
+			break;
+		if (ao_scheme_mark_memory(&ao_scheme_atom_type, atom))
+			break;
+	}
+}
+
+static void atom_move(void *addr)
+{
+	struct ao_scheme_atom	*atom = addr;
+	int			ret;
+
+	for (;;) {
+		struct ao_scheme_atom *next = ao_scheme_poly_atom(atom->next);
+
+		if (!next)
+			break;
+		ret = ao_scheme_move_memory(&ao_scheme_atom_type, (void **) &next);
+		if (next != ao_scheme_poly_atom(atom->next))
+			atom->next = ao_scheme_atom_poly(next);
+		if (ret)
+			break;
+		atom = next;
+	}
+}
+
+const struct ao_scheme_type ao_scheme_atom_type = {
+	.mark = atom_mark,
+	.size = atom_size,
+	.move = atom_move,
+	.name = "atom"
+};
+
+struct ao_scheme_atom	*ao_scheme_atoms;
+
+struct ao_scheme_atom *
+ao_scheme_atom_intern(char *name)
+{
+	struct ao_scheme_atom	*atom;
+
+	for (atom = ao_scheme_atoms; atom; atom = ao_scheme_poly_atom(atom->next)) {
+		if (!strcmp(atom->name, name))
+			return atom;
+	}
+#ifdef ao_builtin_atoms
+	for (atom = ao_scheme_poly_atom(ao_builtin_atoms); atom; atom = ao_scheme_poly_atom(atom->next)) {
+		if (!strcmp(atom->name, name))
+			return atom;
+	}
+#endif
+	ao_scheme_string_stash(0, name);
+	atom = ao_scheme_alloc(name_size(name));
+	name = ao_scheme_string_fetch(0);
+	if (atom) {
+		atom->type = AO_SCHEME_ATOM;
+		atom->next = ao_scheme_atom_poly(ao_scheme_atoms);
+		ao_scheme_atoms = atom;
+		strcpy(atom->name, name);
+	}
+	return atom;
+}
+
+ao_poly *
+ao_scheme_atom_ref(ao_poly atom, struct ao_scheme_frame **frame_ref)
+{
+	ao_poly	*ref;
+	struct ao_scheme_frame *frame;
+
+	for (frame = ao_scheme_frame_current; frame; frame = ao_scheme_poly_frame(frame->prev)) {
+		ref = ao_scheme_frame_ref(frame, atom);
+		if (ref) {
+			if (frame_ref)
+				*frame_ref = frame;
+			return ref;
+		}
+	}
+	ref = ao_scheme_frame_ref(ao_scheme_frame_global, atom);
+	if (ref)
+		if (frame_ref)
+			*frame_ref = ao_scheme_frame_global;
+	return ref;
+}
+
+ao_poly
+ao_scheme_atom_get(ao_poly atom)
+{
+	ao_poly *ref = ao_scheme_atom_ref(atom, NULL);
+
+#ifdef ao_builtin_frame
+	if (!ref)
+		ref = ao_scheme_frame_ref(ao_scheme_poly_frame(ao_builtin_frame), atom);
+#endif
+	if (ref)
+		return *ref;
+	return ao_scheme_error(AO_SCHEME_UNDEFINED, "undefined atom %s", ao_scheme_poly_atom(atom)->name);
+}
+
+ao_poly
+ao_scheme_atom_set(ao_poly atom, ao_poly val)
+{
+	ao_poly *ref = ao_scheme_atom_ref(atom, NULL);
+
+	if (!ref)
+		return ao_scheme_error(AO_SCHEME_UNDEFINED, "undefined atom %s", ao_scheme_poly_atom(atom)->name);
+	*ref = val;
+	return val;
+}
+
+ao_poly
+ao_scheme_atom_def(ao_poly atom, ao_poly val)
+{
+	struct ao_scheme_frame	*frame;
+	ao_poly *ref = ao_scheme_atom_ref(atom, &frame);
+
+	if (ref) {
+		if (frame == ao_scheme_frame_current)
+			return ao_scheme_error(AO_SCHEME_REDEFINED, "attempt to redefine atom %s", ao_scheme_poly_atom(atom)->name);
+		*ref = val;
+		return val;
+	}
+	return ao_scheme_frame_add(ao_scheme_frame_current ? ao_scheme_frame_current : ao_scheme_frame_global, atom, val);
+}
+
+void
+ao_scheme_atom_write(ao_poly a)
+{
+	struct ao_scheme_atom *atom = ao_scheme_poly_atom(a);
+	printf("%s", atom->name);
+}
diff --git a/src/scheme/ao_scheme_bool.c b/src/scheme/ao_scheme_bool.c
new file mode 100644
index 00000000..c1e880ca
--- /dev/null
+++ b/src/scheme/ao_scheme_bool.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright © 2017 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+static void bool_mark(void *addr)
+{
+	(void) addr;
+}
+
+static int bool_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_bool);
+}
+
+static void bool_move(void *addr)
+{
+	(void) addr;
+}
+
+const struct ao_scheme_type ao_scheme_bool_type = {
+	.mark = bool_mark,
+	.size = bool_size,
+	.move = bool_move,
+	.name = "bool"
+};
+
+void
+ao_scheme_bool_write(ao_poly v)
+{
+	struct ao_scheme_bool	*b = ao_scheme_poly_bool(v);
+
+	if (b->value)
+		printf("#t");
+	else
+		printf("#f");
+}
+
+#ifdef AO_SCHEME_MAKE_CONST
+
+struct ao_scheme_bool	*ao_scheme_true, *ao_scheme_false;
+
+struct ao_scheme_bool *
+ao_scheme_bool_get(uint8_t value)
+{
+	struct ao_scheme_bool	**b;
+
+	if (value)
+		b = &ao_scheme_true;
+	else
+		b = &ao_scheme_false;
+
+	if (!*b) {
+		*b = ao_scheme_alloc(sizeof (struct ao_scheme_bool));
+		(*b)->type = AO_SCHEME_BOOL;
+		(*b)->value = value;
+	}
+	return *b;
+}
+
+#endif
diff --git a/src/scheme/ao_scheme_builtin.c b/src/scheme/ao_scheme_builtin.c
new file mode 100644
index 00000000..49f218f6
--- /dev/null
+++ b/src/scheme/ao_scheme_builtin.c
@@ -0,0 +1,868 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <limits.h>
+#include <math.h>
+
+static int
+builtin_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_builtin);
+}
+
+static void
+builtin_mark(void *addr)
+{
+	(void) addr;
+}
+
+static void
+builtin_move(void *addr)
+{
+	(void) addr;
+}
+
+const struct ao_scheme_type ao_scheme_builtin_type = {
+	.size = builtin_size,
+	.mark = builtin_mark,
+	.move = builtin_move
+};
+
+#ifdef AO_SCHEME_MAKE_CONST
+
+#define AO_SCHEME_BUILTIN_CASENAME
+#include "ao_scheme_builtin.h"
+
+char *ao_scheme_args_name(uint8_t args) {
+	args &= AO_SCHEME_FUNC_MASK;
+	switch (args) {
+	case AO_SCHEME_FUNC_LAMBDA: return ao_scheme_poly_atom(_ao_scheme_atom_lambda)->name;
+	case AO_SCHEME_FUNC_NLAMBDA: return ao_scheme_poly_atom(_ao_scheme_atom_nlambda)->name;
+	case AO_SCHEME_FUNC_MACRO: return ao_scheme_poly_atom(_ao_scheme_atom_macro)->name;
+	default: return "???";
+	}
+}
+#else
+
+#define AO_SCHEME_BUILTIN_ARRAYNAME
+#include "ao_scheme_builtin.h"
+
+static char *
+ao_scheme_builtin_name(enum ao_scheme_builtin_id b) {
+	if (b < _builtin_last)
+		return ao_scheme_poly_atom(builtin_names[b])->name;
+	return "???";
+}
+
+static const ao_poly ao_scheme_args_atoms[] = {
+	[AO_SCHEME_FUNC_LAMBDA] = _ao_scheme_atom_lambda,
+	[AO_SCHEME_FUNC_NLAMBDA] = _ao_scheme_atom_nlambda,
+	[AO_SCHEME_FUNC_MACRO] = _ao_scheme_atom_macro,
+};
+
+char *
+ao_scheme_args_name(uint8_t args)
+{
+	args &= AO_SCHEME_FUNC_MASK;
+	if (args < sizeof ao_scheme_args_atoms / sizeof ao_scheme_args_atoms[0])
+		return ao_scheme_poly_atom(ao_scheme_args_atoms[args])->name;
+	return "(unknown)";
+}
+#endif
+
+void
+ao_scheme_builtin_write(ao_poly b)
+{
+	struct ao_scheme_builtin *builtin = ao_scheme_poly_builtin(b);
+	printf("%s", ao_scheme_builtin_name(builtin->func));
+}
+
+ao_poly
+ao_scheme_check_argc(ao_poly name, struct ao_scheme_cons *cons, int min, int max)
+{
+	int	argc = 0;
+
+	while (cons && argc <= max) {
+		argc++;
+		cons = ao_scheme_cons_cdr(cons);
+	}
+	if (argc < min || argc > max)
+		return ao_scheme_error(AO_SCHEME_INVALID, "%s: invalid arg count", ao_scheme_poly_atom(name)->name);
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_arg(struct ao_scheme_cons *cons, int argc)
+{
+	if (!cons)
+		return AO_SCHEME_NIL;
+	while (argc--) {
+		if (!cons)
+			return AO_SCHEME_NIL;
+		cons = ao_scheme_cons_cdr(cons);
+	}
+	return cons->car;
+}
+
+ao_poly
+ao_scheme_check_argt(ao_poly name, struct ao_scheme_cons *cons, int argc, int type, int nil_ok)
+{
+	ao_poly car = ao_scheme_arg(cons, argc);
+
+	if ((!car && !nil_ok) || ao_scheme_poly_type(car) != type)
+		return ao_scheme_error(AO_SCHEME_INVALID, "%s: arg %d invalid type %v", ao_scheme_poly_atom(name)->name, argc, car);
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_car(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_car, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_car, cons, 0, AO_SCHEME_CONS, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_poly_cons(cons->car)->car;
+}
+
+ao_poly
+ao_scheme_do_cdr(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_cdr, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_cdr, cons, 0, AO_SCHEME_CONS, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_poly_cons(cons->car)->cdr;
+}
+
+ao_poly
+ao_scheme_do_cons(struct ao_scheme_cons *cons)
+{
+	ao_poly	car, cdr;
+	if(!ao_scheme_check_argc(_ao_scheme_atom_cons, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	car = ao_scheme_arg(cons, 0);
+	cdr = ao_scheme_arg(cons, 1);
+	return ao_scheme__cons(car, cdr);
+}
+
+ao_poly
+ao_scheme_do_last(struct ao_scheme_cons *cons)
+{
+	struct ao_scheme_cons	*list;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_last, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_last, cons, 0, AO_SCHEME_CONS, 1))
+		return AO_SCHEME_NIL;
+	for (list = ao_scheme_poly_cons(ao_scheme_arg(cons, 0));
+	     list;
+	     list = ao_scheme_cons_cdr(list))
+	{
+		if (!list->cdr)
+			return list->car;
+	}
+	return AO_SCHEME_NIL;
+}
+
+ao_poly
+ao_scheme_do_length(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_length, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_length, cons, 0, AO_SCHEME_CONS, 1))
+		return AO_SCHEME_NIL;
+	return ao_scheme_int_poly(ao_scheme_cons_length(ao_scheme_poly_cons(ao_scheme_arg(cons, 0))));
+}
+
+ao_poly
+ao_scheme_do_quote(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_quote, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	return ao_scheme_arg(cons, 0);
+}
+
+ao_poly
+ao_scheme_do_set(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_set, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_set, cons, 0, AO_SCHEME_ATOM, 0))
+		return AO_SCHEME_NIL;
+
+	return ao_scheme_atom_set(ao_scheme_arg(cons, 0), ao_scheme_arg(cons, 1));
+}
+
+ao_poly
+ao_scheme_do_def(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_def, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_def, cons, 0, AO_SCHEME_ATOM, 0))
+		return AO_SCHEME_NIL;
+
+	return ao_scheme_atom_def(ao_scheme_arg(cons, 0), ao_scheme_arg(cons, 1));
+}
+
+ao_poly
+ao_scheme_do_setq(struct ao_scheme_cons *cons)
+{
+	ao_poly	name;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_set21, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	name = cons->car;
+	if (ao_scheme_poly_type(name) != AO_SCHEME_ATOM)
+		return ao_scheme_error(AO_SCHEME_INVALID, "set! of non-atom %v", name);
+	if (!ao_scheme_atom_ref(name, NULL))
+		return ao_scheme_error(AO_SCHEME_INVALID, "atom %v not defined", name);
+	return ao_scheme__cons(_ao_scheme_atom_set,
+			     ao_scheme__cons(ao_scheme__cons(_ao_scheme_atom_quote,
+							 ao_scheme__cons(name, AO_SCHEME_NIL)),
+					   cons->cdr));
+}
+
+ao_poly
+ao_scheme_do_cond(struct ao_scheme_cons *cons)
+{
+	ao_scheme_set_cond(cons);
+	return AO_SCHEME_NIL;
+}
+
+ao_poly
+ao_scheme_do_begin(struct ao_scheme_cons *cons)
+{
+	ao_scheme_stack->state = eval_begin;
+	ao_scheme_stack->sexprs = ao_scheme_cons_poly(cons);
+	return AO_SCHEME_NIL;
+}
+
+ao_poly
+ao_scheme_do_while(struct ao_scheme_cons *cons)
+{
+	ao_scheme_stack->state = eval_while;
+	ao_scheme_stack->sexprs = ao_scheme_cons_poly(cons);
+	return AO_SCHEME_NIL;
+}
+
+ao_poly
+ao_scheme_do_write(struct ao_scheme_cons *cons)
+{
+	ao_poly	val = AO_SCHEME_NIL;
+	while (cons) {
+		val = cons->car;
+		ao_scheme_poly_write(val);
+		cons = ao_scheme_cons_cdr(cons);
+		if (cons)
+			printf(" ");
+	}
+	printf("\n");
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_display(struct ao_scheme_cons *cons)
+{
+	ao_poly	val = AO_SCHEME_NIL;
+	while (cons) {
+		val = cons->car;
+		ao_scheme_poly_display(val);
+		cons = ao_scheme_cons_cdr(cons);
+	}
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_math(struct ao_scheme_cons *orig_cons, enum ao_scheme_builtin_id op)
+{
+	struct ao_scheme_cons *cons = cons;
+	ao_poly	ret = AO_SCHEME_NIL;
+
+	for (cons = orig_cons; cons; cons = ao_scheme_cons_cdr(cons)) {
+		ao_poly		car = cons->car;
+		uint8_t		rt = ao_scheme_poly_type(ret);
+		uint8_t		ct = ao_scheme_poly_type(car);
+
+		if (cons == orig_cons) {
+			ret = car;
+			if (cons->cdr == AO_SCHEME_NIL) {
+				switch (op) {
+				case builtin_minus:
+					if (ao_scheme_integer_typep(ct))
+						ret = ao_scheme_integer_poly(-ao_scheme_poly_integer(ret));
+					else if (ct == AO_SCHEME_FLOAT)
+						ret = ao_scheme_float_get(-ao_scheme_poly_number(ret));
+					break;
+				case builtin_divide:
+					if (ao_scheme_integer_typep(ct) && ao_scheme_poly_integer(ret) == 1)
+						;
+					else if (ao_scheme_number_typep(ct)) {
+						float	v = ao_scheme_poly_number(ret);
+						ret = ao_scheme_float_get(1/v);
+					}
+					break;
+				default:
+					break;
+				}
+			}
+		} else if (ao_scheme_integer_typep(rt) && ao_scheme_integer_typep(ct)) {
+			int32_t	r = ao_scheme_poly_integer(ret);
+			int32_t	c = ao_scheme_poly_integer(car);
+			int64_t t;
+
+			switch(op) {
+			case builtin_plus:
+				r += c;
+			check_overflow:
+				if (r < AO_SCHEME_MIN_BIGINT || AO_SCHEME_MAX_BIGINT < r)
+					goto inexact;
+				break;
+			case builtin_minus:
+				r -= c;
+				goto check_overflow;
+				break;
+			case builtin_times:
+				t = (int64_t) r * (int64_t) c;
+				if (t < AO_SCHEME_MIN_BIGINT || AO_SCHEME_MAX_BIGINT < t)
+					goto inexact;
+				r = (int32_t) t;
+				break;
+			case builtin_divide:
+				if (c != 0 && (r % c) == 0)
+					r /= c;
+				else
+					goto inexact;
+				break;
+			case builtin_quotient:
+				if (c == 0)
+					return ao_scheme_error(AO_SCHEME_DIVIDE_BY_ZERO, "quotient by zero");
+				if (r % c != 0 && (c < 0) != (r < 0))
+					r = r / c - 1;
+				else
+					r = r / c;
+				break;
+			case builtin_remainder:
+				if (c == 0)
+					return ao_scheme_error(AO_SCHEME_DIVIDE_BY_ZERO, "remainder by zero");
+				r %= c;
+				break;
+			case builtin_modulo:
+				if (c == 0)
+					return ao_scheme_error(AO_SCHEME_DIVIDE_BY_ZERO, "modulo by zero");
+				r %= c;
+				if ((r < 0) != (c < 0))
+					r += c;
+				break;
+			default:
+				break;
+			}
+			ret = ao_scheme_integer_poly(r);
+		} else if (ao_scheme_number_typep(rt) && ao_scheme_number_typep(ct)) {
+			float r, c;
+		inexact:
+			r = ao_scheme_poly_number(ret);
+			c = ao_scheme_poly_number(car);
+			switch(op) {
+			case builtin_plus:
+				r += c;
+				break;
+			case builtin_minus:
+				r -= c;
+				break;
+			case builtin_times:
+				r *= c;
+				break;
+			case builtin_divide:
+				r /= c;
+				break;
+			case builtin_quotient:
+			case builtin_remainder:
+			case builtin_modulo:
+				return ao_scheme_error(AO_SCHEME_INVALID, "non-integer value in integer divide");
+			default:
+				break;
+			}
+			ret = ao_scheme_float_get(r);
+		}
+
+		else if (rt == AO_SCHEME_STRING && ct == AO_SCHEME_STRING && op == builtin_plus)
+			ret = ao_scheme_string_poly(ao_scheme_string_cat(ao_scheme_poly_string(ret),
+								     ao_scheme_poly_string(car)));
+		else
+			return ao_scheme_error(AO_SCHEME_INVALID, "invalid args");
+	}
+	return ret;
+}
+
+ao_poly
+ao_scheme_do_plus(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_plus);
+}
+
+ao_poly
+ao_scheme_do_minus(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_minus);
+}
+
+ao_poly
+ao_scheme_do_times(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_times);
+}
+
+ao_poly
+ao_scheme_do_divide(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_divide);
+}
+
+ao_poly
+ao_scheme_do_quotient(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_quotient);
+}
+
+ao_poly
+ao_scheme_do_modulo(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_modulo);
+}
+
+ao_poly
+ao_scheme_do_remainder(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_math(cons, builtin_remainder);
+}
+
+ao_poly
+ao_scheme_compare(struct ao_scheme_cons *cons, enum ao_scheme_builtin_id op)
+{
+	ao_poly	left;
+
+	if (!cons)
+		return _ao_scheme_bool_true;
+
+	left = cons->car;
+	for (cons = ao_scheme_cons_cdr(cons); cons; cons = ao_scheme_cons_cdr(cons)) {
+		ao_poly	right = cons->car;
+
+		if (op == builtin_equal) {
+			if (left != right)
+				return _ao_scheme_bool_false;
+		} else {
+			uint8_t	lt = ao_scheme_poly_type(left);
+			uint8_t	rt = ao_scheme_poly_type(right);
+			if (ao_scheme_integer_typep(lt) && ao_scheme_integer_typep(rt)) {
+				int32_t l = ao_scheme_poly_integer(left);
+				int32_t r = ao_scheme_poly_integer(right);
+
+				switch (op) {
+				case builtin_less:
+					if (!(l < r))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_greater:
+					if (!(l > r))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_less_equal:
+					if (!(l <= r))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_greater_equal:
+					if (!(l >= r))
+						return _ao_scheme_bool_false;
+					break;
+				default:
+					break;
+				}
+			} else if (lt == AO_SCHEME_STRING && rt == AO_SCHEME_STRING) {
+				int c = strcmp(ao_scheme_poly_string(left),
+					       ao_scheme_poly_string(right));
+				switch (op) {
+				case builtin_less:
+					if (!(c < 0))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_greater:
+					if (!(c > 0))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_less_equal:
+					if (!(c <= 0))
+						return _ao_scheme_bool_false;
+					break;
+				case builtin_greater_equal:
+					if (!(c >= 0))
+						return _ao_scheme_bool_false;
+					break;
+				default:
+					break;
+				}
+			}
+		}
+		left = right;
+	}
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_equal(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_compare(cons, builtin_equal);
+}
+
+ao_poly
+ao_scheme_do_less(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_compare(cons, builtin_less);
+}
+
+ao_poly
+ao_scheme_do_greater(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_compare(cons, builtin_greater);
+}
+
+ao_poly
+ao_scheme_do_less_equal(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_compare(cons, builtin_less_equal);
+}
+
+ao_poly
+ao_scheme_do_greater_equal(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_compare(cons, builtin_greater_equal);
+}
+
+ao_poly
+ao_scheme_do_list_to_string(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_list2d3estring, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_list2d3estring, cons, 0, AO_SCHEME_CONS, 1))
+		return AO_SCHEME_NIL;
+	return ao_scheme_string_pack(ao_scheme_poly_cons(ao_scheme_arg(cons, 0)));
+}
+
+ao_poly
+ao_scheme_do_string_to_list(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_string2d3elist, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_string2d3elist, cons, 0, AO_SCHEME_STRING, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_string_unpack(ao_scheme_poly_string(ao_scheme_arg(cons, 0)));
+}
+
+ao_poly
+ao_scheme_do_flush_output(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_flush2doutput, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	ao_scheme_os_flush();
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_led(struct ao_scheme_cons *cons)
+{
+	ao_poly led;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_INT, 0))
+		return AO_SCHEME_NIL;
+	led = ao_scheme_arg(cons, 0);
+	ao_scheme_os_led(ao_scheme_poly_int(led));
+	return led;
+}
+
+ao_poly
+ao_scheme_do_delay(struct ao_scheme_cons *cons)
+{
+	ao_poly delay;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_INT, 0))
+		return AO_SCHEME_NIL;
+	delay = ao_scheme_arg(cons, 0);
+	ao_scheme_os_delay(ao_scheme_poly_int(delay));
+	return delay;
+}
+
+ao_poly
+ao_scheme_do_eval(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_eval, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	ao_scheme_stack->state = eval_sexpr;
+	return cons->car;
+}
+
+ao_poly
+ao_scheme_do_apply(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_apply, cons, 2, INT_MAX))
+		return AO_SCHEME_NIL;
+	ao_scheme_stack->state = eval_apply;
+	return ao_scheme_cons_poly(cons);
+}
+
+ao_poly
+ao_scheme_do_read(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_read, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_read();
+}
+
+ao_poly
+ao_scheme_do_collect(struct ao_scheme_cons *cons)
+{
+	int	free;
+	(void) cons;
+	free = ao_scheme_collect(AO_SCHEME_COLLECT_FULL);
+	return ao_scheme_int_poly(free);
+}
+
+ao_poly
+ao_scheme_do_nullp(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (ao_scheme_arg(cons, 0) == AO_SCHEME_NIL)
+		return _ao_scheme_bool_true;
+	else
+		return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_not(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (ao_scheme_arg(cons, 0) == _ao_scheme_bool_false)
+		return _ao_scheme_bool_true;
+	else
+		return _ao_scheme_bool_false;
+}
+
+static ao_poly
+ao_scheme_do_typep(int type, struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (ao_scheme_poly_type(ao_scheme_arg(cons, 0)) == type)
+		return _ao_scheme_bool_true;
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_pairp(struct ao_scheme_cons *cons)
+{
+	ao_poly	v;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	v = ao_scheme_arg(cons, 0);
+	if (v != AO_SCHEME_NIL && ao_scheme_poly_type(v) == AO_SCHEME_CONS)
+		return _ao_scheme_bool_true;
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_integerp(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	switch (ao_scheme_poly_type(ao_scheme_arg(cons, 0))) {
+	case AO_SCHEME_INT:
+	case AO_SCHEME_BIGINT:
+		return _ao_scheme_bool_true;
+	default:
+		return _ao_scheme_bool_false;
+	}
+}
+
+ao_poly
+ao_scheme_do_numberp(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	switch (ao_scheme_poly_type(ao_scheme_arg(cons, 0))) {
+	case AO_SCHEME_INT:
+	case AO_SCHEME_BIGINT:
+	case AO_SCHEME_FLOAT:
+		return _ao_scheme_bool_true;
+	default:
+		return _ao_scheme_bool_false;
+	}
+}
+
+ao_poly
+ao_scheme_do_stringp(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_do_typep(AO_SCHEME_STRING, cons);
+}
+
+ao_poly
+ao_scheme_do_symbolp(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_do_typep(AO_SCHEME_ATOM, cons);
+}
+
+ao_poly
+ao_scheme_do_booleanp(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_do_typep(AO_SCHEME_BOOL, cons);
+}
+
+ao_poly
+ao_scheme_do_procedurep(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	switch (ao_scheme_poly_type(ao_scheme_arg(cons, 0))) {
+	case AO_SCHEME_BUILTIN:
+	case AO_SCHEME_LAMBDA:
+		return _ao_scheme_bool_true;
+	default:
+	return _ao_scheme_bool_false;
+	}
+}
+
+/* This one is special -- a list is either nil or
+ * a 'proper' list with only cons cells
+ */
+ao_poly
+ao_scheme_do_listp(struct ao_scheme_cons *cons)
+{
+	ao_poly	v;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	v = ao_scheme_arg(cons, 0);
+	for (;;) {
+		if (v == AO_SCHEME_NIL)
+			return _ao_scheme_bool_true;
+		if (ao_scheme_poly_type(v) != AO_SCHEME_CONS)
+			return _ao_scheme_bool_false;
+		v = ao_scheme_poly_cons(v)->cdr;
+	}
+}
+
+ao_poly
+ao_scheme_do_set_car(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_CONS, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_poly_cons(ao_scheme_arg(cons, 0))->car = ao_scheme_arg(cons, 1);
+}
+
+ao_poly
+ao_scheme_do_set_cdr(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 2, 2))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_CONS, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_poly_cons(ao_scheme_arg(cons, 0))->cdr = ao_scheme_arg(cons, 1);
+}
+
+ao_poly
+ao_scheme_do_symbol_to_string(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_ATOM, 0))
+		return AO_SCHEME_NIL;
+	return ao_scheme_string_poly(ao_scheme_string_copy(ao_scheme_poly_atom(ao_scheme_arg(cons, 0))->name));
+}
+
+ao_poly
+ao_scheme_do_string_to_symbol(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_STRING, 0))
+		return AO_SCHEME_NIL;
+
+	return ao_scheme_atom_poly(ao_scheme_atom_intern(ao_scheme_poly_string(ao_scheme_arg(cons, 0))));
+}
+
+ao_poly
+ao_scheme_do_read_char(struct ao_scheme_cons *cons)
+{
+	int	c;
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	c = getchar();
+	return ao_scheme_int_poly(c);
+}
+
+ao_poly
+ao_scheme_do_write_char(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_led, cons, 0, AO_SCHEME_INT, 0))
+		return AO_SCHEME_NIL;
+	putchar(ao_scheme_poly_integer(ao_scheme_arg(cons, 0)));
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_exit(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	ao_scheme_exception |= AO_SCHEME_EXIT;
+	return _ao_scheme_bool_true;
+}
+
+ao_poly
+ao_scheme_do_current_jiffy(struct ao_scheme_cons *cons)
+{
+	int	jiffy;
+
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	jiffy = ao_scheme_os_jiffy();
+	return (ao_scheme_int_poly(jiffy));
+}
+
+ao_poly
+ao_scheme_do_current_second(struct ao_scheme_cons *cons)
+{
+	int	second;
+
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	second = ao_scheme_os_jiffy() / AO_SCHEME_JIFFIES_PER_SECOND;
+	return (ao_scheme_int_poly(second));
+}
+
+ao_poly
+ao_scheme_do_jiffies_per_second(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 0, 0))
+		return AO_SCHEME_NIL;
+	return (ao_scheme_int_poly(AO_SCHEME_JIFFIES_PER_SECOND));
+}
+
+#define AO_SCHEME_BUILTIN_FUNCS
+#include "ao_scheme_builtin.h"
diff --git a/src/scheme/ao_scheme_builtin.txt b/src/scheme/ao_scheme_builtin.txt
new file mode 100644
index 00000000..cb65e252
--- /dev/null
+++ b/src/scheme/ao_scheme_builtin.txt
@@ -0,0 +1,68 @@
+f_lambda	eval
+f_lambda	read
+nlambda		lambda
+nlambda		nlambda
+nlambda		macro
+f_lambda	car
+f_lambda	cdr
+f_lambda	cons
+f_lambda	last
+f_lambda	length
+nlambda		quote
+atom		quasiquote
+atom		unquote
+atom		unquote_splicing	unquote-splicing
+f_lambda	set
+macro		setq		set!
