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;
22 ao_scheme_set_cond(struct ao_scheme_cons *c)
24 ao_scheme_stack->state = eval_cond;
25 ao_scheme_stack->sexprs = ao_scheme_cons_poly(c);
30 func_type(ao_poly func)
32 if (func == AO_SCHEME_NIL)
33 return ao_scheme_error(AO_SCHEME_INVALID, "func is nil");
34 switch (ao_scheme_poly_type(func)) {
35 case AO_SCHEME_BUILTIN:
36 return ao_scheme_poly_builtin(func)->args & AO_SCHEME_FUNC_MASK;
37 case AO_SCHEME_LAMBDA:
38 return ao_scheme_poly_lambda(func)->args;
40 return AO_SCHEME_FUNC_LAMBDA;
42 ao_scheme_error(AO_SCHEME_INVALID, "not a func");
48 * Flattened eval to avoid stack issues
52 * Evaluate an s-expression
54 * For a list, evaluate all of the elements and
55 * then execute the resulting function call.
57 * Each element of the list is evaluated in
58 * a clean stack context.
60 * The current stack state is set to 'formal' so that
61 * when the evaluation is complete, the value
62 * will get appended to the values list.
64 * For other types, compute the value directly.
68 ao_scheme_eval_sexpr(void)
70 DBGI("sexpr: %v\n", ao_scheme_v);
71 switch (ao_scheme_poly_type(ao_scheme_v)) {
73 if (ao_scheme_v == AO_SCHEME_NIL) {
74 if (!ao_scheme_stack->values) {
76 * empty list evaluates to empty list
78 ao_scheme_v = AO_SCHEME_NIL;
79 ao_scheme_stack->state = eval_val;
82 * done with arguments, go execute it
84 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
85 ao_scheme_stack->state = eval_exec;
88 if (!ao_scheme_stack->values)
89 ao_scheme_stack->list = ao_scheme_v;
91 * Evaluate another argument and then switch
92 * to 'formal' to add the value to the values
95 ao_scheme_stack->sexprs = ao_scheme_v;
96 ao_scheme_stack->state = eval_formal;
97 if (!ao_scheme_stack_push())
100 * push will reset the state to 'sexpr', which
101 * will evaluate the expression
103 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
107 DBGI("..frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
108 ao_scheme_v = ao_scheme_atom_get(ao_scheme_v);
111 ao_scheme_stack->state = eval_val;
114 DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG("\n");
119 * A value has been computed.
121 * If the value was computed from a macro,
122 * then we want to reset the current context
123 * to evaluate the macro result again.
125 * If not a macro, then pop the stack.
126 * If the stack is empty, we're done.
127 * Otherwise, the stack will contain
132 ao_scheme_eval_val(void)
134 DBGI("val: "); DBG_POLY(ao_scheme_v); DBG("\n");
136 * Value computed, pop the stack
137 * to figure out what to do with the value
139 ao_scheme_stack_pop();
140 DBGI("..state %d\n", ao_scheme_stack ? ao_scheme_stack->state : -1);
145 * A formal has been computed.
147 * If this is the first formal, then check to see if we've got a
148 * lamda, macro or nlambda.
150 * For lambda, go compute another formal. This will terminate
151 * when the sexpr state sees nil.
153 * For macro/nlambda, we're done, so move the sexprs into the values
156 * Macros have an additional step of saving a stack frame holding the
157 * macro value execution context, which then gets the result of the
162 ao_scheme_eval_formal(void)
165 struct ao_scheme_stack *prev;
167 DBGI("formal: "); DBG_POLY(ao_scheme_v); DBG("\n");
169 /* Check what kind of function we've got */
170 if (!ao_scheme_stack->values) {
171 switch (func_type(ao_scheme_v)) {
172 case AO_SCHEME_FUNC_LAMBDA:
175 case AO_SCHEME_FUNC_MACRO:
176 /* Evaluate the result once more */
177 ao_scheme_stack->state = eval_macro;
178 if (!ao_scheme_stack_push())
181 /* After the function returns, take that
182 * value and re-evaluate it
184 prev = ao_scheme_poly_stack(ao_scheme_stack->prev);
185 ao_scheme_stack->sexprs = prev->sexprs;
187 DBGI(".. start macro\n");
188 DBGI("\t.. sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
189 DBGI("\t.. values "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
192 /* fall through ... */
193 case AO_SCHEME_FUNC_NLAMBDA:
194 DBGI(".. nlambda or macro\n");
196 /* use the raw sexprs as values */
197 ao_scheme_stack->values = ao_scheme_stack->sexprs;
198 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
199 ao_scheme_stack->state = eval_exec;
201 /* ready to execute now */
208 /* Append formal to list of values */
209 formal = ao_scheme__cons(ao_scheme_v, AO_SCHEME_NIL);
213 if (ao_scheme_stack->values_tail)
214 ao_scheme_poly_cons(ao_scheme_stack->values_tail)->cdr = formal;
216 ao_scheme_stack->values = formal;
217 ao_scheme_stack->values_tail = formal;
219 DBGI(".. values "); DBG_POLY(ao_scheme_stack->values); DBG("\n");
222 * Step to the next argument, if this is last, then
223 * 'sexpr' will end up switching to 'exec'
225 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
227 ao_scheme_stack->state = eval_sexpr;
229 DBGI(".. "); DBG_POLY(ao_scheme_v); DBG("\n");
234 * Start executing a function call
236 * Most builtins are easy, just call the function.
