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/*
* 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_lisp.h"
/*
* Non-recursive eval
*
* Plan: walk actuals, construct formals
*
* stack > save > actuals > actual_1
* v v
* formals . > actual_2
*/
static struct ao_lisp_cons *stack;
static struct ao_lisp_cons *actuals;
static struct ao_lisp_cons *formals;
static struct ao_lisp_cons *formals_tail;
static uint8_t been_here;
#if 0
#define DBG(...) printf(__VA_ARGS__)
#define DBG_CONS(a) ao_lisp_cons_print(a)
#define DBG_POLY(a) ao_lisp_poly_print(a)
#else
#define DBG(...)
#define DBG_CONS(a)
#define DBG_POLY(a)
#endif
ao_poly
ao_lisp_eval(ao_poly v)
{
struct ao_lisp_cons *formal;
int cons = 0;
if (!been_here) {
been_here = 1;
ao_lisp_root_add(&ao_lisp_cons_type, &stack);
ao_lisp_root_add(&ao_lisp_cons_type, &actuals);
ao_lisp_root_add(&ao_lisp_cons_type, &formals);
ao_lisp_root_add(&ao_lisp_cons_type, &formals_tail);
}
stack = 0;
actuals = 0;
formals = 0;
formals_tail = 0;
for (;;) {
restart:
/* Build stack frames for each list */
while (ao_lisp_poly_type(v) == AO_LISP_CONS) {
if (v == AO_LISP_NIL)
break;
/* Push existing frame on the stack */
if (cons++) {
struct ao_lisp_cons *frame;
frame = ao_lisp_cons_cons(ao_lisp_cons_poly(actuals), formals);
stack = ao_lisp_cons_cons(ao_lisp_cons_poly(frame), stack);
}
actuals = ao_lisp_poly_cons(v);
formals = NULL;
formals_tail = NULL;
v = actuals->car;
DBG("start: stack"); DBG_CONS(stack); DBG("\n");
DBG("start: actuals"); DBG_CONS(actuals); DBG("\n");
DBG("start: formals"); DBG_CONS(formals); DBG("\n");
}
/* Evaluate primitive types */
DBG ("actual: "); DBG_POLY(v); DBG("\n");
switch (ao_lisp_poly_type(v)) {
case AO_LISP_INT:
case AO_LISP_STRING:
break;
case AO_LISP_ATOM:
v = ao_lisp_poly_atom(v)->val;
break;
}
if (!cons)
break;
for (;;) {
DBG("add formal: "); DBG_POLY(v); DBG("\n");
if (formals == NULL) {
if (ao_lisp_poly_type(v) == AO_LISP_BUILTIN) {
struct ao_lisp_builtin *b = ao_lisp_poly_builtin(v);
switch (b->args) {
case AO_LISP_NLAMBDA:
v = ao_lisp_func(b)(ao_lisp_poly_cons(actuals->cdr));
goto done_eval;
case AO_LISP_MACRO:
v = ao_lisp_func(b)(ao_lisp_poly_cons(actuals->cdr));
if (ao_lisp_poly_type(v) != AO_LISP_CONS) {
ao_lisp_exception |= AO_LISP_INVALID;
return AO_LISP_NIL;
}
/* Reset frame to the new list */
actuals = ao_lisp_poly_cons(v);
v = actuals->car;
goto restart;
}
}
}
formal = ao_lisp_cons_cons(v, NULL);
if (formals_tail)
formals_tail->cdr = ao_lisp_cons_poly(formal);
else
formals = formal;
formals_tail = formal;
actuals = ao_lisp_poly_cons(actuals->cdr);
DBG("formals: ");
DBG_CONS(formals);
DBG("\n");
DBG("actuals: ");
DBG_CONS(actuals);
DBG("\n");
/* Process all of the arguments */
if (actuals) {
v = actuals->car;
break;
}
v = formals->car;
/* Evaluate the resulting list */
if (ao_lisp_poly_type(v) == AO_LISP_BUILTIN) {
struct ao_lisp_builtin *b = ao_lisp_poly_builtin(v);
v = ao_lisp_func(b) (ao_lisp_poly_cons(formals->cdr));
DBG ("eval: ");
DBG_CONS(formals);
DBG(" -> ");
DBG_POLY(v);
DBG ("\n");
} else {
ao_lisp_exception |= AO_LISP_INVALID;
return AO_LISP_NIL;
}
done_eval:
if (--cons) {
struct ao_lisp_cons *frame;
/* Pop the previous frame off the stack */
frame = ao_lisp_poly_cons(stack->car);
actuals = ao_lisp_poly_cons(frame->car);
formals = ao_lisp_poly_cons(frame->cdr);
/* Recompute the tail of the formals list */
for (formal = formals; formal->cdr != AO_LISP_NIL; formal = ao_lisp_poly_cons(formal->cdr));
formals_tail = formal;
stack = ao_lisp_poly_cons(stack->cdr);
DBG("stack pop: stack"); DBG_CONS(stack); DBG("\n");
DBG("stack pop: actuals"); DBG_CONS(actuals); DBG("\n");
DBG("stack pop: formals"); DBG_CONS(formals); DBG("\n");
} else {
DBG("done func\n");
break;
}
}
if (!cons)
break;
}
return v;
}
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