2 * Copyright © 2016 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
15 #include "ao_scheme.h"
18 struct ao_scheme_stack *ao_scheme_stack;
20 uint8_t ao_scheme_skip_cons_free;
23 ao_scheme_set_cond(struct ao_scheme_cons *c)
25 ao_scheme_stack->state = eval_cond;
26 ao_scheme_stack->sexprs = ao_scheme_cons_poly(c);
31 func_type(ao_poly func)
33 if (func == AO_SCHEME_NIL)
34 return ao_scheme_error(AO_SCHEME_INVALID, "func is nil");
35 switch (ao_scheme_poly_type(func)) {
36 case AO_SCHEME_BUILTIN:
37 return ao_scheme_poly_builtin(func)->args & AO_SCHEME_FUNC_MASK;
38 case AO_SCHEME_LAMBDA:
39 return ao_scheme_poly_lambda(func)->args;
41 return AO_SCHEME_FUNC_LAMBDA;
43 ao_scheme_error(AO_SCHEME_INVALID, "not a func");
49 * Flattened eval to avoid stack issues
53 * Evaluate an s-expression
55 * For a list, evaluate all of the elements and
56 * then execute the resulting function call.
58 * Each element of the list is evaluated in
59 * a clean stack context.
61 * The current stack state is set to 'formal' so that
62 * when the evaluation is complete, the value
63 * will get appended to the values list.
65 * For other types, compute the value directly.
69 ao_scheme_eval_sexpr(void)
71 DBGI("sexpr: %v\n", ao_scheme_v);
72 switch (ao_scheme_poly_type(ao_scheme_v)) {
74 if (ao_scheme_v == AO_SCHEME_NIL) {
75 if (!ao_scheme_stack->values) {
77 * empty list evaluates to empty list
79 ao_scheme_v = AO_SCHEME_NIL;
80 ao_scheme_stack->state = eval_val;
83 * done with arguments, go execute it
85 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
86 ao_scheme_stack->state = eval_exec;
89 if (!ao_scheme_stack->values)
90 ao_scheme_stack->list = ao_scheme_v;
92 * Evaluate another argument and then switch
93 * to 'formal' to add the value to the values
96 ao_scheme_stack->sexprs = ao_scheme_v;
97 ao_scheme_stack->state = eval_formal;
98 if (!ao_scheme_stack_push())
101 * push will reset the state to 'sexpr', which
102 * will evaluate the expression
104 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
108 DBGI("..frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
109 ao_scheme_v = ao_scheme_atom_get(ao_scheme_v);
112 ao_scheme_stack->state = eval_val;
115 DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG("\n");
120 * A value has been computed.
122 * If the value was computed from a macro,
123 * then we want to reset the current context
124 * to evaluate the macro result again.
126 * If not a macro, then pop the stack.
127 * If the stack is empty, we're done.
128 * Otherwise, the stack will contain
133 ao_scheme_eval_val(void)
135 DBGI("val: "); DBG_POLY(ao_scheme_v); DBG("\n");
137 * Value computed, pop the stack
138 * to figure out what to do with the value
140 ao_scheme_stack_pop();
141 DBGI("..state %d\n", ao_scheme_stack ? ao_scheme_stack->state : -1);
146 * A formal has been computed.
148 * If this is the first formal, then check to see if we've got a
149 * lamda, macro or nlambda.
151 * For lambda, go compute another formal. This will terminate
152 * when the sexpr state sees nil.