+f_lambda	def
+nlambda		cond
+nlambda		begin
+nlambda		while
+f_lambda	write
+f_lambda	display
+f_lambda	plus		+
+f_lambda	minus		-
+f_lambda	times		*
+f_lambda	divide		/
+f_lambda	modulo		modulo	%
+f_lambda	remainder
+f_lambda	quotient
+f_lambda	equal		=	eq?	eqv?
+f_lambda	less		<
+f_lambda	greater		>
+f_lambda	less_equal	<=
+f_lambda	greater_equal	>=
+f_lambda	list_to_string		list->string
+f_lambda	string_to_list		string->list
+f_lambda	flush_output		flush-output
+f_lambda	delay
+f_lambda	led
+f_lambda	save
+f_lambda	restore
+f_lambda	call_cc		call-with-current-continuation	call/cc
+f_lambda	collect
+f_lambda	nullp		null?
+f_lambda	not
+f_lambda	listp		list?
+f_lambda	pairp		pair?
+f_lambda	integerp	integer? exact? exact-integer?
+f_lambda	numberp		number? real?
+f_lambda	booleanp	boolean?
+f_lambda	set_car		set-car!
+f_lambda	set_cdr		set-cdr!
+f_lambda	symbolp		symbol?
+f_lambda	symbol_to_string	symbol->string
+f_lambda	string_to_symbol	string->symbol
+f_lambda	stringp		string?
+f_lambda	procedurep	procedure?
+lambda		apply
+f_lambda	read_char	read-char
+f_lambda	write_char	write-char
+f_lambda	exit
+f_lambda	current_jiffy	current-jiffy
+f_lambda	current_second	current-second
+f_lambda	jiffies_per_second	jiffies-per-second
+f_lambda	finitep		finite?
+f_lambda	infinitep	infinite?
+f_lambda	inexactp	inexact?
+f_lambda	sqrt
diff --git a/src/scheme/ao_scheme_cons.c b/src/scheme/ao_scheme_cons.c
new file mode 100644
index 00000000..03dad956
--- /dev/null
+++ b/src/scheme/ao_scheme_cons.c
@@ -0,0 +1,201 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+static void cons_mark(void *addr)
+{
+	struct ao_scheme_cons	*cons = addr;
+
+	for (;;) {
+		ao_poly cdr = cons->cdr;
+
+		ao_scheme_poly_mark(cons->car, 1);
+		if (!cdr)
+			break;
+		if (ao_scheme_poly_type(cdr) != AO_SCHEME_CONS) {
+			ao_scheme_poly_mark(cdr, 1);
+			break;
+		}
+		cons = ao_scheme_poly_cons(cdr);
+		if (ao_scheme_mark_memory(&ao_scheme_cons_type, cons))
+			break;
+	}
+}
+
+static int cons_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_cons);
+}
+
+static void cons_move(void *addr)
+{
+	struct ao_scheme_cons	*cons = addr;
+
+	if (!cons)
+		return;
+
+	for (;;) {
+		ao_poly			cdr;
+		struct ao_scheme_cons	*c;
+		int	ret;
+
+		MDBG_MOVE("cons_move start %d (%d, %d)\n",
+			  MDBG_OFFSET(cons), MDBG_OFFSET(ao_scheme_ref(cons->car)), MDBG_OFFSET(ao_scheme_ref(cons->cdr)));
+		(void) ao_scheme_poly_move(&cons->car, 1);
+		cdr = cons->cdr;
+		if (!cdr)
+			break;
+		if (ao_scheme_poly_base_type(cdr) != AO_SCHEME_CONS) {
+			(void) ao_scheme_poly_move(&cons->cdr, 0);
+			break;
+		}
+		c = ao_scheme_poly_cons(cdr);
+		ret = ao_scheme_move_memory(&ao_scheme_cons_type, (void **) &c);
+		if (c != ao_scheme_poly_cons(cons->cdr))
+			cons->cdr = ao_scheme_cons_poly(c);
+		MDBG_MOVE("cons_move end %d (%d, %d)\n",
+			  MDBG_OFFSET(cons), MDBG_OFFSET(ao_scheme_ref(cons->car)), MDBG_OFFSET(ao_scheme_ref(cons->cdr)));
+		if (ret)
+			break;
+		cons = c;
+	}
+}
+
+const struct ao_scheme_type ao_scheme_cons_type = {
+	.mark = cons_mark,
+	.size = cons_size,
+	.move = cons_move,
+	.name = "cons",
+};
+
+struct ao_scheme_cons *ao_scheme_cons_free_list;
+
+struct ao_scheme_cons *
+ao_scheme_cons_cons(ao_poly car, ao_poly cdr)
+{
+	struct ao_scheme_cons	*cons;
+
+	if (ao_scheme_cons_free_list) {
+		cons = ao_scheme_cons_free_list;
+		ao_scheme_cons_free_list = ao_scheme_poly_cons(cons->cdr);
+	} else {
+		ao_scheme_poly_stash(0, car);
+		ao_scheme_poly_stash(1, cdr);
+		cons = ao_scheme_alloc(sizeof (struct ao_scheme_cons));
+		cdr = ao_scheme_poly_fetch(1);
+		car = ao_scheme_poly_fetch(0);
+		if (!cons)
+			return NULL;
+	}
+	cons->car = car;
+	cons->cdr = cdr;
+	return cons;
+}
+
+struct ao_scheme_cons *
+ao_scheme_cons_cdr(struct ao_scheme_cons *cons)
+{
+	ao_poly	cdr = cons->cdr;
+	if (cdr == AO_SCHEME_NIL)
+		return NULL;
+	if (ao_scheme_poly_type(cdr) != AO_SCHEME_CONS) {
+		(void) ao_scheme_error(AO_SCHEME_INVALID, "improper list");
+		return NULL;
+	}
+	return ao_scheme_poly_cons(cdr);
+}
+
+ao_poly
+ao_scheme__cons(ao_poly car, ao_poly cdr)
+{
+	return ao_scheme_cons_poly(ao_scheme_cons_cons(car, cdr));
+}
+
+void
+ao_scheme_cons_free(struct ao_scheme_cons *cons)
+{
+#if DBG_FREE_CONS
+	ao_scheme_cons_check(cons);
+#endif
+	while (cons) {
+		ao_poly cdr = cons->cdr;
+		cons->cdr = ao_scheme_cons_poly(ao_scheme_cons_free_list);
+		ao_scheme_cons_free_list = cons;
+		cons = ao_scheme_poly_cons(cdr);
+	}
+}
+
+void
+ao_scheme_cons_write(ao_poly c)
+{
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(c);
+	ao_poly			cdr;
+	int			first = 1;
+
+	printf("(");
+	while (cons) {
+		if (!first)
+			printf(" ");
+		ao_scheme_poly_write(cons->car);
+		cdr = cons->cdr;
+		if (cdr == c) {
+			printf(" ...");
+			break;
+		}
+		if (ao_scheme_poly_type(cdr) == AO_SCHEME_CONS) {
+			cons = ao_scheme_poly_cons(cdr);
+			first = 0;
+		} else {
+			printf(" . ");
+			ao_scheme_poly_write(cdr);
+			cons = NULL;
+		}
+	}
+	printf(")");
+}
+
+void
+ao_scheme_cons_display(ao_poly c)
+{
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(c);
+	ao_poly			cdr;
+
+	while (cons) {
+		ao_scheme_poly_display(cons->car);
+		cdr = cons->cdr;
+		if (cdr == c) {
+			printf("...");
+			break;
+		}
+		if (ao_scheme_poly_type(cdr) == AO_SCHEME_CONS)
+			cons = ao_scheme_poly_cons(cdr);
+		else {
+			ao_scheme_poly_display(cdr);
+			cons = NULL;
+		}
+	}
+}
+
+int
+ao_scheme_cons_length(struct ao_scheme_cons *cons)
+{
+	int	len = 0;
+	while (cons) {
+		len++;
+		cons = ao_scheme_poly_cons(cons->cdr);
+	}
+	return len;
+}
diff --git a/src/scheme/ao_scheme_const.lisp b/src/scheme/ao_scheme_const.lisp
new file mode 100644
index 00000000..422bdd63
--- /dev/null
+++ b/src/scheme/ao_scheme_const.lisp
@@ -0,0 +1,813 @@
+;
+; Copyright © 2016 Keith Packard <keithp@keithp.com>
+;
+; This program is free software; you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, either version 2 of the License, or
+; (at your option) any later version.
+;
+; This program is distributed in the hope that it will be useful, but
+; WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+; General Public License for more details.
+;
+; Lisp code placed in ROM
+
+					; return a list containing all of the arguments
+(def (quote list) (lambda l l))
+
+(def (quote def!)
+     (macro (name value)
+	    (list
+	     def
+	     (list quote name)
+	     value)
+	    )
+     )
+
+(begin
+ (def! append
+   (lambda args
+	  (def! append-list
+	    (lambda (a b)
+	      (cond ((null? a) b)
+		    (else (cons (car a) (append-list (cdr a) b)))
+		    )
+	      )
+	    )
+	    
+	  (def! append-lists
+	    (lambda (lists)
+	      (cond ((null? lists) lists)
+		    ((null? (cdr lists)) (car lists))
+		    (else (append-list (car lists) (append-lists (cdr lists))))
+		    )
+	      )
+	    )
+	  (append-lists args)
+	  )
+   )
+ 'append)
+
+(append '(a b c) '(d e f) '(g h i))
+
+					; boolean operators
+
+(begin
+ (def! or
+   (macro l
+	  (def! _or
+	    (lambda (l)
+	      (cond ((null? l) #f)
+		    ((null? (cdr l))
+		     (car l))
+		    (else
+		     (list
+		      cond
+		      (list
+		       (car l))
+		      (list
+		       'else
+		       (_or (cdr l))
+		       )
+		      )
+		     )
+		    )
+	      )
+	    )
+	  (_or l)))
+ 'or)
+
+					; execute to resolve macros
+
+(or #f #t)
+
+(begin
+ (def! and
+   (macro l
+	  (def! _and
+	    (lambda (l)
+	      (cond ((null? l) #t)
+		    ((null? (cdr l))
+		     (car l))
+		    (else
+		     (list
+		      cond
+		      (list
+		       (car l)
+		       (_and (cdr l))
+		       )
+		      )
+		     )
+		    )
+	      )
+	    )
+	  (_and l)
+	  )
+   )
+ 'and)
+
+					; execute to resolve macros
+
+(and #t #f)
+
+(begin
+ (def! quasiquote
+   (macro (x)
+	  (def! constant?
+					; A constant value is either a pair starting with quote,
+					; or anything which is neither a pair nor a symbol
+
+	    (lambda (exp)
+	      (cond ((pair? exp)
+		     (eq? (car exp) 'quote)
+		     )
+		    (else
+		     (not (symbol? exp))
+		     )
+		    )
+	      )
+	    )
+	  (def! combine-skeletons
+	    (lambda (left right exp)
+	      (cond
+	       ((and (constant? left) (constant? right)) 
+		(cond ((and (eqv? (eval left) (car exp))
+			    (eqv? (eval right) (cdr exp)))
+		       (list 'quote exp)
+		       )
+		      (else
+		       (list 'quote (cons (eval left) (eval right)))
+		       )
+		      )
+		)
+	       ((null? right)
+		(list 'list left)
+		)
+	       ((and (pair? right) (eq? (car right) 'list))
+		(cons 'list (cons left (cdr right)))
+		)
+	       (else
+		(list 'cons left right)
+		)
+	       )
+	      )
+	    )
+
+	  (def! expand-quasiquote
+	    (lambda (exp nesting)
+	      (cond
+
+					; non cons -- constants
+					; themselves, others are
+					; quoted
+
+	       ((not (pair? exp)) 
+		(cond ((constant? exp)
+		       exp
+		       )
+		      (else
+		       (list 'quote exp)
+		       )
+		      )
+		)
+
+					; check for an unquote exp and
+					; add the param unquoted
+
+	       ((and (eq? (car exp) 'unquote) (= (length exp) 2))
+		(cond ((= nesting 0)
+		       (car (cdr exp))
+		       )
+		      (else
+		       (combine-skeletons ''unquote 
+					  (expand-quasiquote (cdr exp) (- nesting 1))
+					  exp))
+		      )
+		)
+
+					; nested quasi-quote --
+					; construct the right
+					; expression
+
+	       ((and (eq? (car exp) 'quasiquote) (= (length exp) 2))
+		(combine-skeletons ''quasiquote 
+				   (expand-quasiquote (cdr exp) (+ nesting 1))
+				   exp))
+
+					; check for an
+					; unquote-splicing member,
+					; compute the expansion of the
+					; value and append the rest of
+					; the quasiquote result to it
+
+	       ((and (pair? (car exp))
+		     (eq? (car (car exp)) 'unquote-splicing)
+		     (= (length (car exp)) 2))
+		(cond ((= nesting 0)
+		       (list 'append (car (cdr (car exp)))
+			     (expand-quasiquote (cdr exp) nesting))
+		       )
+		      (else
+		       (combine-skeletons (expand-quasiquote (car exp) (- nesting 1))
+					  (expand-quasiquote (cdr exp) nesting)
+					  exp))
+		      )
+		)
+
+					; for other lists, just glue
+					; the expansion of the first
+					; element to the expansion of
+					; the rest of the list
+
+	       (else (combine-skeletons (expand-quasiquote (car exp) nesting)
+					(expand-quasiquote (cdr exp) nesting)
+					exp)
+		     )
+	       )
+	      )
+	    )
+	  (def! result (expand-quasiquote x 0))
+	  result
+	  )
+   )
+ 'quasiquote)
+
+					;
+					; Define a variable without returning the value
+					; Useful when defining functions to avoid
+					; having lots of output generated.
+					;
+					; Also accepts the alternate
+					; form for defining lambdas of
+					; (define (name x y z) sexprs ...) 
+					;
+
+(begin
+ (def! define
+   (macro (first . rest)
+					; check for alternate lambda definition form
+
+	  (cond ((list? first)
+		 (set! rest
+		       (append
+			(list
+			 'lambda
+			 (cdr first))
+			rest))
+		 (set! first (car first))
+		 )
+		(else
+		 (set! rest (car rest))
+		 )
+		)
+	  (def! result `(,begin
+			 (,def (,quote ,first) ,rest)
+			 (,quote ,first))
+	    )
+	  result
+	  )
+   )
+ 'define
+ )
+
+					; basic list accessors
+
+(define (caar l) (car (car l)))
+
+(define (cadr l) (car (cdr l)))
+
+(define (cdar l) (cdr (car l)))
+
+(define (caddr l) (car (cdr (cdr l))))
+
+					; (if <condition> <if-true>)
+					; (if <condition> <if-true> <if-false)
+
+(define if
+  (macro (test . args)
+	 (cond ((null? (cdr args))
+		`(cond (,test ,(car args)))
+		)
+	       (else
+		`(cond (,test ,(car args))
+		       (else ,(cadr args)))
+		)
+	       )
+	 )
+  )
+
+(if (> 3 2) 'yes)
+(if (> 3 2) 'yes 'no)
+(if (> 2 3) 'no 'yes)
+(if (> 2 3) 'no)
+
+					; simple math operators
+
+(define zero? (macro (value) `(eq? ,value 0)))
+
+(zero? 1)
+(zero? 0)
+(zero? "hello")
+
+(define positive? (macro (value) `(> ,value 0)))
+
+(positive? 12)
+(positive? -12)
+
+(define negative? (macro (value) `(< ,value 0)))
+
+(negative? 12)
+(negative? -12)
+
+(define (abs x) (if (>= x 0) x (- x)))
+
+(abs 12)
+(abs -12)
+
+(define max (lambda (first . rest)
+		   (while (not (null? rest))
+		     (cond ((< first (car rest))
+			    (set! first (car rest)))
+			   )
+		     (set! rest (cdr rest))
+		     )
+		   first)
+  )
+
+(max 1 2 3)
+(max 3 2 1)
+
+(define min (lambda (first . rest)
+		   (while (not (null? rest))
+		     (cond ((> first (car rest))
+			    (set! first (car rest)))
+			   )
+		     (set! rest (cdr rest))
+		     )
+		   first)
+  )
+
+(min 1 2 3)
+(min 3 2 1)
+
+(define (even? x) (zero? (% x 2)))
+
+(even? 2)
+(even? -2)
+(even? 3)
+(even? -1)
+
+(define (odd? x) (not (even? x)))
+
+(odd? 2)
+(odd? -2)
+(odd? 3)
+(odd? -1)
+
+
+(define (list-tail x k)
+  (if (zero? k)
+      x
+    (list-tail (cdr x (- k 1)))
+    )
+  )
+
+(define (list-ref x k)
+  (car (list-tail x k))
+  )
+
+					; define a set of local
+					; variables all at once and
+					; then evaluate a list of
+					; sexprs
+					;
+					; (let (var-defines) sexprs)
+					;
+					; where var-defines are either
+					;
+					; (name value)
+					;
+					; or
+					;
+					; (name)
+					;
+					; e.g.
+					;
+					; (let ((x 1) (y)) (set! y (+ x 1)) y)
+
+(define let
+  (macro (vars . exprs)
+	 (define (make-names vars)
+	   (cond ((not (null? vars))
+		  (cons (car (car vars))
+			(make-names (cdr vars))))
+		 (else ())
+		 )
+	   )
+
+					; the parameters to the lambda is a list
+					; of nils of the right length
+
+	 (define (make-vals vars)
+	   (cond ((not (null? vars))
+		  (cons (cond ((null? (cdr (car vars))) ())
+			      (else
+			       (car (cdr (car vars))))
+			      )
+			(make-vals (cdr vars))))
+		 (else ())
+		 )
+	   )
+					; prepend the set operations
+					; to the expressions
+
+					; build the lambda.
+
+	 `((lambda ,(make-names vars) ,@exprs) ,@(make-vals vars))
+	 )
+     )
+		   
+
+(let ((x 1) (y)) (set! y 2) (+ x y))
+
+					; define a set of local
+					; variables one at a time and
+					; then evaluate a list of
+					; sexprs
+					;
+					; (let* (var-defines) sexprs)
+					;
+					; where var-defines are either
+					;
+					; (name value)
+					;
+					; or
+					;
+					; (name)
+					;
+					; e.g.
+					;
+					; (let* ((x 1) (y)) (set! y (+ x 1)) y)
+
+(define let*
+  (macro (vars . exprs)
+
+					;
+					; make the list of names in the let
+					;
+
+	 (define (make-names vars)
+	   (cond ((not (null? vars))
+		  (cons (car (car vars))
+			(make-names (cdr vars))))
+		 (else ())
+		 )
+	   )
+
+					; the set of expressions is
+					; the list of set expressions
+					; pre-pended to the
+					; expressions to evaluate
+
+	 (define (make-exprs vars exprs)
+	   (cond ((null? vars) exprs)
+		 (else
+		  (cons
+		   (list set
+			 (list quote
+			       (car (car vars))
+			       )
+			 (cond ((null? (cdr (car vars))) ())
+			       (else (cadr (car vars))))
+			 )
+		   (make-exprs (cdr vars) exprs)
+		   )
+		  )
+		 )
+	   )
+
+					; the parameters to the lambda is a list
+					; of nils of the right length
+
+	 (define (make-nils vars)
+	   (cond ((null? vars) ())
+		 (else (cons () (make-nils (cdr vars))))
+		 )
+	   )
+					; build the lambda.
+
+	 `((lambda ,(make-names vars) ,@(make-exprs vars exprs)) ,@(make-nils vars))
+	 )
+     )
+
+(let* ((x 1) (y x)) (+ x y))
+
+(define when (macro (test . l) `(cond (,test ,@l))))
+
+(when #t (write 'when))
+
+(define unless (macro (test . l) `(cond ((not ,test) ,@l))))
+
+(unless #f (write 'unless))
+
+(define (reverse list)
+  (let ((result ()))
+    (while (not (null? list))
+      (set! result (cons (car list) result))
+      (set! list (cdr list))
+      )
+    result)
+  )
+
+(reverse '(1 2 3))
+
+(define (list-tail x k)
+  (if (zero? k)
+      x
+    (list-tail (cdr x) (- k 1))))
+
+(list-tail '(1 2 3) 2)
+
+(define (list-ref x k) (car (list-tail x k)))
+
+(list-ref '(1 2 3) 2)
+    
+					; recursive equality
+
+(define (equal? a b)
+  (cond ((eq? a b) #t)
+	((and (pair? a) (pair? b))
+	 (and (equal? (car a) (car b))
+	      (equal? (cdr a) (cdr b)))
+	 )
+	(else #f)
+	)
+  )
+
+(equal? '(a b c) '(a b c))
+(equal? '(a b c) '(a b b))
+
+(define member (lambda (obj list . test?)
+		      (cond ((null? list)
+			     #f
+			     )
+			    (else
+			     (if (null? test?) (set! test? equal?) (set! test? (car test?)))
+			     (if (test? obj (car list))
+				 list
+			       (member obj (cdr list) test?))
+			     )
+			    )
+		      )
+  )
+
+(member '(2) '((1) (2) (3)))
+
+(member '(4) '((1) (2) (3)))
+
+(define (memq obj list) (member obj list eq?))
+
+(memq 2 '(1 2 3))
+
+(memq 4 '(1 2 3))
+
+(memq '(2) '((1) (2) (3)))
+
+(define (memv obj list) (member obj list eqv?))
+
+(memv 2 '(1 2 3))
+
+(memv 4 '(1 2 3))
+
+(memv '(2) '((1) (2) (3)))
+
+(define (_assoc obj list test?)
+  (if (null? list)
+      #f
+    (if (test? obj (caar list))
+	(car list)
+      (_assoc obj (cdr list) test?)
+      )
+    )
+  )
+
+(define (assq obj list) (_assoc obj list eq?))
+(define (assv obj list) (_assoc obj list eqv?))
+(define (assoc obj list) (_assoc obj list equal?))
+
+(assq 'a '((a 1) (b 2) (c 3)))
+(assv 'b '((a 1) (b 2) (c 3)))
+(assoc '(c) '((a 1) (b 2) ((c) 3)))
+
+(define char? integer?)
