1 files changed, 572 insertions, 0 deletions

diff --git a/src/scheme/ao_scheme_eval.c b/src/scheme/ao_scheme_eval.c
new file mode 100644
index 00000000..907ecf0b
--- /dev/null
+++ b/src/scheme/ao_scheme_eval.c
@@ -0,0 +1,572 @@
+/*
+ * 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 */
+	default:
+		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;
+}