154 * For macro/nlambda, we're done, so move the sexprs into the values
157 * Macros have an additional step of saving a stack frame holding the
158 * macro value execution context, which then gets the result of the
163 ao_scheme_eval_formal(void)
166 struct ao_scheme_stack *prev;
168 DBGI("formal: "); DBG_POLY(ao_scheme_v); DBG("\n");
170 /* Check what kind of function we've got */
171 if (!ao_scheme_stack->values) {
172 switch (func_type(ao_scheme_v)) {
173 case AO_SCHEME_FUNC_LAMBDA:
176 case AO_SCHEME_FUNC_MACRO:
177 /* Evaluate the result once more */
178 ao_scheme_stack->state = eval_macro;
179 if (!ao_scheme_stack_push())
182 /* After the function returns, take that
183 * value and re-evaluate it
185 prev = ao_scheme_poly_stack(ao_scheme_stack->prev);
186 ao_scheme_stack->sexprs = prev->sexprs;
188 DBGI(".. start macro\n");
189 DBGI("\t.. sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
190 DBGI("\t.. values "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
193 /* fall through ... */
194 case AO_SCHEME_FUNC_NLAMBDA:
195 DBGI(".. nlambda or macro\n");
197 /* use the raw sexprs as values */
198 ao_scheme_stack->values = ao_scheme_stack->sexprs;
199 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
200 ao_scheme_stack->state = eval_exec;
202 /* ready to execute now */
209 /* Append formal to list of values */
210 formal = ao_scheme__cons(ao_scheme_v, AO_SCHEME_NIL);
214 if (ao_scheme_stack->values_tail)
215 ao_scheme_poly_cons(ao_scheme_stack->values_tail)->cdr = formal;
217 ao_scheme_stack->values = formal;
218 ao_scheme_stack->values_tail = formal;
220 DBGI(".. values "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
223 * Step to the next argument, if this is last, then
224 * 'sexpr' will end up switching to 'exec'
226 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
228 ao_scheme_stack->state = eval_sexpr;
230 DBGI(".. "); DBG_POLY(ao_scheme_v); DBG("\n");
235 * Start executing a function call
237 * Most builtins are easy, just call the function.
238 * 'cond' is magic; it sticks the list of clauses
239 * in 'sexprs' and switches to 'cond' state. That
240 * bit of magic is done in ao_scheme_set_cond.
242 * Lambdas build a new frame to hold the locals and
243 * then re-use the current stack context to evaluate
244 * the s-expression from the lambda.
248 ao_scheme_eval_exec(void)
251 struct ao_scheme_builtin *builtin;
253 DBGI("exec: "); DBG_POLY(ao_scheme_v); DBG(" values "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
254 ao_scheme_stack->sexprs = AO_SCHEME_NIL;
255 switch (ao_scheme_poly_type(ao_scheme_v)) {
256 case AO_SCHEME_BUILTIN:
257 ao_scheme_stack->state = eval_val;
258 builtin = ao_scheme_poly_builtin(ao_scheme_v);
259 v = ao_scheme_func(builtin) (
260 ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->values)->cdr));
261 DBG_DO(if (!ao_scheme_exception && ao_scheme_poly_builtin(ao_scheme_v)->func == builtin_set) {
262 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
263 ao_poly atom = ao_scheme_arg(cons, 1);
264 ao_poly val = ao_scheme_arg(cons, 2);
265 DBGI("set "); DBG_POLY(atom); DBG(" = "); DBG_POLY(val); DBG("\n");
267 builtin = ao_scheme_poly_builtin(ao_scheme_v);
268 if (builtin && (builtin->args & AO_SCHEME_FUNC_FREE_ARGS) && !ao_scheme_stack_marked(ao_scheme_stack) && !ao_scheme_skip_cons_free) {
269 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
270 ao_scheme_stack->values = AO_SCHEME_NIL;
271 ao_scheme_cons_free(cons);
275 ao_scheme_stack->values = AO_SCHEME_NIL;
276 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