+
+(char? #\q)
+(char? "h")
+
+(define (char-upper-case? c) (<= #\A c #\Z))
+
+(char-upper-case? #\a)
+(char-upper-case? #\B)
+(char-upper-case? #\0)
+(char-upper-case? #\space)
+
+(define (char-lower-case? c) (<= #\a c #\a))
+
+(char-lower-case? #\a)
+(char-lower-case? #\B)
+(char-lower-case? #\0)
+(char-lower-case? #\space)
+
+(define (char-alphabetic? c) (or (char-upper-case? c) (char-lower-case? c)))
+
+(char-alphabetic? #\a)
+(char-alphabetic? #\B)
+(char-alphabetic? #\0)
+(char-alphabetic? #\space)
+
+(define (char-numeric? c) (<= #\0 c #\9))
+
+(char-numeric? #\a)
+(char-numeric? #\B)
+(char-numeric? #\0)
+(char-numeric? #\space)
+
+(define (char-whitespace? c) (or (<= #\tab c #\return) (= #\space c)))
+
+(char-whitespace? #\a)
+(char-whitespace? #\B)
+(char-whitespace? #\0)
+(char-whitespace? #\space)
+
+(define (char->integer c) c)
+(define (integer->char c) char-integer)
+
+(define (char-upcase c) (if (char-lower-case? c) (+ c (- #\A #\a)) c))
+
+(char-upcase #\a)
+(char-upcase #\B)
+(char-upcase #\0)
+(char-upcase #\space)
+
+(define (char-downcase c) (if (char-upper-case? c) (+ c (- #\a #\A)) c))
+
+(char-downcase #\a)
+(char-downcase #\B)
+(char-downcase #\0)
+(char-downcase #\space)
+
+(define string (lambda chars (list->string chars)))
+
+(display "apply\n")
+(apply cons '(a b))
+
+(define map
+  (lambda (proc . lists)
+	 (define (args lists)
+	   (cond ((null? lists) ())
+		 (else
+		  (cons (caar lists) (args (cdr lists)))
+		  )
+		 )
+	   )
+	 (define (next lists)
+	   (cond ((null? lists) ())
+		 (else
+		  (cons (cdr (car lists)) (next (cdr lists)))
+		  )
+		 )
+	   )
+	 (define (domap lists)
+	   (cond ((null? (car lists)) ())
+		 (else
+		  (cons (apply proc (args lists)) (domap (next lists)))
+		  )
+		 )
+	   )
+	 (domap lists)
+	 )
+  )
+
+(map cadr '((a b) (d e) (g h)))
+
+(define for-each (lambda (proc . lists)
+			(apply map proc lists)
+			#t))
+
+(for-each display '("hello" " " "world" "\n"))
+
+(define (_string-ml strings)
+  (if (null? strings) ()
+    (cons (string->list (car strings)) (_string-ml (cdr strings)))
+    )
+  )
+
+(define string-map (lambda (proc . strings)
+			  (list->string (apply map proc (_string-ml strings))))))
+
+(string-map (lambda (x) (+ 1 x)) "HAL")
+
+(define string-for-each (lambda (proc . strings)
+			       (apply for-each proc (_string-ml strings))))
+
+(string-for-each write-char "IBM\n")
+
+(define (newline) (write-char #\newline))
+
+(newline)
+
+(call-with-current-continuation
+ (lambda (exit)
+   (for-each (lambda (x)
+	       (write "test" x)
+	       (if (negative? x)
+		   (exit x)))
+	     '(54 0 37 -3 245 19))
+   #t))
+
+
+					; `q -> (quote q)
+					; `(q) -> (append (quote (q)))
+					; `(a ,(+ 1 2)) -> (append (quote (a)) (list (+ 1 2)))
+					; `(a ,@(list 1 2 3) -> (append (quote (a)) (list 1 2 3))
+
+
+
+`(hello ,(+ 1 2) ,@(list 1 2 3) `foo)
+
+
+(define repeat
+  (macro (count . rest)
+	 (define counter '__count__)
+	 (cond ((pair? count)
+		(set! counter (car count))
+		(set! count (cadr count))
+		)
+	       )
+	 `(let ((,counter 0)
+		(__max__ ,count)
+		)
+	    (while (< ,counter __max__)
+	      ,@rest
+	      (set! ,counter (+ ,counter 1))
+	      )
+	    )
+	 )
+  )
+
+(repeat 2 (write 'hello))
+(repeat (x 3) (write 'goodbye x))
+
+(define case
+  (macro (test . l)
+					; construct the body of the
+					; case, dealing with the
+					; lambda version ( => lambda)
+
+	 (define (_unarrow l)
+	   (cond ((null? l) l)
+		 ((eq? (car l) '=>) `(( ,(cadr l) __key__)))
+		 (else l))
+	   )
+
+					; Build the case elements, which is
+					; simply a list of cond clauses
+
+	 (define (_case l)
+
+	   (cond ((null? l) ())
+
+					; else case
+
+		 ((eq? (caar l) 'else)
+		  `((else ,@(_unarrow (cdr (car l))))))
+
+					; regular case
+		 
+		 (else
+		  (cons
+		   `((eqv? ,(caar l) __key__)
+		     ,@(_unarrow (cdr (car l))))
+		   (_case (cdr l)))
+		  )
+		 )
+	   )
+
+					; now construct the overall
+					; expression, using a lambda
+					; to hold the computed value
+					; of the test expression
+
+	 `((lambda (__key__)
+	     (cond ,@(_case l))) ,test)
+	 )
+  )
+
+(case 12 (1 "one") (2 "two") (3 => (lambda (x) (write "the value is" x))) (12 "twelve") (else "else"))
+
+;(define number->string (lambda (arg . opt)
+;			      (let ((base (if (null? opt) 10 (car opt)))
+					;
+;
+				
diff --git a/src/scheme/ao_scheme_error.c b/src/scheme/ao_scheme_error.c
new file mode 100644
index 00000000..d580a2c0
--- /dev/null
+++ b/src/scheme/ao_scheme_error.c
@@ -0,0 +1,139 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <stdarg.h>
+
+void
+ao_scheme_error_poly(char *name, ao_poly poly, ao_poly last)
+{
+	int first = 1;
+	printf("\t\t%s(", name);
+	if (ao_scheme_poly_type(poly) == AO_SCHEME_CONS) {
+		if (poly) {
+			while (poly) {
+				struct ao_scheme_cons *cons = ao_scheme_poly_cons(poly);
+				if (!first)
+					printf("\t\t         ");
+				else
+					first = 0;
+				ao_scheme_poly_write(cons->car);
+				printf("\n");
+				if (poly == last)
+					break;
+				poly = cons->cdr;
+			}
+			printf("\t\t         )\n");
+		} else
+			printf(")\n");
+	} else {
+		ao_scheme_poly_write(poly);
+		printf("\n");
+	}
+}
+
+static void tabs(int indent)
+{
+	while (indent--)
+		printf("\t");
+}
+
+void
+ao_scheme_error_frame(int indent, char *name, struct ao_scheme_frame *frame)
+{
+	int			f;
+
+	tabs(indent);
+	printf ("%s{", name);
+	if (frame) {
+		struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(frame->vals);
+		if (frame->type & AO_SCHEME_FRAME_PRINT)
+			printf("recurse...");
+		else {
+			frame->type |= AO_SCHEME_FRAME_PRINT;
+			for (f = 0; f < frame->num; f++) {
+				if (f != 0) {
+					tabs(indent);
+					printf("         ");
+				}
+				ao_scheme_poly_write(vals->vals[f].atom);
+				printf(" = ");
+				ao_scheme_poly_write(vals->vals[f].val);
+				printf("\n");
+			}
+			if (frame->prev)
+				ao_scheme_error_frame(indent + 1, "prev:   ", ao_scheme_poly_frame(frame->prev));
+			frame->type &= ~AO_SCHEME_FRAME_PRINT;
+		}
+		tabs(indent);
+		printf("        }\n");
+	} else
+		printf ("}\n");
+}
+
+void
+ao_scheme_vprintf(char *format, va_list args)
+{
+	char c;
+
+	while ((c = *format++) != '\0') {
+		if (c == '%') {
+			switch (c = *format++) {
+			case 'v':
+				ao_scheme_poly_write((ao_poly) va_arg(args, unsigned int));
+				break;
+			case 'p':
+				printf("%p", va_arg(args, void *));
+				break;
+			case 'd':
+				printf("%d", va_arg(args, int));
+				break;
+			case 's':
+				printf("%s", va_arg(args, char *));
+				break;
+			default:
+				putchar(c);
+				break;
+			}
+		} else
+			putchar(c);
+	}
+}
+
+void
+ao_scheme_printf(char *format, ...)
+{
+	va_list args;
+	va_start(args, format);
+	ao_scheme_vprintf(format, args);
+	va_end(args);
+}
+
+ao_poly
+ao_scheme_error(int error, char *format, ...)
+{
+	va_list	args;
+
+	ao_scheme_exception |= error;
+	va_start(args, format);
+	ao_scheme_vprintf(format, args);
+	putchar('\n');
+	va_end(args);
+	ao_scheme_printf("Value:  %v\n", ao_scheme_v);
+	ao_scheme_printf("Frame:  %v\n", ao_scheme_frame_poly(ao_scheme_frame_current));
+	printf("Stack:\n");
+	ao_scheme_stack_write(ao_scheme_stack_poly(ao_scheme_stack));
+	ao_scheme_printf("Globals: %v\n", ao_scheme_frame_poly(ao_scheme_frame_global));
+	return AO_SCHEME_NIL;
+}
diff --git a/src/scheme/ao_scheme_eval.c b/src/scheme/ao_scheme_eval.c
new file mode 100644
index 00000000..9b3cf63e
--- /dev/null
+++ b/src/scheme/ao_scheme_eval.c
@@ -0,0 +1,578 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <assert.h>
+
+struct ao_scheme_stack		*ao_scheme_stack;
+ao_poly				ao_scheme_v;
+uint8_t				ao_scheme_skip_cons_free;
+
+ao_poly
+ao_scheme_set_cond(struct ao_scheme_cons *c)
+{
+	ao_scheme_stack->state = eval_cond;
+	ao_scheme_stack->sexprs = ao_scheme_cons_poly(c);
+	return AO_SCHEME_NIL;
+}
+
+static int
+func_type(ao_poly func)
+{
+	if (func == AO_SCHEME_NIL)
+		return ao_scheme_error(AO_SCHEME_INVALID, "func is nil");
+	switch (ao_scheme_poly_type(func)) {
+	case AO_SCHEME_BUILTIN:
+		return ao_scheme_poly_builtin(func)->args & AO_SCHEME_FUNC_MASK;
+	case AO_SCHEME_LAMBDA:
+		return ao_scheme_poly_lambda(func)->args;
+	case AO_SCHEME_STACK:
+		return AO_SCHEME_FUNC_LAMBDA;
+	default:
+		ao_scheme_error(AO_SCHEME_INVALID, "not a func");
+		return -1;
+	}
+}
+
+/*
+ * Flattened eval to avoid stack issues
+ */
+
+/*
+ * Evaluate an s-expression
+ *
+ * For a list, evaluate all of the elements and
+ * then execute the resulting function call.
+ *
+ * Each element of the list is evaluated in
+ * a clean stack context.
+ *
+ * The current stack state is set to 'formal' so that
+ * when the evaluation is complete, the value
+ * will get appended to the values list.
+ *
+ * For other types, compute the value directly.
+ */
+
+static int
+ao_scheme_eval_sexpr(void)
+{
+	DBGI("sexpr: %v\n", ao_scheme_v);
+	switch (ao_scheme_poly_type(ao_scheme_v)) {
+	case AO_SCHEME_CONS:
+		if (ao_scheme_v == AO_SCHEME_NIL) {
+			if (!ao_scheme_stack->values) {
+				/*
+				 * empty list evaluates to empty list
+				 */
+				ao_scheme_v = AO_SCHEME_NIL;
+				ao_scheme_stack->state = eval_val;
+			} else {
+				/*
+				 * done with arguments, go execute it
+				 */
+				ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
+				ao_scheme_stack->state = eval_exec;
+			}
+		} else {
+			if (!ao_scheme_stack->values)
+				ao_scheme_stack->list = ao_scheme_v;
+			/*
+			 * Evaluate another argument and then switch
+			 * to 'formal' to add the value to the values
+			 * list
+			 */
+			ao_scheme_stack->sexprs = ao_scheme_v;
+			ao_scheme_stack->state = eval_formal;
+			if (!ao_scheme_stack_push())
+				return 0;
+			/*
+			 * push will reset the state to 'sexpr', which
+			 * will evaluate the expression
+			 */
+			ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
+		}
+		break;
+	case AO_SCHEME_ATOM:
+		DBGI("..frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+		ao_scheme_v = ao_scheme_atom_get(ao_scheme_v);
+		/* fall through */
+	case AO_SCHEME_BOOL:
+	case AO_SCHEME_INT:
+	case AO_SCHEME_BIGINT:
+	case AO_SCHEME_FLOAT:
+	case AO_SCHEME_STRING:
+	case AO_SCHEME_BUILTIN:
+	case AO_SCHEME_LAMBDA:
+		ao_scheme_stack->state = eval_val;
+		break;
+	}
+	DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG("\n");
+	return 1;
+}
+
+/*
+ * A value has been computed.
+ *
+ * If the value was computed from a macro,
+ * then we want to reset the current context
+ * to evaluate the macro result again.
+ *
+ * If not a macro, then pop the stack.
+ * If the stack is empty, we're done.
+ * Otherwise, the stack will contain
+ * the next state.
+ */
+
+static int
+ao_scheme_eval_val(void)
+{
+	DBGI("val: "); DBG_POLY(ao_scheme_v); DBG("\n");
+	/*
+	 * Value computed, pop the stack
+	 * to figure out what to do with the value
+	 */
+	ao_scheme_stack_pop();
+	DBGI("..state %d\n", ao_scheme_stack ? ao_scheme_stack->state : -1);
+	return 1;
+}
+
+/*
+ * A formal has been computed.
+ *
+ * If this is the first formal, then check to see if we've got a
+ * lamda, macro or nlambda.
+ *
+ * For lambda, go compute another formal.  This will terminate
+ * when the sexpr state sees nil.
+ *
+ * For macro/nlambda, we're done, so move the sexprs into the values
+ * and go execute it.
+ *
+ * Macros have an additional step of saving a stack frame holding the
+ * macro value execution context, which then gets the result of the
+ * macro to run
+ */
+
+static int
+ao_scheme_eval_formal(void)
+{
+	ao_poly			formal;
+	struct ao_scheme_stack	*prev;
+
+	DBGI("formal: "); DBG_POLY(ao_scheme_v); DBG("\n");
+
+	/* Check what kind of function we've got */
+	if (!ao_scheme_stack->values) {
+		switch (func_type(ao_scheme_v)) {
+		case AO_SCHEME_FUNC_LAMBDA:
+			DBGI(".. lambda\n");
+			break;
+		case AO_SCHEME_FUNC_MACRO:
+			/* Evaluate the result once more */
+			ao_scheme_stack->state = eval_macro;
+			if (!ao_scheme_stack_push())
+				return 0;
+
+			/* After the function returns, take that
+			 * value and re-evaluate it
+			 */
+			prev = ao_scheme_poly_stack(ao_scheme_stack->prev);
+			ao_scheme_stack->sexprs = prev->sexprs;
+
+			DBGI(".. start macro\n");
+			DBGI("\t.. sexprs       "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+			DBGI("\t.. values       "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
+			DBG_FRAMES();
+
+			/* fall through ... */
+		case AO_SCHEME_FUNC_NLAMBDA:
+			DBGI(".. nlambda or macro\n");
+
+			/* use the raw sexprs as values */
+			ao_scheme_stack->values = ao_scheme_stack->sexprs;
+			ao_scheme_stack->values_tail = AO_SCHEME_NIL;
+			ao_scheme_stack->state = eval_exec;
+
+			/* ready to execute now */
+			return 1;
+		case -1:
+			return 0;
+		}
+	}
+
+	/* Append formal to list of values */
+	formal = ao_scheme__cons(ao_scheme_v, AO_SCHEME_NIL);
+	if (!formal)
+		return 0;
+
+	if (ao_scheme_stack->values_tail)
+		ao_scheme_poly_cons(ao_scheme_stack->values_tail)->cdr = formal;
+	else
+		ao_scheme_stack->values = formal;
+	ao_scheme_stack->values_tail = formal;
+
+	DBGI(".. values "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
+
+	/*
+	 * Step to the next argument, if this is last, then
+	 * 'sexpr' will end up switching to 'exec'
+	 */
+	ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
+
+	ao_scheme_stack->state = eval_sexpr;
+
+	DBGI(".. "); DBG_POLY(ao_scheme_v); DBG("\n");
+	return 1;
+}
+
+/*
+ * Start executing a function call
+ *
+ * Most builtins are easy, just call the function.
+ * 'cond' is magic; it sticks the list of clauses
+ * in 'sexprs' and switches to 'cond' state. That
+ * bit of magic is done in ao_scheme_set_cond.
+ *
+ * Lambdas build a new frame to hold the locals and
+ * then re-use the current stack context to evaluate
+ * the s-expression from the lambda.
+ */
+
+static int
+ao_scheme_eval_exec(void)
+{
+	ao_poly v;
+	struct ao_scheme_builtin	*builtin;
+
+	DBGI("exec: "); DBG_POLY(ao_scheme_v); DBG(" values "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
+	ao_scheme_stack->sexprs = AO_SCHEME_NIL;
+	switch (ao_scheme_poly_type(ao_scheme_v)) {
+	case AO_SCHEME_BUILTIN:
+		ao_scheme_stack->state = eval_val;
+		builtin = ao_scheme_poly_builtin(ao_scheme_v);
+		v = ao_scheme_func(builtin) (
+			ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->values)->cdr));
+		DBG_DO(if (!ao_scheme_exception && ao_scheme_poly_builtin(ao_scheme_v)->func == builtin_set) {
+				struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
+				ao_poly atom = ao_scheme_arg(cons, 1);
+				ao_poly val = ao_scheme_arg(cons, 2);
+				DBGI("set "); DBG_POLY(atom); DBG(" = "); DBG_POLY(val); DBG("\n");
+			});
+		builtin = ao_scheme_poly_builtin(ao_scheme_v);
+		if (builtin && (builtin->args & AO_SCHEME_FUNC_FREE_ARGS) && !ao_scheme_stack_marked(ao_scheme_stack) && !ao_scheme_skip_cons_free) {
+			struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
+			ao_scheme_stack->values = AO_SCHEME_NIL;
+			ao_scheme_cons_free(cons);
+		}
+
+		ao_scheme_v = v;
+		ao_scheme_stack->values = AO_SCHEME_NIL;
+		ao_scheme_stack->values_tail = AO_SCHEME_NIL;
+		DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG ("\n");
+		DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+		break;
+	case AO_SCHEME_LAMBDA:
+		DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+		ao_scheme_stack->state = eval_begin;
+		v = ao_scheme_lambda_eval();
+		ao_scheme_stack->sexprs = v;
+		ao_scheme_stack->values = AO_SCHEME_NIL;
+		ao_scheme_stack->values_tail = AO_SCHEME_NIL;
+		DBGI(".. sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+		DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+		break;
+	case AO_SCHEME_STACK:
+		DBGI(".. stack "); DBG_POLY(ao_scheme_v); DBG("\n");
+		ao_scheme_v = ao_scheme_stack_eval();
+		DBGI(".. value "); DBG_POLY(ao_scheme_v); DBG("\n");
+		DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+		break;
+	}
+	ao_scheme_skip_cons_free = 0;
+	return 1;
+}
+
+/*
+ * Finish setting up the apply evaluation
+ *
+ * The value is the list to execute
+ */
+static int
+ao_scheme_eval_apply(void)
+{
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(ao_scheme_v);
+	struct ao_scheme_cons	*cdr, *prev;
+
+	/* Glue the arguments into the right shape. That's all but the last
+	 * concatenated onto the last
+	 */
+	cdr = cons;
+	for (;;) {
+		prev = cdr;
+		cdr = ao_scheme_poly_cons(prev->cdr);
+		if (cdr->cdr == AO_SCHEME_NIL)
+			break;
+	}
+	DBGI("before mangling: "); DBG_POLY(ao_scheme_v); DBG("\n");
+	prev->cdr = cdr->car;
+	ao_scheme_stack->values = ao_scheme_v;
+	ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
+	DBGI("apply: "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
+	ao_scheme_stack->state = eval_exec;
+	ao_scheme_skip_cons_free = 1;
+	return 1;
+}
+
+/*
+ * Start evaluating the next cond clause
+ *
+ * If the list of clauses is empty, then
+ * the result of the cond is nil.
+ *
+ * Otherwise, set the current stack state to 'cond_test' and create a
+ * new stack context to evaluate the test s-expression. Once that's
+ * complete, we'll land in 'cond_test' to finish the clause.
+ */
+static int
+ao_scheme_eval_cond(void)
+{
+	DBGI("cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+	DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
+	if (!ao_scheme_stack->sexprs) {
+		ao_scheme_v = _ao_scheme_bool_false;
+		ao_scheme_stack->state = eval_val;
+	} else {
+		ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
+		if (!ao_scheme_v || ao_scheme_poly_type(ao_scheme_v) != AO_SCHEME_CONS) {
+			ao_scheme_error(AO_SCHEME_INVALID, "invalid cond clause");
+			return 0;
+		}
+		ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
+		if (ao_scheme_v == _ao_scheme_atom_else)
+			ao_scheme_v = _ao_scheme_bool_true;
+		ao_scheme_stack->state = eval_cond_test;
+		if (!ao_scheme_stack_push())
+			return 0;
+	}
+	return 1;
+}
+
+/*
+ * Finish a cond clause.
+ *
+ * Check the value from the test expression, if
+ * non-nil, then set up to evaluate the value expression.
+ *
+ * Otherwise, step to the next clause and go back to the 'cond'
+ * state
+ */
+static int
+ao_scheme_eval_cond_test(void)
+{
+	DBGI("cond_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+	DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
+	if (ao_scheme_v != _ao_scheme_bool_false) {
+		struct ao_scheme_cons *car = ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car);
+		ao_poly c = car->cdr;
+
+		if (c) {
+			ao_scheme_stack->state = eval_begin;
+			ao_scheme_stack->sexprs = c;
+		} else
+			ao_scheme_stack->state = eval_val;
+	} else {
+		ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
+		DBGI("next cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+		ao_scheme_stack->state = eval_cond;
+	}
+	return 1;
+}
+
+/*
+ * Evaluate a list of sexprs, returning the value from the last one.
+ *
+ * ao_scheme_begin records the list in stack->sexprs, so we just need to
+ * walk that list. Set ao_scheme_v to the car of the list and jump to
+ * eval_sexpr. When that's done, it will land in eval_val. For all but
+ * the last, leave a stack frame with eval_begin set so that we come
+ * back here. For the last, don't add a stack frame so that we can
+ * just continue on.
+ */
+static int
+ao_scheme_eval_begin(void)
+{
+	DBGI("begin: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+	DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
+
+	if (!ao_scheme_stack->sexprs) {
+		ao_scheme_v = AO_SCHEME_NIL;
+		ao_scheme_stack->state = eval_val;
+	} else {
+		ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
+		ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
+
+		/* If there are more sexprs to do, then come back here, otherwise
+		 * return the value of the last one by just landing in eval_sexpr
+		 */
+		if (ao_scheme_stack->sexprs) {
+			ao_scheme_stack->state = eval_begin;
+			if (!ao_scheme_stack_push())
+				return 0;
+		}
+		ao_scheme_stack->state = eval_sexpr;
+	}
+	return 1;
+}
+
+/*
+ * Conditionally execute a list of sexprs while the first is true
+ */
+static int
+ao_scheme_eval_while(void)
+{
+	DBGI("while: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+	DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
+
+	ao_scheme_stack->values = ao_scheme_v;
+	if (!ao_scheme_stack->sexprs) {
+		ao_scheme_v = AO_SCHEME_NIL;
+		ao_scheme_stack->state = eval_val;
+	} else {
+		ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
+		ao_scheme_stack->state = eval_while_test;
+		if (!ao_scheme_stack_push())
+			return 0;
+	}
+	return 1;
+}
+
+/*
+ * Check the while condition, terminate the loop if nil. Otherwise keep going
+ */
+static int
+ao_scheme_eval_while_test(void)
+{
+	DBGI("while_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+	DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
+	DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
+
+	if (ao_scheme_v != _ao_scheme_bool_false) {
+		ao_scheme_stack->values = ao_scheme_v;
+		ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
+		ao_scheme_stack->state = eval_while;
+		if (!ao_scheme_stack_push())
+			return 0;
+		ao_scheme_stack->state = eval_begin;
+		ao_scheme_stack->sexprs = ao_scheme_v;
+	}
+	else
+	{
+		ao_scheme_stack->state = eval_val;
+		ao_scheme_v = ao_scheme_stack->values;
+	}
+	return 1;
+}
+
+/*
+ * Replace the original sexpr with the macro expansion, then
+ * execute that
+ */
+static int
+ao_scheme_eval_macro(void)
+{
+	DBGI("macro: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
+
+	if (ao_scheme_v == AO_SCHEME_NIL)
+		ao_scheme_abort();
+	if (ao_scheme_poly_type(ao_scheme_v) == AO_SCHEME_CONS) {
+		*ao_scheme_poly_cons(ao_scheme_stack->sexprs) = *ao_scheme_poly_cons(ao_scheme_v);
+		ao_scheme_v = ao_scheme_stack->sexprs;
+		DBGI("sexprs rewritten to: "); DBG_POLY(ao_scheme_v); DBG("\n");
+	}
+	ao_scheme_stack->sexprs = AO_SCHEME_NIL;
+	ao_scheme_stack->state = eval_sexpr;
+	return 1;
+}
+
+static int (*const evals[])(void) = {
+	[eval_sexpr] = ao_scheme_eval_sexpr,
+	[eval_val] = ao_scheme_eval_val,
+	[eval_formal] = ao_scheme_eval_formal,
+	[eval_exec] = ao_scheme_eval_exec,
+	[eval_apply] = ao_scheme_eval_apply,
+	[eval_cond] = ao_scheme_eval_cond,
+	[eval_cond_test] = ao_scheme_eval_cond_test,
+	[eval_begin] = ao_scheme_eval_begin,
+	[eval_while] = ao_scheme_eval_while,
+	[eval_while_test] = ao_scheme_eval_while_test,
+	[eval_macro] = ao_scheme_eval_macro,
+};
+
+const char * const ao_scheme_state_names[] = {
+	[eval_sexpr] = "sexpr",
+	[eval_val] = "val",
+	[eval_formal] = "formal",
+	[eval_exec] = "exec",
+	[eval_apply] = "apply",
+	[eval_cond] = "cond",
+	[eval_cond_test] = "cond_test",
+	[eval_begin] = "begin",
+	[eval_while] = "while",
+	[eval_while_test] = "while_test",
+	[eval_macro] = "macro",
+};
+
+/*
+ * Called at restore time to reset all execution state
+ */
+
+void
+ao_scheme_eval_clear_globals(void)
+{
+	ao_scheme_stack = NULL;
+	ao_scheme_frame_current = NULL;
+	ao_scheme_v = AO_SCHEME_NIL;
+}
+
+int
+ao_scheme_eval_restart(void)
+{
+	return ao_scheme_stack_push();
+}
+
+ao_poly
+ao_scheme_eval(ao_poly _v)
+{
+	ao_scheme_v = _v;
+
+	ao_scheme_frame_init();
+
+	if (!ao_scheme_stack_push())
+		return AO_SCHEME_NIL;
+
+	while (ao_scheme_stack) {
+		if (!(*evals[ao_scheme_stack->state])() || ao_scheme_exception) {
+			ao_scheme_stack_clear();
+			return AO_SCHEME_NIL;
+		}
+	}
+	DBG_DO(if (ao_scheme_frame_current) {DBGI("frame left as "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");});
+	ao_scheme_frame_current = NULL;
+	return ao_scheme_v;
+}
diff --git a/src/scheme/ao_scheme_float.c b/src/scheme/ao_scheme_float.c
new file mode 100644
index 00000000..541f0264
--- /dev/null
+++ b/src/scheme/ao_scheme_float.c
@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2017 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <math.h>
+
+static void float_mark(void *addr)
+{
+	(void) addr;
+}
+
+static int float_size(void *addr)
+{
+	if (!addr)
+		return 0;
+	return sizeof (struct ao_scheme_float);
+}
+
+static void float_move(void *addr)
+{
+	(void) addr;
+}
+
+const struct ao_scheme_type ao_scheme_float_type = {
+	.mark = float_mark,
+	.size = float_size,
+	.move = float_move,
+	.name = "float",
+};
+
+void
+ao_scheme_float_write(ao_poly p)
+{
+	struct ao_scheme_float *f = ao_scheme_poly_float(p);
+	float	v = f->value;
+
+	if (isnanf(v))
+		printf("+nan.0");
+	else if (isinff(v)) {
+		if (v < 0)
+			printf("-");
+		else
+			printf("+");
+		printf("inf.0");
+	} else
+		printf ("%g", f->value);
+}
+
+float
+ao_scheme_poly_number(ao_poly p)
+{
+	switch (ao_scheme_poly_base_type(p)) {
+	case AO_SCHEME_INT:
+		return ao_scheme_poly_int(p);
+	case AO_SCHEME_OTHER:
+		switch (ao_scheme_other_type(ao_scheme_poly_other(p))) {
+		case AO_SCHEME_BIGINT:
+			return ao_scheme_bigint_int(ao_scheme_poly_bigint(p)->value);
+		case AO_SCHEME_FLOAT:
+			return ao_scheme_poly_float(p)->value;
+		}
+	}
+	return NAN;
+}
+
+ao_poly
+ao_scheme_float_get(float value)
+{
+	struct ao_scheme_float	*f;
+
+	f = ao_scheme_alloc(sizeof (struct ao_scheme_float));
+	f->type = AO_SCHEME_FLOAT;
+	f->value = value;
+	return ao_scheme_float_poly(f);
+}
+
+ao_poly
+ao_scheme_do_inexactp(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (ao_scheme_poly_type(ao_scheme_arg(cons, 0)) == AO_SCHEME_FLOAT)
+		return _ao_scheme_bool_true;
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_finitep(struct ao_scheme_cons *cons)
+{
+	ao_poly	value;
+	float	f;
+
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	value = ao_scheme_arg(cons, 0);
+	switch (ao_scheme_poly_type(value)) {
+	case AO_SCHEME_INT:
+	case AO_SCHEME_BIGINT:
+		return _ao_scheme_bool_true;
+	case AO_SCHEME_FLOAT:
+		f = ao_scheme_poly_float(value)->value;
+		if (!isnan(f) && !isinf(f))
+			return _ao_scheme_bool_true;
+	}
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_infinitep(struct ao_scheme_cons *cons)
+{
+	ao_poly	value;
+	float	f;
+
+	if (!ao_scheme_check_argc(_ao_scheme_atom_led, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	value = ao_scheme_arg(cons, 0);
+	switch (ao_scheme_poly_type(value)) {
+	case AO_SCHEME_FLOAT:
+		f = ao_scheme_poly_float(value)->value;
+		if (isinf(f))
+			return _ao_scheme_bool_true;
+	}
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_sqrt(struct ao_scheme_cons *cons)
+{
+	ao_poly	value;
+
+	if (!ao_scheme_check_argc(_ao_scheme_atom_sqrt, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	value = ao_scheme_arg(cons, 0);
+	if (!ao_scheme_number_typep(ao_scheme_poly_type(value)))
+		return ao_scheme_error(AO_SCHEME_INVALID, "%s: non-numeric", ao_scheme_poly_atom(_ao_scheme_atom_sqrt)->name);
+	return ao_scheme_float_get(sqrtf(ao_scheme_poly_number(value)));
+}
diff --git a/src/scheme/ao_scheme_frame.c b/src/scheme/ao_scheme_frame.c
new file mode 100644
index 00000000..e5d481e7
--- /dev/null
+++ b/src/scheme/ao_scheme_frame.c
@@ -0,0 +1,330 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+static inline int
+frame_vals_num_size(int num)
+{
+	return sizeof (struct ao_scheme_frame_vals) + num * sizeof (struct ao_scheme_val);
+}
+
+static int
+frame_vals_size(void *addr)
+{
+	struct ao_scheme_frame_vals	*vals = addr;
+	return frame_vals_num_size(vals->size);
+}
+
+static void
+frame_vals_mark(void *addr)
+{
+	struct ao_scheme_frame_vals	*vals = addr;
+	int				f;
+
+	for (f = 0; f < vals->size; f++) {
+		struct ao_scheme_val	*v = &vals->vals[f];
+
+		ao_scheme_poly_mark(v->val, 0);
+		MDBG_MOVE("frame mark atom %s %d val %d at %d    ",
+			  ao_scheme_poly_atom(v->atom)->name,
+			  MDBG_OFFSET(ao_scheme_ref(v->atom)),
+			  MDBG_OFFSET(ao_scheme_ref(v->val)), f);
+		MDBG_DO(ao_scheme_poly_write(v->val));
+		MDBG_DO(printf("\n"));
+	}
+}
+
+static void
+frame_vals_move(void *addr)
+{
+	struct ao_scheme_frame_vals	*vals = addr;
+	int				f;
+
+	for (f = 0; f < vals->size; f++) {
+		struct ao_scheme_val	*v = &vals->vals[f];
+
+		ao_scheme_poly_move(&v->atom, 0);
+		ao_scheme_poly_move(&v->val, 0);
+		MDBG_MOVE("frame move atom %s %d val %d at %d\n",
+			  ao_scheme_poly_atom(v->atom)->name,
+			  MDBG_OFFSET(ao_scheme_ref(v->atom)),
+			  MDBG_OFFSET(ao_scheme_ref(v->val)), f);
+	}
+}
+
+const struct ao_scheme_type ao_scheme_frame_vals_type = {
+	.mark = frame_vals_mark,
+	.size = frame_vals_size,
+	.move = frame_vals_move,
+	.name = "frame_vals"
+};
+
+static int
+frame_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_frame);
+}
+
+static void
+frame_mark(void *addr)
+{
+	struct ao_scheme_frame	*frame = addr;
+
+	for (;;) {
+		MDBG_MOVE("frame mark %d\n", MDBG_OFFSET(frame));
+		if (!AO_SCHEME_IS_POOL(frame))
+			break;
+		ao_scheme_poly_mark(frame->vals, 0);
+		frame = ao_scheme_poly_frame(frame->prev);
+		MDBG_MOVE("frame next %d\n", MDBG_OFFSET(frame));
+		if (!frame)
+			break;
+		if (ao_scheme_mark_memory(&ao_scheme_frame_type, frame))
+			break;
+	}
+}
+
+static void
+frame_move(void *addr)
+{
+	struct ao_scheme_frame	*frame = addr;
+
+	for (;;) {
+		struct ao_scheme_frame	*prev;
+		int			ret;
+
+		MDBG_MOVE("frame move %d\n", MDBG_OFFSET(frame));
+		if (!AO_SCHEME_IS_POOL(frame))
+			break;
+		ao_scheme_poly_move(&frame->vals, 0);
+		prev = ao_scheme_poly_frame(frame->prev);
+		if (!prev)
+			break;
+		ret = ao_scheme_move_memory(&ao_scheme_frame_type, (void **) &prev);
+		if (prev != ao_scheme_poly_frame(frame->prev)) {
+			MDBG_MOVE("frame prev moved from %d to %d\n",
+				  MDBG_OFFSET(ao_scheme_poly_frame(frame->prev)),
+				  MDBG_OFFSET(prev));
+			frame->prev = ao_scheme_frame_poly(prev);
+		}
+		if (ret)
+			break;
+		frame = prev;
+	}
+}
+
+const struct ao_scheme_type ao_scheme_frame_type = {
+	.mark = frame_mark,
+	.size = frame_size,
+	.move = frame_move,
+	.name = "frame",
+};
+
+void
+ao_scheme_frame_write(ao_poly p)
+{
+	struct ao_scheme_frame		*frame = ao_scheme_poly_frame(p);
+	struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(frame->vals);
+	int				f;
+
+	printf ("{");
+	if (frame) {
+		if (frame->type & AO_SCHEME_FRAME_PRINT)
+			printf("recurse...");
+		else {
+			frame->type |= AO_SCHEME_FRAME_PRINT;
+			for (f = 0; f < frame->num; f++) {
+				if (f != 0)
+					printf(", ");
+				ao_scheme_poly_write(vals->vals[f].atom);
+				printf(" = ");
+				ao_scheme_poly_write(vals->vals[f].val);
+			}
+			if (frame->prev)
+				ao_scheme_poly_write(frame->prev);
+			frame->type &= ~AO_SCHEME_FRAME_PRINT;
+		}
+	}
+	printf("}");
+}
+
+static int
+ao_scheme_frame_find(struct ao_scheme_frame *frame, int top, ao_poly atom)
+{
+	struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(frame->vals);
+	int 				l = 0;
+	int 				r = top - 1;
+
+	while (l <= r) {
+		int m = (l + r) >> 1;
+		if (vals->vals[m].atom < atom)
+			l = m + 1;
+		else
+			r = m - 1;
+	}
+	return l;
+}
+
+ao_poly *
+ao_scheme_frame_ref(struct ao_scheme_frame *frame, ao_poly atom)
+{
+	struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(frame->vals);
+	int				l = ao_scheme_frame_find(frame, frame->num, atom);
+
+	if (l >= frame->num)
+		return NULL;
+
+	if (vals->vals[l].atom != atom)
+		return NULL;
+	return &vals->vals[l].val;
+}
+
+struct ao_scheme_frame	*ao_scheme_frame_free_list[AO_SCHEME_FRAME_FREE];
+
+static struct ao_scheme_frame_vals *
+ao_scheme_frame_vals_new(int num)
+{
+	struct ao_scheme_frame_vals	*vals;
+
+	vals = ao_scheme_alloc(frame_vals_num_size(num));
+	if (!vals)
+		return NULL;
+	vals->type = AO_SCHEME_FRAME_VALS;
+	vals->size = num;
+	memset(vals->vals, '\0', num * sizeof (struct ao_scheme_val));
+	return vals;
+}
+
+struct ao_scheme_frame *
+ao_scheme_frame_new(int num)
+{
+	struct ao_scheme_frame		*frame;
+	struct ao_scheme_frame_vals	*vals;
+
+	if (num < AO_SCHEME_FRAME_FREE && (frame = ao_scheme_frame_free_list[num])) {
+		ao_scheme_frame_free_list[num] = ao_scheme_poly_frame(frame->prev);
+		vals = ao_scheme_poly_frame_vals(frame->vals);
+	} else {
+		frame = ao_scheme_alloc(sizeof (struct ao_scheme_frame));
+		if (!frame)
+			return NULL;
+		frame->type = AO_SCHEME_FRAME;
+		frame->num = 0;
+		frame->prev = AO_SCHEME_NIL;
+		frame->vals = AO_SCHEME_NIL;
+		ao_scheme_frame_stash(0, frame);
+		vals = ao_scheme_frame_vals_new(num);
+		frame = ao_scheme_frame_fetch(0);
+		if (!vals)
+			return NULL;
+		frame->vals = ao_scheme_frame_vals_poly(vals);
+		frame->num = num;
+	}
+	frame->prev = AO_SCHEME_NIL;
+	return frame;
+}
+
+ao_poly
+ao_scheme_frame_mark(struct ao_scheme_frame *frame)
+{
+	if (!frame)
+		return AO_SCHEME_NIL;
+	frame->type |= AO_SCHEME_FRAME_MARK;
+	return ao_scheme_frame_poly(frame);
+}
+
+void
+ao_scheme_frame_free(struct ao_scheme_frame *frame)
+{
+	if (frame && !ao_scheme_frame_marked(frame)) {
+		int	num = frame->num;
+		if (num < AO_SCHEME_FRAME_FREE) {
+			struct ao_scheme_frame_vals	*vals;
+
+			vals = ao_scheme_poly_frame_vals(frame->vals);
+			memset(vals->vals, '\0', vals->size * sizeof (struct ao_scheme_val));
+			frame->prev = ao_scheme_frame_poly(ao_scheme_frame_free_list[num]);
+			ao_scheme_frame_free_list[num] = frame;
+		}
+	}
+}
+
+static struct ao_scheme_frame *
+ao_scheme_frame_realloc(struct ao_scheme_frame *frame, int new_num)
+{
+	struct ao_scheme_frame_vals	*vals;
+	struct ao_scheme_frame_vals	*new_vals;
+	int				copy;
+
+	if (new_num == frame->num)
+		return frame;
+	ao_scheme_frame_stash(0, frame);
+	new_vals = ao_scheme_frame_vals_new(new_num);
+	frame = ao_scheme_frame_fetch(0);
+	if (!new_vals)
+		return NULL;
+	vals = ao_scheme_poly_frame_vals(frame->vals);
+	copy = new_num;
+	if (copy > frame->num)
+		copy = frame->num;
+	memcpy(new_vals->vals, vals->vals, copy * sizeof (struct ao_scheme_val));
+	frame->vals = ao_scheme_frame_vals_poly(new_vals);
+	frame->num = new_num;
+	return frame;
+}
+
+void
+ao_scheme_frame_bind(struct ao_scheme_frame *frame, int num, ao_poly atom, ao_poly val)
+{
+	struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(frame->vals);
+	int 				l = ao_scheme_frame_find(frame, num, atom);
+
+	memmove(&vals->vals[l+1],
+		&vals->vals[l],
+		(num - l) * sizeof (struct ao_scheme_val));
+	vals->vals[l].atom = atom;
+	vals->vals[l].val = val;
+}
+
+ao_poly
+ao_scheme_frame_add(struct ao_scheme_frame *frame, ao_poly atom, ao_poly val)
+{
+	ao_poly *ref = frame ? ao_scheme_frame_ref(frame, atom) : NULL;
+
+	if (!ref) {
+		int f = frame->num;
+		ao_scheme_poly_stash(0, atom);
+		ao_scheme_poly_stash(1, val);
+		frame = ao_scheme_frame_realloc(frame, f + 1);
+		val = ao_scheme_poly_fetch(1);
+		atom = ao_scheme_poly_fetch(0);
+		if (!frame)
+			return AO_SCHEME_NIL;
+		ao_scheme_frame_bind(frame, frame->num - 1, atom, val);
+	} else
+		*ref = val;
+	return val;
+}
+
+struct ao_scheme_frame	*ao_scheme_frame_global;
+struct ao_scheme_frame	*ao_scheme_frame_current;
+
+void
+ao_scheme_frame_init(void)
+{
+	if (!ao_scheme_frame_global)
+		ao_scheme_frame_global = ao_scheme_frame_new(0);
+}
diff --git a/src/scheme/ao_scheme_int.c b/src/scheme/ao_scheme_int.c
new file mode 100644
index 00000000..350a5d35
--- /dev/null
+++ b/src/scheme/ao_scheme_int.c
@@ -0,0 +1,79 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+void
+ao_scheme_int_write(ao_poly p)
+{
+	int i = ao_scheme_poly_int(p);
+	printf("%d", i);
+}
+
+int32_t
+ao_scheme_poly_integer(ao_poly p)
+{
+	switch (ao_scheme_poly_base_type(p)) {
+	case AO_SCHEME_INT:
+		return ao_scheme_poly_int(p);
+	case AO_SCHEME_OTHER:
+		if (ao_scheme_other_type(ao_scheme_poly_other(p)) == AO_SCHEME_BIGINT)
+			return ao_scheme_bigint_int(ao_scheme_poly_bigint(p)->value);
+	}
+	return AO_SCHEME_NOT_INTEGER;
+}
+
+ao_poly
+ao_scheme_integer_poly(int32_t p)
+{
+	struct ao_scheme_bigint	*bi;
+
+	if (AO_SCHEME_MIN_INT <= p && p <= AO_SCHEME_MAX_INT)
+		return ao_scheme_int_poly(p);
+	bi = ao_scheme_alloc(sizeof (struct ao_scheme_bigint));
+	bi->value = ao_scheme_int_bigint(p);
+	return ao_scheme_bigint_poly(bi);
+}
+
+static void bigint_mark(void *addr)
+{
+	(void) addr;
+}
+
+static int bigint_size(void *addr)
+{
+	if (!addr)
+		return 0;
+	return sizeof (struct ao_scheme_bigint);
+}
+
+static void bigint_move(void *addr)
+{
+	(void) addr;
+}
+
+const struct ao_scheme_type ao_scheme_bigint_type = {
+	.mark = bigint_mark,
+	.size = bigint_size,
+	.move = bigint_move,
+	.name = "bigint",
+};
+
+void
+ao_scheme_bigint_write(ao_poly p)
+{
+	struct ao_scheme_bigint	*bi = ao_scheme_poly_bigint(p);
+
+	printf("%d", ao_scheme_bigint_int(bi->value));
+}
diff --git a/src/scheme/ao_scheme_lambda.c b/src/scheme/ao_scheme_lambda.c
new file mode 100644
index 00000000..ec6f858c
--- /dev/null
+++ b/src/scheme/ao_scheme_lambda.c
@@ -0,0 +1,208 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao_scheme.h"
+
+int
+lambda_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_lambda);
+}
+
+void
+lambda_mark(void *addr)
+{
+	struct ao_scheme_lambda	*lambda = addr;
+
+	ao_scheme_poly_mark(lambda->code, 0);
+	ao_scheme_poly_mark(lambda->frame, 0);
+}
+
+void
+lambda_move(void *addr)
+{
+	struct ao_scheme_lambda	*lambda = addr;
+
+	ao_scheme_poly_move(&lambda->code, 0);
+	ao_scheme_poly_move(&lambda->frame, 0);
+}
+
+const struct ao_scheme_type ao_scheme_lambda_type = {
+	.size = lambda_size,
+	.mark = lambda_mark,
+	.move = lambda_move,
+	.name = "lambda",
+};
+
+void
+ao_scheme_lambda_write(ao_poly poly)
+{
+	struct ao_scheme_lambda	*lambda = ao_scheme_poly_lambda(poly);
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(lambda->code);
+
+	printf("(");
+	printf("%s", ao_scheme_args_name(lambda->args));
+	while (cons) {
+		printf(" ");
+		ao_scheme_poly_write(cons->car);
+		cons = ao_scheme_poly_cons(cons->cdr);
+	}
+	printf(")");
+}
+
+ao_poly
+ao_scheme_lambda_alloc(struct ao_scheme_cons *code, int args)
+{
+	struct ao_scheme_lambda	*lambda;
+	ao_poly			formal;
+	struct ao_scheme_cons	*cons;
+
+	formal = ao_scheme_arg(code, 0);
+	while (formal != AO_SCHEME_NIL) {
+		switch (ao_scheme_poly_type(formal)) {
+		case AO_SCHEME_CONS:
+			cons = ao_scheme_poly_cons(formal);
+			if (ao_scheme_poly_type(cons->car) != AO_SCHEME_ATOM)
+				return ao_scheme_error(AO_SCHEME_INVALID, "formal %p is not atom", cons->car);