277 DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG ("\n");
278 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
280 case AO_SCHEME_LAMBDA:
281 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
282 ao_scheme_stack->state = eval_begin;
283 v = ao_scheme_lambda_eval();
284 ao_scheme_stack->sexprs = v;
285 ao_scheme_stack->values = AO_SCHEME_NIL;
286 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
287 DBGI(".. sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
288 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
290 case AO_SCHEME_STACK:
291 DBGI(".. stack "); DBG_POLY(ao_scheme_v); DBG("\n");
292 ao_scheme_v = ao_scheme_stack_eval();
293 DBGI(".. value "); DBG_POLY(ao_scheme_v); DBG("\n");
294 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
297 ao_scheme_skip_cons_free = 0;
302 * Finish setting up the apply evaluation
304 * The value is the list to execute
307 ao_scheme_eval_apply(void)
309 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_v);
310 struct ao_scheme_cons *cdr, *prev;
312 /* Glue the arguments into the right shape. That's all but the last
313 * concatenated onto the last
318 cdr = ao_scheme_poly_cons(prev->cdr);
319 if (cdr->cdr == AO_SCHEME_NIL)
322 DBGI("before mangling: "); DBG_POLY(ao_scheme_v); DBG("\n");
323 prev->cdr = cdr->car;
324 ao_scheme_stack->values = ao_scheme_v;
325 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
326 DBGI("apply: "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
327 ao_scheme_stack->state = eval_exec;
328 ao_scheme_skip_cons_free = 1;
333 * Start evaluating the next cond clause
335 * If the list of clauses is empty, then
336 * the result of the cond is nil.
338 * Otherwise, set the current stack state to 'cond_test' and create a
339 * new stack context to evaluate the test s-expression. Once that's
340 * complete, we'll land in 'cond_test' to finish the clause.
343 ao_scheme_eval_cond(void)
345 DBGI("cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
346 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
347 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
348 if (!ao_scheme_stack->sexprs) {
349 ao_scheme_v = _ao_scheme_bool_false;
350 ao_scheme_stack->state = eval_val;
352 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
353 if (!ao_scheme_v || ao_scheme_poly_type(ao_scheme_v) != AO_SCHEME_CONS) {
354 ao_scheme_error(AO_SCHEME_INVALID, "invalid cond clause");
357 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
358 if (ao_scheme_v == _ao_scheme_atom_else)
359 ao_scheme_v = _ao_scheme_bool_true;
360 ao_scheme_stack->state = eval_cond_test;
361 if (!ao_scheme_stack_push())
368 * Finish a cond clause.
370 * Check the value from the test expression, if
371 * non-nil, then set up to evaluate the value expression.
373 * Otherwise, step to the next clause and go back to the 'cond'
377 ao_scheme_eval_cond_test(void)
379 DBGI("cond_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
380 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
381 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
382 if (ao_scheme_v != _ao_scheme_bool_false) {
383 struct ao_scheme_cons *car = ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car);
384 ao_poly c = car->cdr;
387 ao_scheme_stack->state = eval_begin;
388 ao_scheme_stack->sexprs = c;
390 ao_scheme_stack->state = eval_val;
392 ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
393 DBGI("next cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
394 ao_scheme_stack->state = eval_cond;
400 * Evaluate a list of sexprs, returning the value from the last one.