+			formal = cons->cdr;
+			break;
+		case AO_SCHEME_ATOM:
+			formal = AO_SCHEME_NIL;
+			break;
+		default:
+			return ao_scheme_error(AO_SCHEME_INVALID, "formal %p is not atom", formal);
+		}
+	}
+
+	ao_scheme_cons_stash(0, code);
+	lambda = ao_scheme_alloc(sizeof (struct ao_scheme_lambda));
+	code = ao_scheme_cons_fetch(0);
+	if (!lambda)
+		return AO_SCHEME_NIL;
+
+	lambda->type = AO_SCHEME_LAMBDA;
+	lambda->args = args;
+	lambda->code = ao_scheme_cons_poly(code);
+	lambda->frame = ao_scheme_frame_mark(ao_scheme_frame_current);
+	DBGI("build frame: "); DBG_POLY(lambda->frame); DBG("\n");
+	DBG_STACK();
+	return ao_scheme_lambda_poly(lambda);
+}
+
+ao_poly
+ao_scheme_do_lambda(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_lambda_alloc(cons, AO_SCHEME_FUNC_LAMBDA);
+}
+
+ao_poly
+ao_scheme_do_nlambda(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_lambda_alloc(cons, AO_SCHEME_FUNC_NLAMBDA);
+}
+
+ao_poly
+ao_scheme_do_macro(struct ao_scheme_cons *cons)
+{
+	return ao_scheme_lambda_alloc(cons, AO_SCHEME_FUNC_MACRO);
+}
+
+ao_poly
+ao_scheme_lambda_eval(void)
+{
+	struct ao_scheme_lambda	*lambda = ao_scheme_poly_lambda(ao_scheme_v);
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(ao_scheme_stack->values);
+	struct ao_scheme_cons	*code = ao_scheme_poly_cons(lambda->code);
+	ao_poly			formals;
+	struct ao_scheme_frame	*next_frame;
+	int			args_wanted;
+	ao_poly			varargs = AO_SCHEME_NIL;
+	int			args_provided;
+	int			f;
+	struct ao_scheme_cons	*vals;
+
+	DBGI("lambda "); DBG_POLY(ao_scheme_lambda_poly(lambda)); DBG("\n");
+
+	args_wanted = 0;
+	for (formals = ao_scheme_arg(code, 0);
+	     ao_scheme_is_pair(formals);
+	     formals = ao_scheme_poly_cons(formals)->cdr)
+		++args_wanted;
+	if (formals != AO_SCHEME_NIL) {
+		if (ao_scheme_poly_type(formals) != AO_SCHEME_ATOM)
+			return ao_scheme_error(AO_SCHEME_INVALID, "bad lambda form");
+		varargs = formals;
+	}
+
+	/* Create a frame to hold the variables
+	 */
+	args_provided = ao_scheme_cons_length(cons) - 1;
+	if (varargs == AO_SCHEME_NIL) {
+		if (args_wanted != args_provided)
+			return ao_scheme_error(AO_SCHEME_INVALID, "need %d args, got %d", args_wanted, args_provided);
+	} else {
+		if (args_provided < args_wanted)
+			return ao_scheme_error(AO_SCHEME_INVALID, "need at least %d args, got %d", args_wanted, args_provided);
+	}
+
+	ao_scheme_poly_stash(1, varargs);
+	next_frame = ao_scheme_frame_new(args_wanted + (varargs != AO_SCHEME_NIL));
+	varargs = ao_scheme_poly_fetch(1);
+	if (!next_frame)
+		return AO_SCHEME_NIL;
+
+	/* Re-fetch all of the values in case something moved */
+	lambda = ao_scheme_poly_lambda(ao_scheme_v);
+	cons = ao_scheme_poly_cons(ao_scheme_stack->values);
+	code = ao_scheme_poly_cons(lambda->code);
+	formals = ao_scheme_arg(code, 0);
+	vals = ao_scheme_poly_cons(cons->cdr);
+
+	next_frame->prev = lambda->frame;
+	ao_scheme_frame_current = next_frame;
+	ao_scheme_stack->frame = ao_scheme_frame_poly(ao_scheme_frame_current);
+
+	for (f = 0; f < args_wanted; f++) {
+		struct ao_scheme_cons *arg = ao_scheme_poly_cons(formals);
+		DBGI("bind "); DBG_POLY(arg->car); DBG(" = "); DBG_POLY(vals->car); DBG("\n");
+		ao_scheme_frame_bind(next_frame, f, arg->car, vals->car);
+		formals = arg->cdr;
+		vals = ao_scheme_poly_cons(vals->cdr);
+	}
+	if (varargs) {
+		DBGI("bind "); DBG_POLY(varargs); DBG(" = "); DBG_POLY(ao_scheme_cons_poly(vals)); DBG("\n");
+		/*
+		 * Bind the rest of the arguments to the final parameter
+		 */
+		ao_scheme_frame_bind(next_frame, f, varargs, ao_scheme_cons_poly(vals));
+	} else {
+		/*
+		 * Mark the cons cells from the actuals as freed for immediate re-use, unless
+		 * the actuals point into the source function (nlambdas and macros), or if the
+		 * stack containing them was copied as a part of a continuation
+		 */
+		if (lambda->args == AO_SCHEME_FUNC_LAMBDA && !ao_scheme_stack_marked(ao_scheme_stack)) {
+			ao_scheme_stack->values = AO_SCHEME_NIL;
+			ao_scheme_cons_free(cons);
+		}
+	}
+	DBGI("eval frame: "); DBG_POLY(ao_scheme_frame_poly(next_frame)); DBG("\n");
+	DBG_STACK();
+	DBGI("eval code: "); DBG_POLY(code->cdr); DBG("\n");
+	return code->cdr;
+}
diff --git a/src/scheme/ao_scheme_lex.c b/src/scheme/ao_scheme_lex.c
new file mode 100644
index 00000000..266b1fc0
--- /dev/null
+++ b/src/scheme/ao_scheme_lex.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
diff --git a/src/scheme/ao_scheme_make_builtin b/src/scheme/ao_scheme_make_builtin
new file mode 100644
index 00000000..8e9c2c0b
--- /dev/null
+++ b/src/scheme/ao_scheme_make_builtin
@@ -0,0 +1,190 @@
+#!/usr/bin/nickle
+
+typedef struct {
+	string	type;
+	string	c_name;
+	string[*]	lisp_names;
+} builtin_t;
+
+string[string] type_map = {
+	"lambda" => "LAMBDA",
+	"nlambda" => "NLAMBDA",
+	"macro" => "MACRO",
+	"f_lambda" => "F_LAMBDA",
+	"atom" => "atom",
+};
+
+string[*]
+make_lisp(string[*] tokens)
+{
+	string[...] lisp = {};
+
+	if (dim(tokens) < 3)
+		return (string[1]) { tokens[dim(tokens) - 1] };
+	return (string[dim(tokens)-2]) { [i] = tokens[i+2] };
+}
+
+builtin_t
+read_builtin(file f) {
+	string	line = File::fgets(f);
+	string[*]	tokens = String::wordsplit(line, " \t");
+
+	return (builtin_t) {
+		.type = dim(tokens) > 0 ? type_map[tokens[0]] : "#",
+		.c_name = dim(tokens) > 1 ? tokens[1] : "#",
+		.lisp_names = make_lisp(tokens),
+	};
+}
+
+builtin_t[*]
+read_builtins(file f) {
+	builtin_t[...] builtins = {};
+
+	while (!File::end(f)) {
+		builtin_t	b = read_builtin(f);
+
+		if (b.type[0] != '#')
+			builtins[dim(builtins)] = b;
+	}
+	return builtins;
+}
+
+bool is_atom(builtin_t b) = b.type == "atom";
+
+void
+dump_ids(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_ID\n");
+	printf("#undef AO_SCHEME_BUILTIN_ID\n");
+	printf("enum ao_scheme_builtin_id {\n");
+	for (int i = 0; i < dim(builtins); i++)
+		if (!is_atom(builtins[i]))
+			printf("\tbuiltin_%s,\n", builtins[i].c_name);
+	printf("\t_builtin_last\n");
+	printf("};\n");
+	printf("#endif /* AO_SCHEME_BUILTIN_ID */\n");
+}
+
+void
+dump_casename(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_CASENAME\n");
+	printf("#undef AO_SCHEME_BUILTIN_CASENAME\n");
+	printf("static char *ao_scheme_builtin_name(enum ao_scheme_builtin_id b) {\n");
+	printf("\tswitch(b) {\n");
+	for (int i = 0; i < dim(builtins); i++)
+		if (!is_atom(builtins[i]))
+			printf("\tcase builtin_%s: return ao_scheme_poly_atom(_atom(\"%s\"))->name;\n",
+			       builtins[i].c_name, builtins[i].lisp_names[0]);
+	printf("\tdefault: return \"???\";\n");
+	printf("\t}\n");
+	printf("}\n");
+	printf("#endif /* AO_SCHEME_BUILTIN_CASENAME */\n");
+}
+
+void
+cify_lisp(string l) {
+	for (int j = 0; j < String::length(l); j++) {
+		int c= l[j];
+		if (Ctype::isalnum(c) || c == '_')
+			printf("%c", c);
+		else
+			printf("%02x", c);
+	}
+}
+
+void
+dump_arrayname(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_ARRAYNAME\n");
+	printf("#undef AO_SCHEME_BUILTIN_ARRAYNAME\n");
+	printf("static const ao_poly builtin_names[] = {\n");
+	for (int i = 0; i < dim(builtins); i++) {
+		if (!is_atom(builtins[i])) {
+			printf("\t[builtin_%s] = _ao_scheme_atom_",
+			       builtins[i].c_name);
+			cify_lisp(builtins[i].lisp_names[0]);
+			printf(",\n");
+		}
+	}
+	printf("};\n");
+	printf("#endif /* AO_SCHEME_BUILTIN_ARRAYNAME */\n");
+}
+
+void
+dump_funcs(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_FUNCS\n");
+	printf("#undef AO_SCHEME_BUILTIN_FUNCS\n");
+	printf("const ao_scheme_func_t ao_scheme_builtins[] = {\n");
+	for (int i = 0; i < dim(builtins); i++) {
+		if (!is_atom(builtins[i]))
+			printf("\t[builtin_%s] = ao_scheme_do_%s,\n",
+			       builtins[i].c_name,
+			       builtins[i].c_name);
+	}
+	printf("};\n");
+	printf("#endif /* AO_SCHEME_BUILTIN_FUNCS */\n");
+}
+
+void
+dump_decls(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_DECLS\n");
+	printf("#undef AO_SCHEME_BUILTIN_DECLS\n");
+	for (int i = 0; i < dim(builtins); i++) {
+		if (!is_atom(builtins[i])) {
+			printf("ao_poly\n");
+			printf("ao_scheme_do_%s(struct ao_scheme_cons *cons);\n",
+			       builtins[i].c_name);
+		}
+	}
+	printf("#endif /* AO_SCHEME_BUILTIN_DECLS */\n");
+}
+
+void
+dump_consts(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_CONSTS\n");
+	printf("#undef AO_SCHEME_BUILTIN_CONSTS\n");
+	printf("struct builtin_func funcs[] = {\n");
+	for (int i = 0; i < dim(builtins); i++) {
+		if (!is_atom(builtins[i])) {
+			for (int j = 0; j < dim(builtins[i].lisp_names); j++) {
+				printf ("\t{ .name = \"%s\", .args = AO_SCHEME_FUNC_%s, .func = builtin_%s },\n",
+					builtins[i].lisp_names[j],
+					builtins[i].type,
+					builtins[i].c_name);
+			}
+		}
+	}
+	printf("};\n");
+	printf("#endif /* AO_SCHEME_BUILTIN_CONSTS */\n");
+}
+
+void
+dump_atoms(builtin_t[*] builtins) {
+	printf("#ifdef AO_SCHEME_BUILTIN_ATOMS\n");
+	printf("#undef AO_SCHEME_BUILTIN_ATOMS\n");
+	for (int i = 0; i < dim(builtins); i++) {
+		for (int j = 0; j < dim(builtins[i].lisp_names); j++) {
+			printf("#define _ao_scheme_atom_");
+			cify_lisp(builtins[i].lisp_names[j]);
+			printf(" _atom(\"%s\")\n", builtins[i].lisp_names[j]);
+		}
+	}
+	printf("#endif /* AO_SCHEME_BUILTIN_ATOMS */\n");
+}
+
+void main() {
+	if (dim(argv) < 2) {
+		File::fprintf(stderr, "usage: %s <file>\n", argv[0]);
+		exit(1);
+	}
+	twixt(file f = File::open(argv[1], "r"); File::close(f)) {
+		builtin_t[*]	builtins = read_builtins(f);
+		dump_ids(builtins);
+		dump_casename(builtins);
+		dump_arrayname(builtins);
+		dump_funcs(builtins);
+		dump_decls(builtins);
+		dump_consts(builtins);
+		dump_atoms(builtins);
+	}
+}
+
+main();
diff --git a/src/scheme/ao_scheme_make_const.c b/src/scheme/ao_scheme_make_const.c
new file mode 100644
index 00000000..cf42ec52
--- /dev/null
+++ b/src/scheme/ao_scheme_make_const.c
@@ -0,0 +1,395 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <stdlib.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <getopt.h>
+
+static struct ao_scheme_builtin *
+ao_scheme_make_builtin(enum ao_scheme_builtin_id func, int args) {
+	struct ao_scheme_builtin *b = ao_scheme_alloc(sizeof (struct ao_scheme_builtin));
+
+	b->type = AO_SCHEME_BUILTIN;
+	b->func = func;
+	b->args = args;
+	return b;
+}
+
+struct builtin_func {
+	char	*name;
+	int	args;
+	enum ao_scheme_builtin_id	func;
+};
+
+#define AO_SCHEME_BUILTIN_CONSTS
+#include "ao_scheme_builtin.h"
+
+#define N_FUNC (sizeof funcs / sizeof funcs[0])
+
+struct ao_scheme_frame	*globals;
+
+static int
+is_atom(int offset)
+{
+	struct ao_scheme_atom *a;
+
+	for (a = ao_scheme_atoms; a; a = ao_scheme_poly_atom(a->next))
+		if (((uint8_t *) a->name - ao_scheme_const) == offset)
+			return strlen(a->name);
+	return 0;
+}
+
+#define AO_FEC_CRC_INIT	0xffff
+
+static inline uint16_t
+ao_fec_crc_byte(uint8_t byte, uint16_t crc)
+{
+	uint8_t	bit;
+
+	for (bit = 0; bit < 8; bit++) {
+		if (((crc & 0x8000) >> 8) ^ (byte & 0x80))
+			crc = (crc << 1) ^ 0x8005;
+		else
+			crc = (crc << 1);
+		byte <<= 1;
+	}
+	return crc;
+}
+
+uint16_t
+ao_fec_crc(const uint8_t *bytes, uint8_t len)
+{
+	uint16_t	crc = AO_FEC_CRC_INIT;
+
+	while (len--)
+		crc = ao_fec_crc_byte(*bytes++, crc);
+	return crc;
+}
+
+struct ao_scheme_macro_stack {
+	struct ao_scheme_macro_stack *next;
+	ao_poly	p;
+};
+
+struct ao_scheme_macro_stack *macro_stack;
+
+int
+ao_scheme_macro_push(ao_poly p)
+{
+	struct ao_scheme_macro_stack *m = macro_stack;
+
+	while (m) {
+		if (m->p == p)
+			return 1;
+		m = m->next;
+	}
+	m = malloc (sizeof (struct ao_scheme_macro_stack));
+	m->p = p;
+	m->next = macro_stack;
+	macro_stack = m;
+	return 0;
+}
+
+void
+ao_scheme_macro_pop(void)
+{
+	struct ao_scheme_macro_stack *m = macro_stack;
+
+	macro_stack = m->next;
+	free(m);
+}
+
+#define DBG_MACRO 0
+#if DBG_MACRO
+int macro_scan_depth;
+
+void indent(void)
+{
+	int i;
+	for (i = 0; i < macro_scan_depth; i++)
+		printf("  ");
+}
+#define MACRO_DEBUG(a)	a
+#else
+#define MACRO_DEBUG(a)
+#endif
+
+ao_poly
+ao_has_macro(ao_poly p);
+
+ao_poly
+ao_macro_test_get(ao_poly atom)
+{
+	ao_poly	*ref = ao_scheme_atom_ref(atom, NULL);
+	if (ref)
+		return *ref;
+	return AO_SCHEME_NIL;
+}
+
+ao_poly
+ao_is_macro(ao_poly p)
+{
+	struct ao_scheme_builtin	*builtin;
+	struct ao_scheme_lambda	*lambda;
+	ao_poly ret;
+
+	MACRO_DEBUG(indent(); printf ("is macro "); ao_scheme_poly_write(p); printf("\n"); ++macro_scan_depth);
+	switch (ao_scheme_poly_type(p)) {
+	case AO_SCHEME_ATOM:
+		if (ao_scheme_macro_push(p))
+			ret = AO_SCHEME_NIL;
+		else {
+			if (ao_is_macro(ao_macro_test_get(p)))
+				ret = p;
+			else
+				ret = AO_SCHEME_NIL;
+			ao_scheme_macro_pop();
+		}
+		break;
+	case AO_SCHEME_CONS:
+		ret = ao_has_macro(p);
+		break;
+	case AO_SCHEME_BUILTIN:
+		builtin = ao_scheme_poly_builtin(p);
+		if ((builtin->args & AO_SCHEME_FUNC_MASK) == AO_SCHEME_FUNC_MACRO)
+			ret = p;
+		else
+			ret = 0;
+		break;
+
+	case AO_SCHEME_LAMBDA:
+		lambda = ao_scheme_poly_lambda(p);
+		if (lambda->args == AO_SCHEME_FUNC_MACRO)
+			ret = p;
+		else
+			ret = ao_has_macro(lambda->code);
+		break;
+	default:
+		ret = AO_SCHEME_NIL;
+		break;
+	}
+	MACRO_DEBUG(--macro_scan_depth;	indent(); printf ("... "); ao_scheme_poly_write(ret); printf("\n"));
+	return ret;
+}
+
+ao_poly
+ao_has_macro(ao_poly p)
+{
+	struct ao_scheme_cons	*cons;
+	struct ao_scheme_lambda	*lambda;
+	ao_poly			m;
+	ao_poly			list;
+
+	if (p == AO_SCHEME_NIL)
+		return AO_SCHEME_NIL;
+
+	MACRO_DEBUG(indent(); printf("has macro "); ao_scheme_poly_write(p); printf("\n"); ++macro_scan_depth);
+	switch (ao_scheme_poly_type(p)) {
+	case AO_SCHEME_LAMBDA:
+		lambda = ao_scheme_poly_lambda(p);
+		p = ao_has_macro(lambda->code);
+		break;
+	case AO_SCHEME_CONS:
+		cons = ao_scheme_poly_cons(p);
+		if ((p = ao_is_macro(cons->car)))
+			break;
+
+		list = cons->cdr;
+		p = AO_SCHEME_NIL;
+		while (list != AO_SCHEME_NIL && ao_scheme_poly_type(list) == AO_SCHEME_CONS) {
+			cons = ao_scheme_poly_cons(list);
+			m = ao_has_macro(cons->car);
+			if (m) {
+				p = m;
+				break;
+			}
+			list = cons->cdr;
+		}
+		break;
+
+	default:
+		p = AO_SCHEME_NIL;
+		break;
+	}
+	MACRO_DEBUG(--macro_scan_depth;	indent(); printf("... "); ao_scheme_poly_write(p); printf("\n"));
+	return p;
+}
+
+int
+ao_scheme_read_eval_abort(void)
+{
+	ao_poly	in, out = AO_SCHEME_NIL;
+	for(;;) {
+		in = ao_scheme_read();
+		if (in == _ao_scheme_atom_eof)
+			break;
+		out = ao_scheme_eval(in);
+		if (ao_scheme_exception)
+			return 0;
+		ao_scheme_poly_write(out);
+		putchar ('\n');
+	}
+	return 1;
+}
+
+static FILE	*in;
+static FILE	*out;
+
+int
+ao_scheme_getc(void)
+{
+	return getc(in);
+}
+
+static const struct option options[] = {
+	{ .name = "out", .has_arg = 1, .val = 'o' },
+	{ 0, 0, 0, 0 }
+};
+
+static void usage(char *program)
+{
+	fprintf(stderr, "usage: %s [--out=<output>] [input]\n", program);
+	exit(1);
+}
+
+int
+main(int argc, char **argv)
+{
+	int	f, o;
+	ao_poly	val;
+	struct ao_scheme_atom	*a;
+	struct ao_scheme_builtin	*b;
+	int	in_atom = 0;
+	char	*out_name = NULL;
+	int	c;
+	enum ao_scheme_builtin_id	prev_func;
+
+	in = stdin;
+	out = stdout;
+
+	while ((c = getopt_long(argc, argv, "o:", options, NULL)) != -1) {
+		switch (c) {
+		case 'o':
+			out_name = optarg;
+			break;
+		default:
+			usage(argv[0]);
+			break;
+		}
+	}
+
+	ao_scheme_frame_init();
+
+	/* Boolean values #f and #t */
+	ao_scheme_bool_get(0);
+	ao_scheme_bool_get(1);
+
+	prev_func = _builtin_last;
+	for (f = 0; f < (int) N_FUNC; f++) {
+		if (funcs[f].func != prev_func)
+			b = ao_scheme_make_builtin(funcs[f].func, funcs[f].args);
+		a = ao_scheme_atom_intern(funcs[f].name);
+		ao_scheme_atom_def(ao_scheme_atom_poly(a),
+				 ao_scheme_builtin_poly(b));
+	}
+
+	/* end of file value */
+	a = ao_scheme_atom_intern("eof");
+	ao_scheme_atom_def(ao_scheme_atom_poly(a),
+			 ao_scheme_atom_poly(a));
+
+	/* 'else' */
+	a = ao_scheme_atom_intern("else");
+
+	if (argv[optind]){
+		in = fopen(argv[optind], "r");
+		if (!in) {
+			perror(argv[optind]);
+			exit(1);
+		}
+	}
+	if (!ao_scheme_read_eval_abort()) {
+		fprintf(stderr, "eval failed\n");
+		exit(1);
+	}
+
+	/* Reduce to referenced values */
+	ao_scheme_collect(AO_SCHEME_COLLECT_FULL);
+
+	for (f = 0; f < ao_scheme_frame_global->num; f++) {
+		struct ao_scheme_frame_vals	*vals = ao_scheme_poly_frame_vals(ao_scheme_frame_global->vals);
+		val = ao_has_macro(vals->vals[f].val);
+		if (val != AO_SCHEME_NIL) {
+			printf("error: function %s contains unresolved macro: ",
+			       ao_scheme_poly_atom(vals->vals[f].atom)->name);
+			ao_scheme_poly_write(val);
+			printf("\n");
+			exit(1);
+		}
+	}
+
+	if (out_name) {
+		out = fopen(out_name, "w");
+		if (!out) {
+			perror(out_name);
+			exit(1);
+		}
+	}
+
+	fprintf(out, "/* Generated file, do not edit */\n\n");
+
+	fprintf(out, "#define AO_SCHEME_POOL_CONST %d\n", ao_scheme_top);
+	fprintf(out, "extern const uint8_t ao_scheme_const[AO_SCHEME_POOL_CONST] __attribute__((aligned(4)));\n");
+	fprintf(out, "#define ao_builtin_atoms 0x%04x\n", ao_scheme_atom_poly(ao_scheme_atoms));
+	fprintf(out, "#define ao_builtin_frame 0x%04x\n", ao_scheme_frame_poly(ao_scheme_frame_global));
+	fprintf(out, "#define ao_scheme_const_checksum ((uint16_t) 0x%04x)\n", ao_fec_crc(ao_scheme_const, ao_scheme_top));
+
+	fprintf(out, "#define _ao_scheme_bool_false 0x%04x\n", ao_scheme_bool_poly(ao_scheme_false));
+	fprintf(out, "#define _ao_scheme_bool_true 0x%04x\n", ao_scheme_bool_poly(ao_scheme_true));
+
+	for (a = ao_scheme_atoms; a; a = ao_scheme_poly_atom(a->next)) {
+		char	*n = a->name, c;
+		fprintf(out, "#define _ao_scheme_atom_");
+		while ((c = *n++)) {
+			if (isalnum(c))
+				fprintf(out, "%c", c);
+			else
+				fprintf(out, "%02x", c);
+		}
+		fprintf(out, "  0x%04x\n", ao_scheme_atom_poly(a));
+	}
+	fprintf(out, "#ifdef AO_SCHEME_CONST_BITS\n");
+	fprintf(out, "const uint8_t ao_scheme_const[AO_SCHEME_POOL_CONST] __attribute((aligned(4))) = {");
+	for (o = 0; o < ao_scheme_top; o++) {
+		uint8_t	c;
+		if ((o & 0xf) == 0)
+			fprintf(out, "\n\t");
+		else
+			fprintf(out, " ");
+		c = ao_scheme_const[o];
+		if (!in_atom)
+			in_atom = is_atom(o);
+		if (in_atom) {
+			fprintf(out, " '%c',", c);
+			in_atom--;
+		} else {
+			fprintf(out, "0x%02x,", c);
+		}
+	}
+	fprintf(out, "\n};\n");
+	fprintf(out, "#endif /* AO_SCHEME_CONST_BITS */\n");
+	exit(0);
+}
diff --git a/src/scheme/ao_scheme_mem.c b/src/scheme/ao_scheme_mem.c
new file mode 100644
index 00000000..acc726c8
--- /dev/null
+++ b/src/scheme/ao_scheme_mem.c
@@ -0,0 +1,968 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#define AO_SCHEME_CONST_BITS
+
+#include "ao_scheme.h"
+#include <stdio.h>
+#include <assert.h>
+
+#ifdef AO_SCHEME_MAKE_CONST
+
+/*
+ * When building the constant table, it is the
+ * pool for allocations.
+ */
+
+#include <stdlib.h>
+uint8_t ao_scheme_const[AO_SCHEME_POOL_CONST] __attribute__((aligned(4)));
+#define ao_scheme_pool ao_scheme_const
+#undef AO_SCHEME_POOL
+#define AO_SCHEME_POOL AO_SCHEME_POOL_CONST
+
+#else
+
+uint8_t	ao_scheme_pool[AO_SCHEME_POOL + AO_SCHEME_POOL_EXTRA] __attribute__((aligned(4)));
+
+#endif
+
+#ifndef DBG_MEM_STATS
+#define DBG_MEM_STATS	DBG_MEM
+#endif
+
+#if DBG_MEM
+int dbg_move_depth;
+int dbg_mem = DBG_MEM_START;
+int dbg_validate = 0;
+
+struct ao_scheme_record {
+	struct ao_scheme_record		*next;
+	const struct ao_scheme_type	*type;
+	void				*addr;
+	int				size;
+};
+
+static struct ao_scheme_record	*record_head, **record_tail;
+
+static void
+ao_scheme_record_free(struct ao_scheme_record *record)
+{
+	while (record) {
+		struct ao_scheme_record *next = record->next;
+		free(record);
+		record = next;
+	}
+}
+
+static void
+ao_scheme_record_reset(void)
+{
+	ao_scheme_record_free(record_head);
+	record_head = NULL;
+	record_tail = &record_head;
+}
+
+static void
+ao_scheme_record(const struct ao_scheme_type	*type,
+	       void				*addr,
+	       int				size)
+{
+	struct ao_scheme_record	*r = malloc(sizeof (struct ao_scheme_record));
+
+	r->next = NULL;
+	r->type = type;
+	r->addr = addr;
+	r->size = size;
+	*record_tail = r;
+	record_tail = &r->next;
+}
+
+static struct ao_scheme_record *
+ao_scheme_record_save(void)
+{
+	struct ao_scheme_record *r = record_head;
+
+	record_head = NULL;
+	record_tail = &record_head;
+	return r;
+}
+
+static void
+ao_scheme_record_compare(char *where,
+		       struct ao_scheme_record *a,
+		       struct ao_scheme_record *b)
+{
+	while (a && b) {
+		if (a->type != b->type || a->size != b->size) {
+			printf("%s record difers %d %s %d -> %d %s %d\n",
+			       where,
+			       MDBG_OFFSET(a->addr),
+			       a->type->name,
+			       a->size,
+			       MDBG_OFFSET(b->addr),
+			       b->type->name,
+			       b->size);
+			ao_scheme_abort();
+		}
+		a = a->next;
+		b = b->next;
+	}
+	if (a) {
+		printf("%s record differs %d %s %d -> NULL\n",
+		       where,
+		       MDBG_OFFSET(a->addr),
+		       a->type->name,
+		       a->size);
+		ao_scheme_abort();
+	}
+	if (b) {
+		printf("%s record differs NULL -> %d %s %d\n",
+		       where,
+		       MDBG_OFFSET(b->addr),
+		       b->type->name,
+		       b->size);
+		ao_scheme_abort();
+	}
+}
+
+#else
+#define ao_scheme_record_reset()
+#endif
+
+uint8_t	ao_scheme_exception;
+
+struct ao_scheme_root {
+	const struct ao_scheme_type	*type;
+	void				**addr;
+};
+
+static struct ao_scheme_cons 	*save_cons[2];
+static char			*save_string[2];
+static struct ao_scheme_frame	*save_frame[1];
+static ao_poly			save_poly[3];
+
+static const struct ao_scheme_root	ao_scheme_root[] = {
+	{
+		.type = &ao_scheme_cons_type,
+		.addr = (void **) &save_cons[0],
+	},
+	{
+		.type = &ao_scheme_cons_type,
+		.addr = (void **) &save_cons[1],
+	},
+	{
+		.type = &ao_scheme_string_type,
+		.addr = (void **) &save_string[0],
+	},
+	{
+		.type = &ao_scheme_string_type,
+		.addr = (void **) &save_string[1],
+	},
+	{
+		.type = &ao_scheme_frame_type,
+		.addr = (void **) &save_frame[0],
+	},
+	{
+		.type = NULL,
+		.addr = (void **) (void *) &save_poly[0]
+	},
+	{
+		.type = NULL,
+		.addr = (void **) (void *) &save_poly[1]
+	},
+	{
+		.type = NULL,
+		.addr = (void **) (void *) &save_poly[2]
+	},
+	{
+		.type = &ao_scheme_atom_type,
+		.addr = (void **) &ao_scheme_atoms
+	},
+	{
+		.type = &ao_scheme_frame_type,
+		.addr = (void **) &ao_scheme_frame_global,
+	},
+	{
+		.type = &ao_scheme_frame_type,
+		.addr = (void **) &ao_scheme_frame_current,
+	},
+	{
+		.type = &ao_scheme_stack_type,
+		.addr = (void **) &ao_scheme_stack,
+	},
+	{
+		.type = NULL,
+		.addr = (void **) (void *) &ao_scheme_v,
+	},
+	{
+		.type = &ao_scheme_cons_type,
+		.addr = (void **) &ao_scheme_read_cons,
+	},
+	{
+		.type = &ao_scheme_cons_type,
+		.addr = (void **) &ao_scheme_read_cons_tail,
+	},
+	{
+		.type = &ao_scheme_cons_type,
+		.addr = (void **) &ao_scheme_read_stack,
+	},
+#ifdef AO_SCHEME_MAKE_CONST
+	{
+		.type = &ao_scheme_bool_type,
+		.addr = (void **) &ao_scheme_false,
+	},
+	{
+		.type = &ao_scheme_bool_type,
+		.addr = (void **) &ao_scheme_true,
+	},
+#endif
+};
+
+#define AO_SCHEME_ROOT	(sizeof (ao_scheme_root) / sizeof (ao_scheme_root[0]))
+
+static const void ** const ao_scheme_cache[] = {
+	(const void **) &ao_scheme_cons_free_list,
+	(const void **) &ao_scheme_stack_free_list,
+	(const void **) &ao_scheme_frame_free_list[0],
+	(const void **) &ao_scheme_frame_free_list[1],
+	(const void **) &ao_scheme_frame_free_list[2],
+	(const void **) &ao_scheme_frame_free_list[3],
+	(const void **) &ao_scheme_frame_free_list[4],
+	(const void **) &ao_scheme_frame_free_list[5],
+};
+
+#if AO_SCHEME_FRAME_FREE != 6
+#error Unexpected AO_SCHEME_FRAME_FREE value
+#endif
+
+#define AO_SCHEME_CACHE	(sizeof (ao_scheme_cache) / sizeof (ao_scheme_cache[0]))
+
+#define AO_SCHEME_BUSY_SIZE	((AO_SCHEME_POOL + 31) / 32)
+
+static uint8_t	ao_scheme_busy[AO_SCHEME_BUSY_SIZE];
+static uint8_t	ao_scheme_cons_note[AO_SCHEME_BUSY_SIZE];
+static uint8_t	ao_scheme_cons_last[AO_SCHEME_BUSY_SIZE];
+static uint8_t	ao_scheme_cons_noted;
+
+uint16_t	ao_scheme_top;
+
+struct ao_scheme_chunk {
+	uint16_t		old_offset;
+	union {
+		uint16_t	size;
+		uint16_t	new_offset;
+	};
+};
+
+#define AO_SCHEME_NCHUNK	64
+
+static struct ao_scheme_chunk ao_scheme_chunk[AO_SCHEME_NCHUNK];
+
+/* Offset of an address within the pool. */
+static inline uint16_t pool_offset(void *addr) {
+#if DBG_MEM
+	if (!AO_SCHEME_IS_POOL(addr))
+		ao_scheme_abort();
+#endif
+	return ((uint8_t *) addr) - ao_scheme_pool;
+}
+
+static inline void mark(uint8_t *tag, int offset) {
+	int	byte = offset >> 5;
+	int	bit = (offset >> 2) & 7;
+	tag[byte] |= (1 << bit);
+}
+
+static inline void clear(uint8_t *tag, int offset) {
+	int	byte = offset >> 5;
+	int	bit = (offset >> 2) & 7;
+	tag[byte] &= ~(1 << bit);
+}
+
+static inline int busy(uint8_t *tag, int offset) {
+	int	byte = offset >> 5;
+	int	bit = (offset >> 2) & 7;
+	return (tag[byte] >> bit) & 1;
+}
+
+static inline int min(int a, int b) { return a < b ? a : b; }
+static inline int max(int a, int b) { return a > b ? a : b; }
+
+static inline int limit(int offset) {
+	return min(AO_SCHEME_POOL, max(offset, 0));
+}
+
+static void
+note_cons(uint16_t offset)
+{
+	MDBG_MOVE("note cons %d\n", offset);
+	ao_scheme_cons_noted = 1;
+	mark(ao_scheme_cons_note, offset);
+}
+
+static uint16_t	chunk_low, chunk_high;
+static uint16_t	chunk_first, chunk_last;
+
+static int
+find_chunk(uint16_t offset)
+{
+	int l, r;
+	/* Binary search for the location */
+	l = chunk_first;
+	r = chunk_last - 1;
+	while (l <= r) {
+		int m = (l + r) >> 1;
+		if (ao_scheme_chunk[m].old_offset < offset)
+			l = m + 1;
+		else
+			r = m - 1;
+	}
+	return l;
+}
+
+static void
+note_chunk(uint16_t offset, uint16_t size)
+{
+	int l;
+
+	if (offset < chunk_low || chunk_high <= offset)
+		return;
+
+	l = find_chunk(offset);
+
+	/*
+	 * The correct location is always in 'l', with r = l-1 being
+	 * the entry before the right one
+	 */
+
+#if DBG_MEM
+	/* Off the right side */
+	if (l >= AO_SCHEME_NCHUNK)
+		ao_scheme_abort();
+
+	/* Off the left side */
+	if (l == 0 && chunk_last && offset > ao_scheme_chunk[0].old_offset)
+		ao_scheme_abort();
+#endif
+
+	/* Shuffle existing entries right */
+	int end = min(AO_SCHEME_NCHUNK, chunk_last + 1);
+
+	memmove(&ao_scheme_chunk[l+1],
+		&ao_scheme_chunk[l],
+		(end - (l+1)) * sizeof (struct ao_scheme_chunk));
+
+	/* Add new entry */
+	ao_scheme_chunk[l].old_offset = offset;
+	ao_scheme_chunk[l].size = size;
+
+	/* Increment the number of elements up to the size of the array */
+	if (chunk_last < AO_SCHEME_NCHUNK)
+		chunk_last++;
+
+	/* Set the top address if the array is full */
+	if (chunk_last == AO_SCHEME_NCHUNK)
+		chunk_high = ao_scheme_chunk[AO_SCHEME_NCHUNK-1].old_offset +
+			ao_scheme_chunk[AO_SCHEME_NCHUNK-1].size;
+}
+
+static void
+reset_chunks(void)
+{
+	chunk_high = ao_scheme_top;
+	chunk_last = 0;
+	chunk_first = 0;
+}
+
+/*
+ * Walk all referenced objects calling functions on each one
+ */
+
+static void
+walk(int (*visit_addr)(const struct ao_scheme_type *type, void **addr),
+     int (*visit_poly)(ao_poly *p, uint8_t do_note_cons))
+{
+	int i;
+
+	ao_scheme_record_reset();
+	memset(ao_scheme_busy, '\0', sizeof (ao_scheme_busy));
+	memset(ao_scheme_cons_note, '\0', sizeof (ao_scheme_cons_note));
+	ao_scheme_cons_noted = 0;
+	for (i = 0; i < (int) AO_SCHEME_ROOT; i++) {
+		if (ao_scheme_root[i].type) {
+			void **a = ao_scheme_root[i].addr, *v;
+			if (a && (v = *a)) {
+				MDBG_MOVE("root ptr %d\n", MDBG_OFFSET(v));
+				visit_addr(ao_scheme_root[i].type, a);
+			}
+		} else {
+			ao_poly *a = (ao_poly *) ao_scheme_root[i].addr, p;
+			if (a && (p = *a)) {
+				MDBG_MOVE("root poly %d\n", MDBG_OFFSET(ao_scheme_ref(p)));
+				visit_poly(a, 0);
+			}
+		}
+	}
+	while (ao_scheme_cons_noted) {
+		memcpy(ao_scheme_cons_last, ao_scheme_cons_note, sizeof (ao_scheme_cons_note));
+		memset(ao_scheme_cons_note, '\0', sizeof (ao_scheme_cons_note));
+		ao_scheme_cons_noted = 0;
+		for (i = 0; i < AO_SCHEME_POOL; i += 4) {
+			if (busy(ao_scheme_cons_last, i)) {
+				void *v = ao_scheme_pool + i;
+				MDBG_MOVE("root cons %d\n", MDBG_OFFSET(v));
+				visit_addr(&ao_scheme_cons_type, &v);
+			}
+		}
+	}
+}
+
+#if MDBG_DUMP
+static void
+dump_busy(void)
+{
+	int	i;
+	MDBG_MOVE("busy:");
+	for (i = 0; i < ao_scheme_top; i += 4) {
+		if ((i & 0xff) == 0) {
+			MDBG_MORE("\n");
+			MDBG_MOVE("%s", "");
+		}
+		else if ((i & 0x1f) == 0)
+			MDBG_MORE(" ");
+		if (busy(ao_scheme_busy, i))
+			MDBG_MORE("*");
+		else
+			MDBG_MORE("-");
+	}
+	MDBG_MORE ("\n");
+}
+#define DUMP_BUSY()	dump_busy()
+#else
+#define DUMP_BUSY()
+#endif
+
+static const struct ao_scheme_type * const ao_scheme_types[AO_SCHEME_NUM_TYPE] = {
+	[AO_SCHEME_CONS] = &ao_scheme_cons_type,
+	[AO_SCHEME_INT] = NULL,
+	[AO_SCHEME_STRING] = &ao_scheme_string_type,
+	[AO_SCHEME_OTHER] = (void *) 0x1,
+	[AO_SCHEME_ATOM] = &ao_scheme_atom_type,
+	[AO_SCHEME_BUILTIN] = &ao_scheme_builtin_type,
+	[AO_SCHEME_FRAME] = &ao_scheme_frame_type,
+	[AO_SCHEME_FRAME_VALS] = &ao_scheme_frame_vals_type,
+	[AO_SCHEME_LAMBDA] = &ao_scheme_lambda_type,
+	[AO_SCHEME_STACK] = &ao_scheme_stack_type,
+	[AO_SCHEME_BOOL] = &ao_scheme_bool_type,
+	[AO_SCHEME_BIGINT] = &ao_scheme_bigint_type,
+	[AO_SCHEME_FLOAT] = &ao_scheme_float_type,
+};
+
+static int
+ao_scheme_mark_ref(const struct ao_scheme_type *type, void **ref)
+{
+	return ao_scheme_mark(type, *ref);
+}
+
+static int
+ao_scheme_poly_mark_ref(ao_poly *p, uint8_t do_note_cons)
+{
+	return ao_scheme_poly_mark(*p, do_note_cons);
+}
+
+#if DBG_MEM_STATS
+int ao_scheme_collects[2];
+int ao_scheme_freed[2];
+int ao_scheme_loops[2];
+#endif
+
+int ao_scheme_last_top;
+
+int
+ao_scheme_collect(uint8_t style)
+{
+	int	i;
+	int	top;
+#if DBG_MEM_STATS
+	int	loops = 0;
+#endif
+#if DBG_MEM
+	struct ao_scheme_record	*mark_record = NULL, *move_record = NULL;
+
+	MDBG_MOVE("collect %d\n", ao_scheme_collects[style]);
+#endif
+	MDBG_DO(ao_scheme_frame_write(ao_scheme_frame_poly(ao_scheme_frame_global)));
+
+	/* The first time through, we're doing a full collect */
+	if (ao_scheme_last_top == 0)
+		style = AO_SCHEME_COLLECT_FULL;
+
+	/* Clear references to all caches */
+	for (i = 0; i < (int) AO_SCHEME_CACHE; i++)
+		*ao_scheme_cache[i] = NULL;
+	if (style == AO_SCHEME_COLLECT_FULL) {
+		chunk_low = top = 0;
+	} else {
+		chunk_low = top = ao_scheme_last_top;
+	}
+	for (;;) {
+#if DBG_MEM_STATS
+		loops++;
+#endif
+		MDBG_MOVE("move chunks from %d to %d\n", chunk_low, top);
+		/* Find the sizes of the first chunk of objects to move */
+		reset_chunks();
+		walk(ao_scheme_mark_ref, ao_scheme_poly_mark_ref);
+#if DBG_MEM
+
+		ao_scheme_record_free(mark_record);
+		mark_record = ao_scheme_record_save();
+		if (mark_record && move_record)
+			ao_scheme_record_compare("mark", move_record, mark_record);
+#endif
+
+		DUMP_BUSY();
+
+		/* Find the first moving object */
+		for (i = 0; i < chunk_last; i++) {
+			uint16_t	size = ao_scheme_chunk[i].size;
+
+#if DBG_MEM
+			if (!size)
+				ao_scheme_abort();
+#endif
+
+			if (ao_scheme_chunk[i].old_offset > top)
+				break;
+
+			MDBG_MOVE("chunk %d %d not moving\n",
+				  ao_scheme_chunk[i].old_offset,
+				  ao_scheme_chunk[i].size);
+#if DBG_MEM
+			if (ao_scheme_chunk[i].old_offset != top)
+				ao_scheme_abort();
+#endif
+			top += size;
+		}
+
+		/*
+		 * Limit amount of chunk array used in mapping moves
+		 * to the active region
+		 */
+		chunk_first = i;
+		chunk_low = ao_scheme_chunk[i].old_offset;
+
+		/* Copy all of the objects */
+		for (; i < chunk_last; i++) {
+			uint16_t	size = ao_scheme_chunk[i].size;
+
+#if DBG_MEM
+			if (!size)
+				ao_scheme_abort();
+#endif
+
+			MDBG_MOVE("chunk %d %d -> %d\n",
+				  ao_scheme_chunk[i].old_offset,
+				  size,
+				  top);
+			ao_scheme_chunk[i].new_offset = top;
+
+			memmove(&ao_scheme_pool[top],
+				&ao_scheme_pool[ao_scheme_chunk[i].old_offset],
+				size);
+
+			top += size;
+		}
+
+		if (chunk_first < chunk_last) {
+			/* Relocate all references to the objects */
+			walk(ao_scheme_move, ao_scheme_poly_move);
+
+#if DBG_MEM
+			ao_scheme_record_free(move_record);
+			move_record = ao_scheme_record_save();
+			if (mark_record && move_record)
+				ao_scheme_record_compare("move", mark_record, move_record);
+#endif
+		}
+
+		/* If we ran into the end of the heap, then
+		 * there's no need to keep walking
+		 */
+		if (chunk_last != AO_SCHEME_NCHUNK)
+			break;
+
+		/* Next loop starts right above this loop */
+		chunk_low = chunk_high;
+	}
+
+#if DBG_MEM_STATS
+	/* Collect stats */
+	++ao_scheme_collects[style];
+	ao_scheme_freed[style] += ao_scheme_top - top;
+	ao_scheme_loops[style] += loops;
+#endif
+
+	ao_scheme_top = top;
+	if (style == AO_SCHEME_COLLECT_FULL)
+		ao_scheme_last_top = top;
+
+	MDBG_DO(memset(ao_scheme_chunk, '\0', sizeof (ao_scheme_chunk));
+		walk(ao_scheme_mark_ref, ao_scheme_poly_mark_ref));
+
+	return AO_SCHEME_POOL - ao_scheme_top;
+}
+
+#if DBG_FREE_CONS
+void
+ao_scheme_cons_check(struct ao_scheme_cons *cons)
+{
+	ao_poly	cdr;
+	int offset;
+
+	chunk_low = 0;
+	reset_chunks();
+	walk(ao_scheme_mark_ref, ao_scheme_poly_mark_ref);
+	while (cons) {
+		if (!AO_SCHEME_IS_POOL(cons))
+			break;
+		offset = pool_offset(cons);
+		if (busy(ao_scheme_busy, offset)) {
+			ao_scheme_printf("cons at %p offset %d poly %d is busy\n\t%v\n", cons, offset, ao_scheme_cons_poly(cons), ao_scheme_cons_poly(cons));
+			abort();
+		}
+		cdr = cons->cdr;
+		if (!ao_scheme_is_pair(cdr))
+			break;
+		cons = ao_scheme_poly_cons(cdr);
+	}
+}
+#endif
+
+/*
+ * Mark interfaces for objects
+ */
+
+
+/*
+ * Mark a block of memory with an explicit size
+ */
+
+int
+ao_scheme_mark_block(void *addr, int size)
+{
+	int offset;
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	offset = pool_offset(addr);
+	MDBG_MOVE("mark memory %d\n", MDBG_OFFSET(addr));
+	if (busy(ao_scheme_busy, offset)) {
+		MDBG_MOVE("already marked\n");
+		return 1;
+	}
+	mark(ao_scheme_busy, offset);
+	note_chunk(offset, size);
+	return 0;
+}
+
+/*
+ * Note a reference to memory and collect information about a few
+ * object sizes at a time
+ */
+
+int
+ao_scheme_mark_memory(const struct ao_scheme_type *type, void *addr)
+{
+	int offset;
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	offset = pool_offset(addr);
+	MDBG_MOVE("mark memory %d\n", MDBG_OFFSET(addr));
+	if (busy(ao_scheme_busy, offset)) {
+		MDBG_MOVE("already marked\n");
+		return 1;
+	}
+	mark(ao_scheme_busy, offset);
+	note_chunk(offset, ao_scheme_size(type, addr));
+	return 0;
+}
+
+/*
+ * Mark an object and all that it refereces
+ */
+int
+ao_scheme_mark(const struct ao_scheme_type *type, void *addr)
+{
+	int ret;
+	MDBG_MOVE("mark %d\n", MDBG_OFFSET(addr));
+	MDBG_MOVE_IN();
+	ret = ao_scheme_mark_memory(type, addr);
+	if (!ret) {
+		MDBG_MOVE("mark recurse\n");
+		type->mark(addr);
+	}
+	MDBG_MOVE_OUT();
+	return ret;
+}
+
+/*
+ * Mark an object, unless it is a cons cell and
+ * do_note_cons is set. In that case, just
+ * set a bit in the cons note array; those
+ * will be marked in a separate pass to avoid
+ * deep recursion in the collector
+ */
+int
+ao_scheme_poly_mark(ao_poly p, uint8_t do_note_cons)
+{
+	uint8_t type;
+	void	*addr;
+
+	type = ao_scheme_poly_base_type(p);
+
+	if (type == AO_SCHEME_INT)
+		return 1;
+
+	addr = ao_scheme_ref(p);
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	if (type == AO_SCHEME_CONS && do_note_cons) {
+		note_cons(pool_offset(addr));
+		return 1;
+	} else {
+		if (type == AO_SCHEME_OTHER)
+			type = ao_scheme_other_type(addr);
+
+		const struct ao_scheme_type *lisp_type = ao_scheme_types[type];
+#if DBG_MEM
+		if (!lisp_type)
+			ao_scheme_abort();
+#endif
+
+		return ao_scheme_mark(lisp_type, addr);
+	}
+}
+
+/*
+ * Find the current location of an object
+ * based on the original location. For unmoved
+ * objects, this is simple. For moved objects,
+ * go search for it
+ */
+
+static uint16_t
+move_map(uint16_t offset)
+{
+	int		l;
+
+	if (offset < chunk_low || chunk_high <= offset)
+		return offset;
+
+	l = find_chunk(offset);
+
+#if DBG_MEM
+	if (ao_scheme_chunk[l].old_offset != offset)
+		ao_scheme_abort();
+#endif
+	return ao_scheme_chunk[l].new_offset;
+}
+
+int
+ao_scheme_move_memory(const struct ao_scheme_type *type, void **ref)
+{
+	void		*addr = *ref;
+	uint16_t	offset, orig_offset;
+
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	(void) type;
+
+	MDBG_MOVE("move memory %d\n", MDBG_OFFSET(addr));
+	orig_offset = pool_offset(addr);
+	offset = move_map(orig_offset);
+	if (offset != orig_offset) {
+		MDBG_MOVE("update ref %d %d -> %d\n",
+			  AO_SCHEME_IS_POOL(ref) ? MDBG_OFFSET(ref) : -1,
+			  orig_offset, offset);
+		*ref = ao_scheme_pool + offset;
+	}
+	if (busy(ao_scheme_busy, offset)) {
+		MDBG_MOVE("already moved\n");
+		return 1;
+	}
+	mark(ao_scheme_busy, offset);
+	MDBG_DO(ao_scheme_record(type, addr, ao_scheme_size(type, addr)));
+	return 0;
+}
+
+int
+ao_scheme_move(const struct ao_scheme_type *type, void **ref)
+{
+	int ret;
+	MDBG_MOVE("move object %d\n", MDBG_OFFSET(*ref));
+	MDBG_MOVE_IN();
+	ret = ao_scheme_move_memory(type, ref);
+	if (!ret) {
+		MDBG_MOVE("move recurse\n");
+		type->move(*ref);
+	}
+	MDBG_MOVE_OUT();
+	return ret;
+}
+
+int
+ao_scheme_poly_move(ao_poly *ref, uint8_t do_note_cons)
+{
+	uint8_t		type;
+	ao_poly		p = *ref;
+	int		ret;
+	void		*addr;
+	uint16_t	offset, orig_offset;
+	uint8_t		base_type;
+
+	base_type = type = ao_scheme_poly_base_type(p);
+
+	if (type == AO_SCHEME_INT)
+		return 1;
+
+	addr = ao_scheme_ref(p);
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	orig_offset = pool_offset(addr);
+	offset = move_map(orig_offset);
+
+	if (type == AO_SCHEME_CONS && do_note_cons) {
+		note_cons(orig_offset);
+		ret = 1;
+	} else {
+		if (type == AO_SCHEME_OTHER)
+			type = ao_scheme_other_type(ao_scheme_pool + offset);
+
+		const struct ao_scheme_type *lisp_type = ao_scheme_types[type];
+#if DBG_MEM
+		if (!lisp_type)
+			ao_scheme_abort();
+#endif
+
+		ret = ao_scheme_move(lisp_type, &addr);
+	}
+
+	/* Re-write the poly value */
+	if (offset != orig_offset) {
+		ao_poly np = ao_scheme_poly(ao_scheme_pool + offset, base_type);
+		MDBG_MOVE("poly %d moved %d -> %d\n",
+			  type, orig_offset, offset);
+		*ref = np;
+	}
+	return ret;
+}
+
+#if DBG_MEM
+void
+ao_scheme_validate(void)
+{
+	chunk_low = 0;
+	memset(ao_scheme_chunk, '\0', sizeof (ao_scheme_chunk));
+	walk(ao_scheme_mark_ref, ao_scheme_poly_mark_ref);
+}
+
+int dbg_allocs;
+
+#endif
+
+void *
+ao_scheme_alloc(int size)
+{
+	void	*addr;
+
+	MDBG_DO(++dbg_allocs);
+	MDBG_DO(if (dbg_validate) ao_scheme_validate());
+	size = ao_scheme_size_round(size);
+	if (AO_SCHEME_POOL - ao_scheme_top < size &&
+	    ao_scheme_collect(AO_SCHEME_COLLECT_INCREMENTAL) < size &&
+	    ao_scheme_collect(AO_SCHEME_COLLECT_FULL) < size)
+	{
+		ao_scheme_error(AO_SCHEME_OOM, "out of memory");
+		return NULL;
+	}
+	addr = ao_scheme_pool + ao_scheme_top;
+	ao_scheme_top += size;
+	MDBG_MOVE("alloc %d size %d\n", MDBG_OFFSET(addr), size);
+	return addr;
+}
+
+void
+ao_scheme_cons_stash(int id, struct ao_scheme_cons *cons)
+{
+	assert(save_cons[id] == 0);
+	save_cons[id] = cons;
+}
+
+struct ao_scheme_cons *
+ao_scheme_cons_fetch(int id)
+{
+	struct ao_scheme_cons *cons = save_cons[id];
+	save_cons[id] = NULL;
+	return cons;
+}
+
+void
+ao_scheme_poly_stash(int id, ao_poly poly)
+{
+	assert(save_poly[id] == AO_SCHEME_NIL);
+	save_poly[id] = poly;
+}
+
+ao_poly
+ao_scheme_poly_fetch(int id)
+{
+	ao_poly poly = save_poly[id];