402 * ao_scheme_begin records the list in stack->sexprs, so we just need to
403 * walk that list. Set ao_scheme_v to the car of the list and jump to
404 * eval_sexpr. When that's done, it will land in eval_val. For all but
405 * the last, leave a stack frame with eval_begin set so that we come
406 * back here. For the last, don't add a stack frame so that we can
410 ao_scheme_eval_begin(void)
412 DBGI("begin: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
413 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
414 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
416 if (!ao_scheme_stack->sexprs) {
417 ao_scheme_v = AO_SCHEME_NIL;
418 ao_scheme_stack->state = eval_val;
420 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
421 ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
423 /* If there are more sexprs to do, then come back here, otherwise
424 * return the value of the last one by just landing in eval_sexpr
426 if (ao_scheme_stack->sexprs) {
427 ao_scheme_stack->state = eval_begin;
428 if (!ao_scheme_stack_push())
431 ao_scheme_stack->state = eval_sexpr;
437 * Conditionally execute a list of sexprs while the first is true
440 ao_scheme_eval_while(void)
442 DBGI("while: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
443 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
444 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
446 ao_scheme_stack->values = ao_scheme_v;
447 if (!ao_scheme_stack->sexprs) {
448 ao_scheme_v = AO_SCHEME_NIL;
449 ao_scheme_stack->state = eval_val;
451 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
452 ao_scheme_stack->state = eval_while_test;
453 if (!ao_scheme_stack_push())
460 * Check the while condition, terminate the loop if nil. Otherwise keep going
463 ao_scheme_eval_while_test(void)
465 DBGI("while_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
466 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
467 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
469 if (ao_scheme_v != _ao_scheme_bool_false) {
470 ao_scheme_stack->values = ao_scheme_v;
471 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
472 ao_scheme_stack->state = eval_while;
473 if (!ao_scheme_stack_push())
475 ao_scheme_stack->state = eval_begin;
476 ao_scheme_stack->sexprs = ao_scheme_v;
480 ao_scheme_stack->state = eval_val;
481 ao_scheme_v = ao_scheme_stack->values;
487 * Replace the original sexpr with the macro expansion, then
491 ao_scheme_eval_macro(void)
493 DBGI("macro: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
495 if (ao_scheme_v == AO_SCHEME_NIL)
497 if (ao_scheme_poly_type(ao_scheme_v) == AO_SCHEME_CONS) {
498 *ao_scheme_poly_cons(ao_scheme_stack->sexprs) = *ao_scheme_poly_cons(ao_scheme_v);
499 ao_scheme_v = ao_scheme_stack->sexprs;
500 DBGI("sexprs rewritten to: "); DBG_POLY(ao_scheme_v); DBG("\n");
502 ao_scheme_stack->sexprs = AO_SCHEME_NIL;
503 ao_scheme_stack->state = eval_sexpr;
507 static int (*const evals[])(void) = {
508 [eval_sexpr] = ao_scheme_eval_sexpr,
509 [eval_val] = ao_scheme_eval_val,
510 [eval_formal] = ao_scheme_eval_formal,
511 [eval_exec] = ao_scheme_eval_exec,
512 [eval_apply] = ao_scheme_eval_apply,
513 [eval_cond] = ao_scheme_eval_cond,
514 [eval_cond_test] = ao_scheme_eval_cond_test,
515 [eval_begin] = ao_scheme_eval_begin,
516 [eval_while] = ao_scheme_eval_while,
517 [eval_while_test] = ao_scheme_eval_while_test,
518 [eval_macro] = ao_scheme_eval_macro,
521 const char * const ao_scheme_state_names[] = {
522 [eval_sexpr] = "sexpr",
524 [eval_formal] = "formal",
525 [eval_exec] = "exec",
526 [eval_apply] = "apply",
527 [eval_cond] = "cond",
528 [eval_cond_test] = "cond_test",
529 [eval_begin] = "begin",
530 [eval_while] = "while",
531 [eval_while_test] = "while_test",
532 [eval_macro] = "macro",
536 * Called at restore time to reset all execution state
540 ao_scheme_eval_clear_globals(void)
542 ao_scheme_stack = NULL;
543 ao_scheme_frame_current = NULL;
544 ao_scheme_v = AO_SCHEME_NIL;
548 ao_scheme_eval_restart(void)
550 return ao_scheme_stack_push();
554 ao_scheme_eval(ao_poly _v)
558 ao_scheme_frame_init();
560 if (!ao_scheme_stack_push())
561 return AO_SCHEME_NIL;
563 while (ao_scheme_stack) {
564 if (!(*evals[ao_scheme_stack->state])() || ao_scheme_exception) {
565 ao_scheme_stack_clear();
566 return AO_SCHEME_NIL;
569 DBG_DO(if (ao_scheme_frame_current) {DBGI("frame left as "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");});
570 ao_scheme_frame_current = NULL;