+	save_poly[id] = AO_SCHEME_NIL;
+	return poly;
+}
+
+void
+ao_scheme_string_stash(int id, char *string)
+{
+	assert(save_string[id] == NULL);
+	save_string[id] = string;
+}
+
+char *
+ao_scheme_string_fetch(int id)
+{
+	char *string = save_string[id];
+	save_string[id] = NULL;
+	return string;
+}
+
+void
+ao_scheme_frame_stash(int id, struct ao_scheme_frame *frame)
+{
+	assert(save_frame[id] == NULL);
+	save_frame[id] = frame;
+}
+
+struct ao_scheme_frame *
+ao_scheme_frame_fetch(int id)
+{
+	struct ao_scheme_frame *frame = save_frame[id];
+	save_frame[id] = NULL;
+	return frame;
+}
diff --git a/src/scheme/ao_scheme_poly.c b/src/scheme/ao_scheme_poly.c
new file mode 100644
index 00000000..d726321c
--- /dev/null
+++ b/src/scheme/ao_scheme_poly.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+struct ao_scheme_funcs {
+	void (*write)(ao_poly);
+	void (*display)(ao_poly);
+};
+
+static const struct ao_scheme_funcs ao_scheme_funcs[AO_SCHEME_NUM_TYPE] = {
+	[AO_SCHEME_CONS] = {
+		.write = ao_scheme_cons_write,
+		.display = ao_scheme_cons_display,
+	},
+	[AO_SCHEME_STRING] = {
+		.write = ao_scheme_string_write,
+		.display = ao_scheme_string_display,
+	},
+	[AO_SCHEME_INT] = {
+		.write = ao_scheme_int_write,
+		.display = ao_scheme_int_write,
+	},
+	[AO_SCHEME_ATOM] = {
+		.write = ao_scheme_atom_write,
+		.display = ao_scheme_atom_write,
+	},
+	[AO_SCHEME_BUILTIN] = {
+		.write = ao_scheme_builtin_write,
+		.display = ao_scheme_builtin_write,
+	},
+	[AO_SCHEME_FRAME] = {
+		.write = ao_scheme_frame_write,
+		.display = ao_scheme_frame_write,
+	},
+	[AO_SCHEME_FRAME_VALS] = {
+		.write = NULL,
+		.display = NULL,
+	},
+	[AO_SCHEME_LAMBDA] = {
+		.write = ao_scheme_lambda_write,
+		.display = ao_scheme_lambda_write,
+	},
+	[AO_SCHEME_STACK] = {
+		.write = ao_scheme_stack_write,
+		.display = ao_scheme_stack_write,
+	},
+	[AO_SCHEME_BOOL] = {
+		.write = ao_scheme_bool_write,
+		.display = ao_scheme_bool_write,
+	},
+	[AO_SCHEME_BIGINT] = {
+		.write = ao_scheme_bigint_write,
+		.display = ao_scheme_bigint_write,
+	},
+	[AO_SCHEME_FLOAT] = {
+		.write = ao_scheme_float_write,
+		.display = ao_scheme_float_write,
+	},
+};
+
+static const struct ao_scheme_funcs *
+funcs(ao_poly p)
+{
+	uint8_t	type = ao_scheme_poly_type(p);
+
+	if (type < AO_SCHEME_NUM_TYPE)
+		return &ao_scheme_funcs[type];
+	return NULL;
+}
+
+void
+ao_scheme_poly_write(ao_poly p)
+{
+	const struct ao_scheme_funcs *f = funcs(p);
+
+	if (f && f->write)
+		f->write(p);
+}
+
+void
+ao_scheme_poly_display(ao_poly p)
+{
+	const struct ao_scheme_funcs *f = funcs(p);
+
+	if (f && f->display)
+		f->display(p);
+}
+
+void *
+ao_scheme_ref(ao_poly poly) {
+	if (poly == AO_SCHEME_NIL)
+		return NULL;
+	if (poly & AO_SCHEME_CONST)
+		return (void *) (ao_scheme_const + (poly & AO_SCHEME_REF_MASK) - 4);
+	return (void *) (ao_scheme_pool + (poly & AO_SCHEME_REF_MASK) - 4);
+}
+
+ao_poly
+ao_scheme_poly(const void *addr, ao_poly type) {
+	const uint8_t	*a = addr;
+	if (a == NULL)
+		return AO_SCHEME_NIL;
+	if (AO_SCHEME_IS_CONST(a))
+		return AO_SCHEME_CONST | (a - ao_scheme_const + 4) | type;
+	return (a - ao_scheme_pool + 4) | type;
+}
diff --git a/src/scheme/ao_scheme_read.c b/src/scheme/ao_scheme_read.c
new file mode 100644
index 00000000..6b1e9d66
--- /dev/null
+++ b/src/scheme/ao_scheme_read.c
@@ -0,0 +1,655 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include "ao_scheme_read.h"
+#include <math.h>
+#include <stdlib.h>
+
+static const uint16_t	lex_classes[128] = {
+	IGNORE,		/* ^@ */
+	IGNORE,		/* ^A */
+	IGNORE,		/* ^B */
+	IGNORE,		/* ^C */
+	IGNORE,		/* ^D */
+	IGNORE,		/* ^E */
+	IGNORE,		/* ^F */
+	IGNORE,		/* ^G */
+	IGNORE,		/* ^H */
+	WHITE,		/* ^I */
+	WHITE,		/* ^J */
+	WHITE,		/* ^K */
+	WHITE,		/* ^L */
+	WHITE,		/* ^M */
+	IGNORE,		/* ^N */
+	IGNORE,		/* ^O */
+	IGNORE,		/* ^P */
+	IGNORE,		/* ^Q */
+	IGNORE,		/* ^R */
+	IGNORE,		/* ^S */
+	IGNORE,		/* ^T */
+	IGNORE,		/* ^U */
+	IGNORE,		/* ^V */
+	IGNORE,		/* ^W */
+	IGNORE,		/* ^X */
+	IGNORE,		/* ^Y */
+	IGNORE,		/* ^Z */
+	IGNORE,		/* ^[ */
+	IGNORE,		/* ^\ */
+	IGNORE,		/* ^] */
+	IGNORE,		/* ^^ */
+	IGNORE,		/* ^_ */
+	PRINTABLE|WHITE,	/*    */
+ 	PRINTABLE,		/* ! */
+ 	PRINTABLE|STRINGC,	/* " */
+ 	PRINTABLE|POUND,	/* # */
+ 	PRINTABLE,		/* $ */
+ 	PRINTABLE,		/* % */
+ 	PRINTABLE,		/* & */
+ 	PRINTABLE|SPECIAL,	/* ' */
+ 	PRINTABLE|SPECIAL,	/* ( */
+ 	PRINTABLE|SPECIAL,	/* ) */
+ 	PRINTABLE,		/* * */
+ 	PRINTABLE|SIGN,		/* + */
+ 	PRINTABLE|SPECIAL,	/* , */
+ 	PRINTABLE|SIGN,		/* - */
+ 	PRINTABLE|DOTC|FLOATC,	/* . */
+ 	PRINTABLE,		/* / */
+ 	PRINTABLE|DIGIT,	/* 0 */
+ 	PRINTABLE|DIGIT,	/* 1 */
+ 	PRINTABLE|DIGIT,	/* 2 */
+ 	PRINTABLE|DIGIT,	/* 3 */
+ 	PRINTABLE|DIGIT,	/* 4 */
+ 	PRINTABLE|DIGIT,	/* 5 */
+ 	PRINTABLE|DIGIT,	/* 6 */
+ 	PRINTABLE|DIGIT,	/* 7 */
+ 	PRINTABLE|DIGIT,	/* 8 */
+ 	PRINTABLE|DIGIT,	/* 9 */
+ 	PRINTABLE,		/* : */
+ 	PRINTABLE|COMMENT,	/* ; */
+ 	PRINTABLE,		/* < */
+ 	PRINTABLE,		/* = */
+ 	PRINTABLE,		/* > */
+ 	PRINTABLE,		/* ? */
+  	PRINTABLE,		/*  @ */
+	PRINTABLE,		/*  A */
+	PRINTABLE,		/*  B */
+	PRINTABLE,		/*  C */
+	PRINTABLE,		/*  D */
+	PRINTABLE|FLOATC,	/*  E */
+	PRINTABLE,		/*  F */
+	PRINTABLE,		/*  G */
+	PRINTABLE,		/*  H */
+	PRINTABLE,		/*  I */
+	PRINTABLE,		/*  J */
+	PRINTABLE,		/*  K */
+	PRINTABLE,		/*  L */
+	PRINTABLE,		/*  M */
+	PRINTABLE,		/*  N */
+	PRINTABLE,		/*  O */
+	PRINTABLE,		/*  P */
+	PRINTABLE,		/*  Q */
+	PRINTABLE,		/*  R */
+	PRINTABLE,		/*  S */
+	PRINTABLE,		/*  T */
+	PRINTABLE,		/*  U */
+	PRINTABLE,		/*  V */
+	PRINTABLE,		/*  W */
+	PRINTABLE,		/*  X */
+	PRINTABLE,		/*  Y */
+	PRINTABLE,		/*  Z */
+	PRINTABLE,		/*  [ */
+	PRINTABLE|BACKSLASH,	/*  \ */
+	PRINTABLE,		/*  ] */
+	PRINTABLE,		/*  ^ */
+	PRINTABLE,		/*  _ */
+  	PRINTABLE|SPECIAL,	/*  ` */
+	PRINTABLE,		/*  a */
+	PRINTABLE,		/*  b */
+	PRINTABLE,		/*  c */
+	PRINTABLE,		/*  d */
+	PRINTABLE|FLOATC,	/*  e */
+	PRINTABLE,		/*  f */
+	PRINTABLE,		/*  g */
+	PRINTABLE,		/*  h */
+	PRINTABLE,		/*  i */
+	PRINTABLE,		/*  j */
+	PRINTABLE,		/*  k */
+	PRINTABLE,		/*  l */
+	PRINTABLE,		/*  m */
+	PRINTABLE,		/*  n */
+	PRINTABLE,		/*  o */
+	PRINTABLE,		/*  p */
+	PRINTABLE,		/*  q */
+	PRINTABLE,		/*  r */
+	PRINTABLE,		/*  s */
+	PRINTABLE,		/*  t */
+	PRINTABLE,		/*  u */
+	PRINTABLE,		/*  v */
+	PRINTABLE,		/*  w */
+	PRINTABLE,		/*  x */
+	PRINTABLE,		/*  y */
+	PRINTABLE,		/*  z */
+	PRINTABLE,		/*  { */
+	PRINTABLE,		/*  | */
+	PRINTABLE,		/*  } */
+	PRINTABLE,		/*  ~ */
+	IGNORE,			/*  ^? */
+};
+
+static int lex_unget_c;
+
+static inline int
+lex_get()
+{
+	int	c;
+	if (lex_unget_c) {
+		c = lex_unget_c;
+		lex_unget_c = 0;
+	} else {
+		c = ao_scheme_getc();
+	}
+	return c;
+}
+
+static inline void
+lex_unget(int c)
+{
+	if (c != EOF)
+		lex_unget_c = c;
+}
+
+static uint16_t	lex_class;
+
+static int
+lexc(void)
+{
+	int	c;
+	do {
+		c = lex_get();
+		if (c == EOF) {
+			c = 0;
+			lex_class = ENDOFFILE;
+		} else {
+			c &= 0x7f;
+			lex_class = lex_classes[c];
+		}
+	} while (lex_class & IGNORE);
+	return c;
+}
+
+static int
+lex_quoted(void)
+{
+	int	c;
+	int	v;
+	int	count;
+
+	c = lex_get();
+	if (c == EOF) {
+		lex_class = ENDOFFILE;
+		return 0;
+	}
+	lex_class = 0;
+	c &= 0x7f;
+ 	switch (c) {
+	case 'n':
+		return '\n';
+	case 'f':
+		return '\f';
+	case 'b':
+		return '\b';
+	case 'r':
+		return '\r';
+	case 'v':
+		return '\v';
+	case 't':
+		return '\t';
+	case '0':
+	case '1':
+	case '2':
+	case '3':
+	case '4':
+	case '5':
+	case '6':
+	case '7':
+		v = c - '0';
+		count = 1;
+		while (count <= 3) {
+			c = lex_get();
+			if (c == EOF)
+				return EOF;
+			c &= 0x7f;
+			if (c < '0' || '7' < c) {
+				lex_unget(c);
+				break;
+			}
+			v = (v << 3) + c - '0';
+			++count;
+		}
+		return v;
+	default:
+		return c;
+	}
+}
+
+#define AO_SCHEME_TOKEN_MAX	32
+
+static char	token_string[AO_SCHEME_TOKEN_MAX];
+static int32_t	token_int;
+static int	token_len;
+static float	token_float;
+
+static inline void add_token(int c) {
+	if (c && token_len < AO_SCHEME_TOKEN_MAX - 1)
+		token_string[token_len++] = c;
+}
+
+static inline void del_token(void) {
+	if (token_len > 0)
+		token_len--;
+}
+
+static inline void end_token(void) {
+	token_string[token_len] = '\0';
+}
+
+struct namedfloat {
+	const char	*name;
+	float		value;
+};
+
+static const struct namedfloat namedfloats[] = {
+	{ .name = "+inf.0", .value = INFINITY },
+	{ .name = "-inf.0", .value = -INFINITY },
+	{ .name = "+nan.0", .value = NAN },
+	{ .name = "-nan.0", .value = NAN },
+};
+
+#define NUM_NAMED_FLOATS	(sizeof namedfloats / sizeof namedfloats[0])
+
+static int
+_lex(void)
+{
+	int	c;
+
+	token_len = 0;
+	for (;;) {
+		c = lexc();
+		if (lex_class & ENDOFFILE)
+			return END;
+
+		if (lex_class & WHITE)
+			continue;
+
+		if (lex_class & COMMENT) {
+			while ((c = lexc()) != '\n') {
+				if (lex_class & ENDOFFILE)
+					return END;
+			}
+			continue;
+		}
+
+		if (lex_class & (SPECIAL|DOTC)) {
+			add_token(c);
+			end_token();
+			switch (c) {
+			case '(':
+			case '[':
+				return OPEN;
+			case ')':
+			case ']':
+				return CLOSE;
+			case '\'':
+				return QUOTE;
+			case '.':
+				return DOT;
+			case '`':
+				return QUASIQUOTE;
+			case ',':
+				c = lexc();
+				if (c == '@') {
+					add_token(c);
+					end_token();
+					return UNQUOTE_SPLICING;
+				} else {
+					lex_unget(c);
+					return UNQUOTE;
+				}
+			}
+		}
+		if (lex_class & POUND) {
+			c = lexc();
+			switch (c) {
+			case 't':
+				add_token(c);
+				end_token();
+				return BOOL;
+			case 'f':
+				add_token(c);
+				end_token();
+				return BOOL;
+			case '\\':
+				for (;;) {
+					int alphabetic;
+					c = lexc();
+					alphabetic = (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'));
+					if (token_len == 0) {
+						add_token(c);
+						if (!alphabetic)
+							break;
+					} else {
+						if (alphabetic)
+							add_token(c);
+						else {
+							lex_unget(c);
+							break;
+						}
+					}
+				}
+				end_token();
+				if (token_len == 1)
+					token_int = token_string[0];
+				else if (!strcmp(token_string, "space"))
+					token_int = ' ';
+				else if (!strcmp(token_string, "newline"))
+					token_int = '\n';
+				else if (!strcmp(token_string, "tab"))
+					token_int = '\t';
+				else if (!strcmp(token_string, "return"))
+					token_int = '\r';
+				else if (!strcmp(token_string, "formfeed"))
+					token_int = '\f';
+				else {
+					ao_scheme_error(AO_SCHEME_INVALID, "invalid character token #\\%s", token_string);
+					continue;
+				}
+				return NUM;
+			}
+		}
+		if (lex_class & STRINGC) {
+			for (;;) {
+				c = lexc();
+				if (lex_class & BACKSLASH)
+					c = lex_quoted();
+				if (lex_class & (STRINGC|ENDOFFILE)) {
+					end_token();
+					return STRING;
+				}
+				add_token(c);
+			}
+		}
+		if (lex_class & PRINTABLE) {
+			int	isfloat;
+			int	hasdigit;
+			int	isneg;
+			int	isint;
+			int	epos;
+
+			isfloat = 1;
+			isint = 1;
+			hasdigit = 0;
+			token_int = 0;
+			isneg = 0;
+			epos = 0;
+			for (;;) {
+				if (!(lex_class & NUMBER)) {
+					isint = 0;
+					isfloat = 0;
+				} else {
+					if (!(lex_class & INTEGER))
+						isint = 0;
+ 					if (token_len != epos &&
+					    (lex_class & SIGN))
+					{
+						isint = 0;
+						isfloat = 0;
+					}
+					if (c == '-')
+						isneg = 1;
+					if (c == '.' && epos != 0)
+						isfloat = 0;
+					if (c == 'e' || c == 'E') {
+						if (token_len == 0)
+							isfloat = 0;
+						else
+							epos = token_len + 1;
+					}
+					if (lex_class & DIGIT) {
+						hasdigit = 1;
+						if (isint)
+							token_int = token_int * 10 + c - '0';
+					}
+				}
+				add_token (c);
+				c = lexc ();
+				if ((lex_class & (NOTNAME)) && (c != '.' || !isfloat)) {
+					unsigned int u;
+//					if (lex_class & ENDOFFILE)
+//						clearerr (f);
+					lex_unget(c);
+					end_token ();
+					if (isint && hasdigit) {
+						if (isneg)
+							token_int = -token_int;
+						return NUM;
+					}
+					if (isfloat && hasdigit) {
+						token_float = strtof(token_string, NULL);
+						return FLOAT;
+					}
+					for (u = 0; u < NUM_NAMED_FLOATS; u++)
+						if (!strcmp(namedfloats[u].name, token_string)) {
+							token_float = namedfloats[u].value;
+							return FLOAT;
+						}
+					return NAME;
+				}
+			}
+		}
+	}
+}
+
+static inline int lex(void)
+{
+	int	parse_token = _lex();
+	RDBGI("token %d (%s)\n", parse_token, token_string);
+	return parse_token;
+}
+
+static int parse_token;
+
+struct ao_scheme_cons	*ao_scheme_read_cons;
+struct ao_scheme_cons	*ao_scheme_read_cons_tail;
+struct ao_scheme_cons	*ao_scheme_read_stack;
+
+#define READ_IN_QUOTE	0x01
+#define READ_SAW_DOT	0x02
+#define READ_DONE_DOT	0x04
+
+static int
+push_read_stack(int cons, int read_state)
+{
+	RDBGI("push read stack %p 0x%x\n", ao_scheme_read_cons, read_state);
+	RDBG_IN();
+	if (cons) {
+		ao_scheme_read_stack = ao_scheme_cons_cons(ao_scheme_cons_poly(ao_scheme_read_cons),
+						       ao_scheme__cons(ao_scheme_int_poly(read_state),
+								     ao_scheme_cons_poly(ao_scheme_read_stack)));
+		if (!ao_scheme_read_stack)
+			return 0;
+	}
+	ao_scheme_read_cons = NULL;
+	ao_scheme_read_cons_tail = NULL;
+	return 1;
+}
+
+static int
+pop_read_stack(int cons)
+{
+	int	read_state = 0;
+	if (cons) {
+		ao_scheme_read_cons = ao_scheme_poly_cons(ao_scheme_read_stack->car);
+		ao_scheme_read_stack = ao_scheme_poly_cons(ao_scheme_read_stack->cdr);
+		read_state = ao_scheme_poly_int(ao_scheme_read_stack->car);
+		ao_scheme_read_stack = ao_scheme_poly_cons(ao_scheme_read_stack->cdr);
+		for (ao_scheme_read_cons_tail = ao_scheme_read_cons;
+		     ao_scheme_read_cons_tail && ao_scheme_read_cons_tail->cdr;
+		     ao_scheme_read_cons_tail = ao_scheme_poly_cons(ao_scheme_read_cons_tail->cdr))
+			;
+	} else {
+		ao_scheme_read_cons = 0;
+		ao_scheme_read_cons_tail = 0;
+		ao_scheme_read_stack = 0;
+	}
+	RDBG_OUT();
+	RDBGI("pop read stack %p %d\n", ao_scheme_read_cons, read_state);
+	return read_state;
+}
+
+ao_poly
+ao_scheme_read(void)
+{
+	struct ao_scheme_atom	*atom;
+	char			*string;
+	int			cons;
+	int			read_state;
+	ao_poly			v = AO_SCHEME_NIL;
+
+	cons = 0;
+	read_state = 0;
+	ao_scheme_read_cons = ao_scheme_read_cons_tail = ao_scheme_read_stack = 0;
+	for (;;) {
+		parse_token = lex();
+		while (parse_token == OPEN) {
+			if (!push_read_stack(cons, read_state))
+				return AO_SCHEME_NIL;
+			cons++;
+			read_state = 0;
+			parse_token = lex();
+		}
+
+		switch (parse_token) {
+		case END:
+		default:
+			if (cons)
+				ao_scheme_error(AO_SCHEME_EOF, "unexpected end of file");
+			return _ao_scheme_atom_eof;
+			break;
+		case NAME:
+			atom = ao_scheme_atom_intern(token_string);
+			if (atom)
+				v = ao_scheme_atom_poly(atom);
+			else
+				v = AO_SCHEME_NIL;
+			break;
+		case NUM:
+			v = ao_scheme_integer_poly(token_int);
+			break;
+		case FLOAT:
+			v = ao_scheme_float_get(token_float);
+			break;
+		case BOOL:
+			if (token_string[0] == 't')
+				v = _ao_scheme_bool_true;
+			else
+				v = _ao_scheme_bool_false;
+			break;
+		case STRING:
+			string = ao_scheme_string_copy(token_string);
+			if (string)
+				v = ao_scheme_string_poly(string);
+			else
+				v = AO_SCHEME_NIL;
+			break;
+		case QUOTE:
+		case QUASIQUOTE:
+		case UNQUOTE:
+		case UNQUOTE_SPLICING:
+			if (!push_read_stack(cons, read_state))
+				return AO_SCHEME_NIL;
+			cons++;
+			read_state = READ_IN_QUOTE;
+			switch (parse_token) {
+			case QUOTE:
+				v = _ao_scheme_atom_quote;
+				break;
+			case QUASIQUOTE:
+				v = _ao_scheme_atom_quasiquote;
+				break;
+			case UNQUOTE:
+				v = _ao_scheme_atom_unquote;
+				break;
+			case UNQUOTE_SPLICING:
+				v = _ao_scheme_atom_unquote2dsplicing;
+				break;
+			}
+			break;
+		case CLOSE:
+			if (!cons) {
+				v = AO_SCHEME_NIL;
+				break;
+			}
+			v = ao_scheme_cons_poly(ao_scheme_read_cons);
+			--cons;
+			read_state = pop_read_stack(cons);
+			break;
+		case DOT:
+			if (!cons) {
+				ao_scheme_error(AO_SCHEME_INVALID, ". outside of cons");
+				return AO_SCHEME_NIL;
+			}
+			if (!ao_scheme_read_cons) {
+				ao_scheme_error(AO_SCHEME_INVALID, ". first in cons");
+				return AO_SCHEME_NIL;
+			}
+			read_state |= READ_SAW_DOT;
+			continue;
+		}
+
+		/* loop over QUOTE ends */
+		for (;;) {
+			if (!cons)
+				return v;
+
+			if (read_state & READ_DONE_DOT) {
+				ao_scheme_error(AO_SCHEME_INVALID, ". not last in cons");
+				return AO_SCHEME_NIL;
+			}
+
+			if (read_state & READ_SAW_DOT) {
+				read_state |= READ_DONE_DOT;
+				ao_scheme_read_cons_tail->cdr = v;
+			} else {
+				struct ao_scheme_cons	*read = ao_scheme_cons_cons(v, AO_SCHEME_NIL);
+				if (!read)
+					return AO_SCHEME_NIL;
+
+				if (ao_scheme_read_cons_tail)
+					ao_scheme_read_cons_tail->cdr = ao_scheme_cons_poly(read);
+				else
+					ao_scheme_read_cons = read;
+				ao_scheme_read_cons_tail = read;
+			}
+
+			if (!(read_state & READ_IN_QUOTE) || !ao_scheme_read_cons->cdr)
+				break;
+
+			v = ao_scheme_cons_poly(ao_scheme_read_cons);
+			--cons;
+			read_state = pop_read_stack(cons);
+		}
+	}
+	return v;
+}
diff --git a/src/scheme/ao_scheme_read.h b/src/scheme/ao_scheme_read.h
new file mode 100644
index 00000000..e9508835
--- /dev/null
+++ b/src/scheme/ao_scheme_read.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#ifndef _AO_SCHEME_READ_H_
+#define _AO_SCHEME_READ_H_
+
+/*
+ * token classes
+ */
+
+# define END			0
+# define NAME			1
+# define OPEN  			2
+# define CLOSE			3
+# define QUOTE			4
+# define QUASIQUOTE		5
+# define UNQUOTE		6
+# define UNQUOTE_SPLICING	7
+# define STRING			8
+# define NUM			9
+# define FLOAT			10
+# define DOT			11
+# define BOOL			12
+
+/*
+ * character classes
+ */
+
+# define PRINTABLE	0x0001	/* \t \n ' ' - ~ */
+# define SPECIAL	0x0002	/* ( [ { ) ] } ' ` , */
+# define DOTC		0x0004	/* . */
+# define WHITE		0x0008	/* ' ' \t \n */
+# define DIGIT		0x0010	/* [0-9] */
+# define SIGN		0x0020	/* +- */
+# define FLOATC		0x0040	/* . e E */
+# define ENDOFFILE	0x0080	/* end of file */
+# define COMMENT	0x0100	/* ; */
+# define IGNORE		0x0200	/* \0 - ' ' */
+# define BACKSLASH	0x0400	/* \ */
+# define STRINGC	0x0800	/* " */
+# define POUND		0x1000	/* # */
+
+# define NOTNAME	(STRINGC|COMMENT|ENDOFFILE|WHITE|SPECIAL)
+# define INTEGER	(DIGIT|SIGN)
+# define NUMBER		(INTEGER|FLOATC)
+
+#endif /* _AO_SCHEME_READ_H_ */
diff --git a/src/scheme/ao_scheme_rep.c b/src/scheme/ao_scheme_rep.c
new file mode 100644
index 00000000..9dbce5f2
--- /dev/null
+++ b/src/scheme/ao_scheme_rep.c
@@ -0,0 +1,36 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+ao_poly
+ao_scheme_read_eval_print(void)
+{
+	ao_poly	in, out = AO_SCHEME_NIL;
+	for(;;) {
+		in = ao_scheme_read();
+		if (in == _ao_scheme_atom_eof)
+			break;
+		out = ao_scheme_eval(in);
+		if (ao_scheme_exception) {
+			if (ao_scheme_exception & AO_SCHEME_EXIT)
+				break;
+			ao_scheme_exception = 0;
+		} else {
+			ao_scheme_poly_write(out);
+			putchar ('\n');
+		}
+	}
+	return out;
+}
diff --git a/src/scheme/ao_scheme_save.c b/src/scheme/ao_scheme_save.c
new file mode 100644
index 00000000..af9345b8
--- /dev/null
+++ b/src/scheme/ao_scheme_save.c
@@ -0,0 +1,77 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+ao_poly
+ao_scheme_do_save(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_save, cons, 0, 0))
+		return AO_SCHEME_NIL;
+
+#ifdef AO_SCHEME_SAVE
+	struct ao_scheme_os_save *os = (struct ao_scheme_os_save *) (void *) &ao_scheme_pool[AO_SCHEME_POOL];
+
+	ao_scheme_collect(AO_SCHEME_COLLECT_FULL);
+	os->atoms = ao_scheme_atom_poly(ao_scheme_atoms);
+	os->globals = ao_scheme_frame_poly(ao_scheme_frame_global);
+	os->const_checksum = ao_scheme_const_checksum;
+	os->const_checksum_inv = (uint16_t) ~ao_scheme_const_checksum;
+
+	if (ao_scheme_os_save())
+		return _ao_scheme_bool_true;
+#endif
+	return _ao_scheme_bool_false;
+}
+
+ao_poly
+ao_scheme_do_restore(struct ao_scheme_cons *cons)
+{
+	if (!ao_scheme_check_argc(_ao_scheme_atom_save, cons, 0, 0))
+		return AO_SCHEME_NIL;
+
+#ifdef AO_SCHEME_SAVE
+	struct ao_scheme_os_save save;
+	struct ao_scheme_os_save *os = (struct ao_scheme_os_save *) (void *) &ao_scheme_pool[AO_SCHEME_POOL];
+
+	if (!ao_scheme_os_restore_save(&save, AO_SCHEME_POOL))
+		return ao_scheme_error(AO_SCHEME_INVALID, "header restore failed");
+
+	if (save.const_checksum != ao_scheme_const_checksum ||
+	    save.const_checksum_inv != (uint16_t) ~ao_scheme_const_checksum)
+	{
+		return ao_scheme_error(AO_SCHEME_INVALID, "image is corrupted or stale");
+	}
+
+	if (ao_scheme_os_restore()) {
+
+		ao_scheme_atoms = ao_scheme_poly_atom(os->atoms);
+		ao_scheme_frame_global = ao_scheme_poly_frame(os->globals);
+
+		/* Clear the eval global variabls */
+		ao_scheme_eval_clear_globals();
+
+		/* Reset the allocator */
+		ao_scheme_top = AO_SCHEME_POOL;
+		ao_scheme_collect(AO_SCHEME_COLLECT_FULL);
+
+		/* Re-create the evaluator stack */
+		if (!ao_scheme_eval_restart())
+			return _ao_scheme_bool_false;
+
+		return _ao_scheme_bool_true;
+	}
+#endif
+	return _ao_scheme_bool_false;
+}
diff --git a/src/scheme/ao_scheme_stack.c b/src/scheme/ao_scheme_stack.c
new file mode 100644
index 00000000..d19dd6d6
--- /dev/null
+++ b/src/scheme/ao_scheme_stack.c
@@ -0,0 +1,280 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+
+const struct ao_scheme_type ao_scheme_stack_type;
+
+static int
+stack_size(void *addr)
+{
+	(void) addr;
+	return sizeof (struct ao_scheme_stack);
+}
+
+static void
+stack_mark(void *addr)
+{
+	struct ao_scheme_stack	*stack = addr;
+	for (;;) {
+		ao_scheme_poly_mark(stack->sexprs, 0);
+		ao_scheme_poly_mark(stack->values, 0);
+		/* no need to mark values_tail */
+		ao_scheme_poly_mark(stack->frame, 0);
+		ao_scheme_poly_mark(stack->list, 0);
+		stack = ao_scheme_poly_stack(stack->prev);
+		if (ao_scheme_mark_memory(&ao_scheme_stack_type, stack))
+			break;
+	}
+}
+
+static void
+stack_move(void *addr)
+{
+	struct ao_scheme_stack	*stack = addr;
+
+	while (stack) {
+		struct ao_scheme_stack	*prev;
+		int			ret;
+		(void) ao_scheme_poly_move(&stack->sexprs, 0);
+		(void) ao_scheme_poly_move(&stack->values, 0);
+		(void) ao_scheme_poly_move(&stack->values_tail, 0);
+		(void) ao_scheme_poly_move(&stack->frame, 0);
+		(void) ao_scheme_poly_move(&stack->list, 0);
+		prev = ao_scheme_poly_stack(stack->prev);
+		if (!prev)
+			break;
+		ret = ao_scheme_move_memory(&ao_scheme_stack_type, (void **) &prev);
+		if (prev != ao_scheme_poly_stack(stack->prev))
+			stack->prev = ao_scheme_stack_poly(prev);
+		if (ret)
+			break;
+		stack = prev;
+	}
+}
+
+const struct ao_scheme_type ao_scheme_stack_type = {
+	.size = stack_size,
+	.mark = stack_mark,
+	.move = stack_move,
+	.name = "stack"
+};
+
+struct ao_scheme_stack		*ao_scheme_stack_free_list;
+
+void
+ao_scheme_stack_reset(struct ao_scheme_stack *stack)
+{
+	stack->state = eval_sexpr;
+	stack->sexprs = AO_SCHEME_NIL;
+	stack->values = AO_SCHEME_NIL;
+	stack->values_tail = AO_SCHEME_NIL;
+}
+
+static struct ao_scheme_stack *
+ao_scheme_stack_new(void)
+{
+	struct ao_scheme_stack *stack;
+
+	if (ao_scheme_stack_free_list) {
+		stack = ao_scheme_stack_free_list;
+		ao_scheme_stack_free_list = ao_scheme_poly_stack(stack->prev);
+	} else {
+		stack = ao_scheme_alloc(sizeof (struct ao_scheme_stack));
+		if (!stack)
+			return 0;
+		stack->type = AO_SCHEME_STACK;
+	}
+	ao_scheme_stack_reset(stack);
+	return stack;
+}
+
+int
+ao_scheme_stack_push(void)
+{
+	struct ao_scheme_stack	*stack;
+
+	stack = ao_scheme_stack_new();
+
+	if (!stack)
+		return 0;
+
+	stack->prev = ao_scheme_stack_poly(ao_scheme_stack);
+	stack->frame = ao_scheme_frame_poly(ao_scheme_frame_current);
+	stack->list = AO_SCHEME_NIL;
+
+	ao_scheme_stack = stack;
+
+	DBGI("stack push\n");
+	DBG_FRAMES();
+	DBG_IN();
+	return 1;
+}
+
+void
+ao_scheme_stack_pop(void)
+{
+	ao_poly			prev;
+	struct ao_scheme_frame	*prev_frame;
+
+	if (!ao_scheme_stack)
+		return;
+	prev = ao_scheme_stack->prev;
+	if (!ao_scheme_stack_marked(ao_scheme_stack)) {
+		ao_scheme_stack->prev = ao_scheme_stack_poly(ao_scheme_stack_free_list);
+		ao_scheme_stack_free_list = ao_scheme_stack;
+	}
+
+	ao_scheme_stack = ao_scheme_poly_stack(prev);
+	prev_frame = ao_scheme_frame_current;
+	if (ao_scheme_stack)
+		ao_scheme_frame_current = ao_scheme_poly_frame(ao_scheme_stack->frame);
+	else
+		ao_scheme_frame_current = NULL;
+	if (ao_scheme_frame_current != prev_frame)
+		ao_scheme_frame_free(prev_frame);
+	DBG_OUT();
+	DBGI("stack pop\n");
+	DBG_FRAMES();
+}
+
+void
+ao_scheme_stack_clear(void)
+{
+	ao_scheme_stack = NULL;
+	ao_scheme_frame_current = NULL;
+	ao_scheme_v = AO_SCHEME_NIL;
+}
+
+void
+ao_scheme_stack_write(ao_poly poly)
+{
+	struct ao_scheme_stack *s = ao_scheme_poly_stack(poly);
+
+	while (s) {
+		if (s->type & AO_SCHEME_STACK_PRINT) {
+			printf("[recurse...]");
+			return;
+		}
+		s->type |= AO_SCHEME_STACK_PRINT;
+		printf("\t[\n");
+		printf("\t\texpr:   "); ao_scheme_poly_write(s->list); printf("\n");
+		printf("\t\tstate:  %s\n", ao_scheme_state_names[s->state]);
+		ao_scheme_error_poly ("values: ", s->values, s->values_tail);
+		ao_scheme_error_poly ("sexprs: ", s->sexprs, AO_SCHEME_NIL);
+		ao_scheme_error_frame(2, "frame:  ", ao_scheme_poly_frame(s->frame));
+		printf("\t]\n");
+		s->type &= ~AO_SCHEME_STACK_PRINT;
+		s = ao_scheme_poly_stack(s->prev);
+	}
+}
+
+/*
+ * Copy a stack, being careful to keep everybody referenced
+ */
+static struct ao_scheme_stack *
+ao_scheme_stack_copy(struct ao_scheme_stack *old)
+{
+	struct ao_scheme_stack *new = NULL;
+	struct ao_scheme_stack *n, *prev = NULL;
+
+	while (old) {
+		ao_scheme_stack_stash(0, old);
+		ao_scheme_stack_stash(1, new);
+		ao_scheme_stack_stash(2, prev);
+		n = ao_scheme_stack_new();
+		prev = ao_scheme_stack_fetch(2);
+		new = ao_scheme_stack_fetch(1);
+		old = ao_scheme_stack_fetch(0);
+		if (!n)
+			return NULL;
+
+		ao_scheme_stack_mark(old);
+		ao_scheme_frame_mark(ao_scheme_poly_frame(old->frame));
+		*n = *old;
+
+		if (prev)
+			prev->prev = ao_scheme_stack_poly(n);
+		else
+			new = n;
+		prev = n;
+
+		old = ao_scheme_poly_stack(old->prev);
+	}
+	return new;
+}
+
+/*
+ * Evaluate a continuation invocation
+ */
+ao_poly
+ao_scheme_stack_eval(void)
+{
+	struct ao_scheme_stack	*new = ao_scheme_stack_copy(ao_scheme_poly_stack(ao_scheme_v));
+	if (!new)
+		return AO_SCHEME_NIL;
+
+	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(ao_scheme_stack->values);
+
+	if (!cons || !cons->cdr)
+		return ao_scheme_error(AO_SCHEME_INVALID, "continuation requires a value");
+
+	new->state = eval_val;
+
+	ao_scheme_stack = new;
+	ao_scheme_frame_current = ao_scheme_poly_frame(ao_scheme_stack->frame);
+
+	return ao_scheme_poly_cons(cons->cdr)->car;
+}
+
+/*
+ * Call with current continuation. This calls a lambda, passing
+ * it a single argument which is the current continuation
+ */
+ao_poly
+ao_scheme_do_call_cc(struct ao_scheme_cons *cons)
+{
+	struct ao_scheme_stack	*new;
+	ao_poly			v;
+
+	/* Make sure the single parameter is a lambda */
+	if (!ao_scheme_check_argc(_ao_scheme_atom_call2fcc, cons, 1, 1))
+		return AO_SCHEME_NIL;
+	if (!ao_scheme_check_argt(_ao_scheme_atom_call2fcc, cons, 0, AO_SCHEME_LAMBDA, 0))
+		return AO_SCHEME_NIL;
+
+	/* go get the lambda */
+	ao_scheme_v = ao_scheme_arg(cons, 0);
+
+	/* Note that the whole call chain now has
+	 * a reference to it which may escape
+	 */
+	new = ao_scheme_stack_copy(ao_scheme_stack);
+	if (!new)
+		return AO_SCHEME_NIL;
+
+	/* re-fetch cons after the allocation */
+	cons = ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->values)->cdr);
+
+	/* Reset the arg list to the current stack,
+	 * and call the lambda
+	 */
+
+	cons->car = ao_scheme_stack_poly(new);
+	cons->cdr = AO_SCHEME_NIL;
+	v = ao_scheme_lambda_eval();
+	ao_scheme_stack->sexprs = v;
+	ao_scheme_stack->state = eval_begin;
+	return AO_SCHEME_NIL;
+}
diff --git a/src/scheme/ao_scheme_string.c b/src/scheme/ao_scheme_string.c
new file mode 100644
index 00000000..e25306cb
--- /dev/null
+++ b/src/scheme/ao_scheme_string.c
@@ -0,0 +1,161 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao_scheme.h"
+
+static void string_mark(void *addr)
+{
+	(void) addr;
+}
+
+static int string_size(void *addr)
+{
+	if (!addr)
+		return 0;
+	return strlen(addr) + 1;
+}
+
+static void string_move(void *addr)
+{
+	(void) addr;
+}
+
+const struct ao_scheme_type ao_scheme_string_type = {
+	.mark = string_mark,
+	.size = string_size,
+	.move = string_move,
+	.name = "string",
+};
+
+char *
+ao_scheme_string_copy(char *a)
+{
+	int	alen = strlen(a);
+
+	ao_scheme_string_stash(0, a);
+	char	*r = ao_scheme_alloc(alen + 1);
+	a = ao_scheme_string_fetch(0);
+	if (!r)
+		return NULL;
+	strcpy(r, a);
+	return r;
+}
+
+char *
+ao_scheme_string_cat(char *a, char *b)
+{
+	int	alen = strlen(a);
+	int	blen = strlen(b);
+
+	ao_scheme_string_stash(0, a);
+	ao_scheme_string_stash(1, b);
+	char	*r = ao_scheme_alloc(alen + blen + 1);
+	a = ao_scheme_string_fetch(0);
+	b = ao_scheme_string_fetch(1);
+	if (!r)
+		return NULL;
+	strcpy(r, a);
+	strcpy(r+alen, b);
+	return r;
+}
+
+ao_poly
+ao_scheme_string_pack(struct ao_scheme_cons *cons)
+{
+	int	len = ao_scheme_cons_length(cons);
+	ao_scheme_cons_stash(0, cons);
+	char	*r = ao_scheme_alloc(len + 1);
+	cons = ao_scheme_cons_fetch(0);
+	char	*s = r;
+
+	while (cons) {
+		if (!ao_scheme_integer_typep(ao_scheme_poly_type(cons->car)))
+			return ao_scheme_error(AO_SCHEME_INVALID, "non-int passed to pack");
+		*s++ = ao_scheme_poly_integer(cons->car);
+		cons = ao_scheme_poly_cons(cons->cdr);
+	}
+	*s++ = 0;
+	return ao_scheme_string_poly(r);
+}
+
+ao_poly
+ao_scheme_string_unpack(char *a)
+{
+	struct ao_scheme_cons	*cons = NULL, *tail = NULL;
+	int			c;
+	int			i;
+
+	for (i = 0; (c = a[i]); i++) {
+		ao_scheme_cons_stash(0, cons);
+		ao_scheme_cons_stash(1, tail);
+		ao_scheme_string_stash(0, a);
+		struct ao_scheme_cons	*n = ao_scheme_cons_cons(ao_scheme_int_poly(c), AO_SCHEME_NIL);
+		a = ao_scheme_string_fetch(0);
+		cons = ao_scheme_cons_fetch(0);
+		tail = ao_scheme_cons_fetch(1);
+
+		if (!n) {
+			cons = NULL;
+			break;
+		}
+		if (tail)
+			tail->cdr = ao_scheme_cons_poly(n);
+		else
+			cons = n;
+		tail = n;
+	}
+	return ao_scheme_cons_poly(cons);
+}
+
+void
+ao_scheme_string_write(ao_poly p)
+{
+	char	*s = ao_scheme_poly_string(p);
+	char	c;
+
+	putchar('"');
+	while ((c = *s++)) {
+		switch (c) {
+		case '\n':
+			printf ("\\n");
+			break;
+		case '\r':
+			printf ("\\r");
+			break;
+		case '\t':
+			printf ("\\t");
+			break;
+		default:
+			if (c < ' ')
+				printf("\\%03o", c);
+			else
+				putchar(c);
+			break;
+		}
+	}
+	putchar('"');
+}
+
+void
+ao_scheme_string_display(ao_poly p)
+{
+	char	*s = ao_scheme_poly_string(p);
+	char	c;
+
+	while ((c = *s++))
+		putchar(c);
+}
diff --git a/src/scheme/make-const/.gitignore b/src/scheme/make-const/.gitignore
new file mode 100644
index 00000000..bcd57242
--- /dev/null
+++ b/src/scheme/make-const/.gitignore
@@ -0,0 +1 @@
+ao_scheme_make_const
diff --git a/src/scheme/make-const/Makefile b/src/scheme/make-const/Makefile
new file mode 100644
index 00000000..caf7acbe
--- /dev/null
+++ b/src/scheme/make-const/Makefile
@@ -0,0 +1,26 @@
+include ../Makefile-inc
+
+vpath %.o .
+vpath %.c ..
+vpath %.h ..
+
+SRCS=$(SCHEME_SRCS) ao_scheme_make_const.c
+HDRS=$(SCHEME_HDRS) ao_scheme_os.h
+
+OBJS=$(SRCS:.c=.o)
+
+CC=cc
+CFLAGS=-DAO_SCHEME_MAKE_CONST -O0 -g -I. -Wall -Wextra
+
+.c.o:
+	$(CC) -c $(CFLAGS) $< -o $@
+
+all: ao_scheme_make_const
+
+ao_scheme_make_const: $(OBJS)
+	$(CC) $(CFLAGS) -o $@ $^ -lm
+
+clean:
+	rm -f $(OBJS) ao_scheme_make_const
+
+$(OBJS): $(SCHEME_HDRS)
diff --git a/src/scheme/make-const/ao_scheme_os.h b/src/scheme/make-const/ao_scheme_os.h
new file mode 100644
index 00000000..f06bbbb1
--- /dev/null
+++ b/src/scheme/make-const/ao_scheme_os.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#ifndef _AO_SCHEME_OS_H_
+#define _AO_SCHEME_OS_H_
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+extern int ao_scheme_getc(void);
+
+static inline void
+ao_scheme_os_flush(void) {
+	fflush(stdout);
+}
+
+static inline void
+ao_scheme_abort(void)
+{
+	abort();
+}
+
+static inline void
+ao_scheme_os_led(int led)
+{
+	printf("leds set to 0x%x\n", led);
+}
+
+#define AO_SCHEME_JIFFIES_PER_SECOND	100
+
+static inline void
+ao_scheme_os_delay(int jiffies)
+{
+	struct timespec ts = {
+		.tv_sec = jiffies / AO_SCHEME_JIFFIES_PER_SECOND,
+		.tv_nsec = (jiffies % AO_SCHEME_JIFFIES_PER_SECOND) * (1000000000L / AO_SCHEME_JIFFIES_PER_SECOND)
+	};
+	nanosleep(&ts, NULL);
+}
+
+static inline int
+ao_scheme_os_jiffy(void)
+{
+	struct timespec tp;
+	clock_gettime(CLOCK_MONOTONIC, &tp);
+	return tp.tv_sec * AO_SCHEME_JIFFIES_PER_SECOND + (tp.tv_nsec / (1000000000L / AO_SCHEME_JIFFIES_PER_SECOND));
+}
+#endif
diff --git a/src/scheme/test/.gitignore b/src/scheme/test/.gitignore
new file mode 100644
index 00000000..3cdae594
--- /dev/null
+++ b/src/scheme/test/.gitignore
@@ -0,0 +1 @@
+ao_scheme_test
diff --git a/src/scheme/test/ao_scheme_os.h b/src/scheme/test/ao_scheme_os.h
new file mode 100644
index 00000000..09a945bc
--- /dev/null
+++ b/src/scheme/test/ao_scheme_os.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#ifndef _AO_SCHEME_OS_H_
+#define _AO_SCHEME_OS_H_
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define AO_SCHEME_POOL_TOTAL	16384
+#define AO_SCHEME_SAVE		1
+#define DBG_MEM_STATS		1
+
+extern int ao_scheme_getc(void);
+
+static inline void
+ao_scheme_os_flush() {
+	fflush(stdout);
+}
+
+static inline void
+ao_scheme_abort(void)
+{
+	abort();
+}
+
+static inline void
+ao_scheme_os_led(int led)
+{
+	printf("leds set to 0x%x\n", led);
+}
+
+#define AO_SCHEME_JIFFIES_PER_SECOND	100
+
+static inline void
+ao_scheme_os_delay(int jiffies)
+{
+	struct timespec ts = {
+		.tv_sec = jiffies / AO_SCHEME_JIFFIES_PER_SECOND,
+		.tv_nsec = (jiffies % AO_SCHEME_JIFFIES_PER_SECOND) * (1000000000L / AO_SCHEME_JIFFIES_PER_SECOND)
+	};
+	nanosleep(&ts, NULL);
+}
+
+static inline int
+ao_scheme_os_jiffy(void)
+{
+	struct timespec tp;
+	clock_gettime(CLOCK_MONOTONIC, &tp);
+	return tp.tv_sec * AO_SCHEME_JIFFIES_PER_SECOND + (tp.tv_nsec / (1000000000L / AO_SCHEME_JIFFIES_PER_SECOND));
+}
+
+#endif
diff --git a/src/scheme/test/ao_scheme_test.c b/src/scheme/test/ao_scheme_test.c
new file mode 100644
index 00000000..15c71203
--- /dev/null
+++ b/src/scheme/test/ao_scheme_test.c
@@ -0,0 +1,139 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include "ao_scheme.h"
+#include <stdio.h>
+
+static FILE *ao_scheme_file;
+static int newline = 1;
+
+static char save_file[] = "scheme.image";
+
+int
+ao_scheme_os_save(void)
+{
+	FILE	*save = fopen(save_file, "w");
+
+	if (!save) {
+		perror(save_file);
+		return 0;
+	}
+	fwrite(ao_scheme_pool, 1, AO_SCHEME_POOL_TOTAL, save);
+	fclose(save);
+	return 1;
+}
+
+int
+ao_scheme_os_restore_save(struct ao_scheme_os_save *save, int offset)
+{
+	FILE	*restore = fopen(save_file, "r");
+	size_t	ret;
+
+	if (!restore) {
+		perror(save_file);
+		return 0;
+	}
+	fseek(restore, offset, SEEK_SET);
+	ret = fread(save, sizeof (struct ao_scheme_os_save), 1, restore);
+	fclose(restore);
+	if (ret != 1)
+		return 0;
+	return 1;
+}
+
+int
+ao_scheme_os_restore(void)
+{
+	FILE	*restore = fopen(save_file, "r");
+	size_t	ret;
+
+	if (!restore) {
+		perror(save_file);
+		return 0;
+	}
+	ret = fread(ao_scheme_pool, 1, AO_SCHEME_POOL_TOTAL, restore);
+	fclose(restore);
+	if (ret != AO_SCHEME_POOL_TOTAL)
+		return 0;
+	return 1;
+}
+
+int
+ao_scheme_getc(void)
+{
+	int c;
+
+	if (ao_scheme_file)
+		return getc(ao_scheme_file);
+
+	if (newline) {
+		if (ao_scheme_read_stack)
+			printf("+ ");
+		else
+			printf("> ");
+		newline = 0;
+	}
+	c = getchar();
+	if (c == '\n')
+		newline = 1;
+	return c;
+}
+
+int
+main (int argc, char **argv)
+{
+	(void) argc;
+
+	while (*++argv) {
+		ao_scheme_file = fopen(*argv, "r");
+		if (!ao_scheme_file) {
+			perror(*argv);
+			exit(1);
+		}
+		ao_scheme_read_eval_print();
+		fclose(ao_scheme_file);
+		ao_scheme_file = NULL;
+	}
+	ao_scheme_read_eval_print();
+
+	printf ("collects: full: %d incremental %d\n",
+		ao_scheme_collects[AO_SCHEME_COLLECT_FULL],
+		ao_scheme_collects[AO_SCHEME_COLLECT_INCREMENTAL]);
+
+	printf ("freed: full %d incremental %d\n",
+		ao_scheme_freed[AO_SCHEME_COLLECT_FULL],
+		ao_scheme_freed[AO_SCHEME_COLLECT_INCREMENTAL]);
+
+	printf("loops: full %d incremental %d\n",
+		ao_scheme_loops[AO_SCHEME_COLLECT_FULL],
+		ao_scheme_loops[AO_SCHEME_COLLECT_INCREMENTAL]);
+
+	printf("loops per collect: full %f incremental %f\n",
+	       (double) ao_scheme_loops[AO_SCHEME_COLLECT_FULL] /
+	       (double) ao_scheme_collects[AO_SCHEME_COLLECT_FULL],
+	       (double) ao_scheme_loops[AO_SCHEME_COLLECT_INCREMENTAL] /
+	       (double) ao_scheme_collects[AO_SCHEME_COLLECT_INCREMENTAL]);
+
+	printf("freed per collect: full %f incremental %f\n",
+	       (double) ao_scheme_freed[AO_SCHEME_COLLECT_FULL] /
+	       (double) ao_scheme_collects[AO_SCHEME_COLLECT_FULL],
+	       (double) ao_scheme_freed[AO_SCHEME_COLLECT_INCREMENTAL] /
+	       (double) ao_scheme_collects[AO_SCHEME_COLLECT_INCREMENTAL]);
+
+	printf("freed per loop: full %f incremental %f\n",
+	       (double) ao_scheme_freed[AO_SCHEME_COLLECT_FULL] /
+	       (double) ao_scheme_loops[AO_SCHEME_COLLECT_FULL],
+	       (double) ao_scheme_freed[AO_SCHEME_COLLECT_INCREMENTAL] /
+	       (double) ao_scheme_loops[AO_SCHEME_COLLECT_INCREMENTAL]);
+}
diff --git a/src/scheme/test/hanoi.scheme b/src/scheme/test/hanoi.scheme
new file mode 100644
index 00000000..c4ae7378
--- /dev/null
+++ b/src/scheme/test/hanoi.scheme
@@ -0,0 +1,174 @@
+;
+; Towers of Hanoi
+;
+; Copyright © 2016 Keith Packard <keithp@keithp.com>
+;
+; This program is free software; you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, either version 2 of the License, or
+; (at your option) any later version.
+;
+; This program is distributed in the hope that it will be useful, but
+; WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+; General Public License for more details.
+;
+
+					; ANSI control sequences
+
+(define (move-to col row)
+  (for-each display (list "\033[" row ";" col "H"))
+  )
+
+(define (clear)
+  (display "\033[2J")
+  )
+
+(define (display-string x y str)
+  (move-to x y)
+  (display str)
+  )
+
+(define (make-piece num max)
+					; A piece for position 'num'
+					; is num + 1 + num stars
+					; centered in a field of max *
+					; 2 + 1 characters with spaces
+					; on either side. This way,
+					; every piece is the same
+					; number of characters
+
+  (define (chars n c)
+    (if (zero? n) ""
+      (+ c (chars (- n 1) c))
+      )
+    )
+  (+ (chars (- max num 1) " ")
+     (chars (+ (* num 2) 1) "*")
+     (chars (- max num 1) " ")
+     )
+  )
+
+(define (make-pieces max)
+					; Make a list of numbers from 0 to max-1
+  (define (nums cur max)
+    (if (= cur max) ()
+      (cons cur (nums (+ cur 1) max))
+      )
+    )
+					; Create a list of pieces
+
+  (map (lambda (x) (make-piece x max)) (nums 0 max))
+  )
+
+					; Here's all of the towers of pieces
+					; This is generated when the program is run
+
+(define towers ())
+
+					; position of the bottom of
+					; the stacks set at runtime
+(define bottom-y 0)
+(define left-x 0)
+
+(define move-delay 25)
+
+					; Display one tower, clearing any
+					; space above it
+
+(define (display-tower x y clear tower)
+  (cond ((= 0 clear)
+	 (cond ((not (null? tower))
+		(display-string x y (car tower))
+		(display-tower x (+ y 1) 0 (cdr tower))
+		)
+	       )
+	 )
+	(else 
+	 (display-string x y "                    ")
+	 (display-tower x (+ y 1) (- clear 1) tower)
+	 )
+	)
+  )
+
+					; Position of the top of the tower on the screen
+					; Shorter towers start further down the screen
+
+(define (tower-pos tower)
+  (- bottom-y (length tower))
+  )
+
+					; Display all of the towers, spaced 20 columns apart
+
+(define (display-towers x towers)
+  (cond ((not (null? towers))
+	 (display-tower x 0 (tower-pos (car towers)) (car towers))
+	 (display-towers (+ x 20) (cdr towers)))
+	)
+  )
+
+					; Display all of the towers, then move the cursor
+					; out of the way and flush the output
+
+(define (display-hanoi)
+  (display-towers left-x towers)
+  (move-to 1 23)
+  (flush-output)
+  (delay move-delay)
+  )
+
+					; Reset towers to the starting state, with
+					; all of the pieces in the first tower and the
+					; other two empty
+
+(define (reset-towers len)
+  (set! towers (list (make-pieces len) () ()))
+  (set! bottom-y (+ len 3))
+  )
+
+					; Move a piece from the top of one tower
+					; to the top of another
+
+(define (move-piece from to)
+
+					; references to the cons holding the two towers
+
+  (define from-tower (list-tail towers from))
+  (define to-tower (list-tail towers to))
+
+					; stick the car of from-tower onto to-tower
+
+  (set-car! to-tower (cons (caar from-tower) (car to-tower)))
+
+					; remove the car of from-tower
+
+  (set-car! from-tower (cdar from-tower))
+  )
+
+					; The implementation of the game
+
+(define (_hanoi n from to use)
+  (cond ((= 1 n)
+	 (move-piece from to)
+	 (display-hanoi)
+	 )
+	(else
+	 (_hanoi (- n 1) from use to)
+	 (_hanoi 1 from to use)
+	 (_hanoi (- n 1) use to from)
+	 )
+	)
+  )
+
+					; A pretty interface which
+					; resets the state of the game,
+					; clears the screen and runs
+					; the program
+
+(define (hanoi len)
+  (reset-towers len)
+  (clear)
+  (display-hanoi)
+  (_hanoi len 0 1 2)
+  #t
+  )