237 * 'cond' is magic; it sticks the list of clauses
238 * in 'sexprs' and switches to 'cond' state. That
239 * bit of magic is done in ao_scheme_set_cond.
241 * Lambdas build a new frame to hold the locals and
242 * then re-use the current stack context to evaluate
243 * the s-expression from the lambda.
247 ao_scheme_eval_exec(void)
250 struct ao_scheme_builtin *builtin;
252 DBGI("exec: "); DBG_POLY(ao_scheme_v); DBG(" values "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
253 ao_scheme_stack->sexprs = AO_SCHEME_NIL;
254 switch (ao_scheme_poly_type(ao_scheme_v)) {
255 case AO_SCHEME_BUILTIN:
256 ao_scheme_stack->state = eval_val;
257 builtin = ao_scheme_poly_builtin(ao_scheme_v);
258 v = ao_scheme_func(builtin) (
259 ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->values)->cdr));
260 DBG_DO(if (!ao_scheme_exception && ao_scheme_poly_builtin(ao_scheme_v)->func == builtin_set) {
261 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
262 ao_poly atom = ao_scheme_arg(cons, 1);
263 ao_poly val = ao_scheme_arg(cons, 2);
264 DBGI("set "); DBG_POLY(atom); DBG(" = "); DBG_POLY(val); DBG("\n");
266 builtin = ao_scheme_poly_builtin(ao_scheme_v);
267 if (builtin && (builtin->args & AO_SCHEME_FUNC_FREE_ARGS) && !ao_scheme_stack_marked(ao_scheme_stack)) {
268 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_stack->values);
269 ao_scheme_stack->values = AO_SCHEME_NIL;
270 ao_scheme_cons_free(cons);
274 ao_scheme_stack->values = AO_SCHEME_NIL;
275 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
276 DBGI(".. result "); DBG_POLY(ao_scheme_v); DBG ("\n");
277 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
279 case AO_SCHEME_LAMBDA:
280 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
281 ao_scheme_stack->state = eval_begin;
282 v = ao_scheme_lambda_eval();
283 ao_scheme_stack->sexprs = v;
284 ao_scheme_stack->values = AO_SCHEME_NIL;
285 ao_scheme_stack->values_tail = AO_SCHEME_NIL;
286 DBGI(".. sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
287 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
289 case AO_SCHEME_STACK:
290 DBGI(".. stack "); DBG_POLY(ao_scheme_v); DBG("\n");
291 ao_scheme_v = ao_scheme_stack_eval();
292 DBGI(".. value "); DBG_POLY(ao_scheme_v); DBG("\n");
293 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
300 * Finish setting up the apply evaluation
302 * The value is the list to execute
305 ao_scheme_eval_apply(void)
307 struct ao_scheme_cons *cons = ao_scheme_poly_cons(ao_scheme_v);
308 struct ao_scheme_cons *cdr, *prev;
310 /* Glue the arguments into the right shape. That's all but the last
311 * concatenated onto the last
316 cdr = ao_scheme_poly_cons(prev->cdr);
317 if (cdr->cdr == AO_SCHEME_NIL)
320 DBGI("before mangling: "); DBG_POLY(ao_scheme_v); DBG("\n");
321 prev->cdr = cdr->car;
322 ao_scheme_stack->values = ao_scheme_v;
323 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->values)->car;
324 DBGI("apply: "); DBG_POLY(ao_scheme_stack->values); DBG ("\n");
325 ao_scheme_stack->state = eval_exec;
326 ao_scheme_stack_mark(ao_scheme_stack);
331 * Start evaluating the next cond clause
333 * If the list of clauses is empty, then
334 * the result of the cond is nil.
336 * Otherwise, set the current stack state to 'cond_test' and create a
337 * new stack context to evaluate the test s-expression. Once that's
338 * complete, we'll land in 'cond_test' to finish the clause.
341 ao_scheme_eval_cond(void)
343 DBGI("cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
344 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
345 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
346 if (!ao_scheme_stack->sexprs) {
347 ao_scheme_v = _ao_scheme_bool_false;
348 ao_scheme_stack->state = eval_val;
350 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
351 if (!ao_scheme_v || !AO_SCHEME_IS_CONS(ao_scheme_v)) {
352 ao_scheme_error(AO_SCHEME_INVALID, "invalid cond clause");
355 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_v)->car;
356 if (ao_scheme_v == _ao_scheme_atom_else)
357 ao_scheme_v = _ao_scheme_bool_true;
358 ao_scheme_stack->state = eval_cond_test;
359 if (!ao_scheme_stack_push())
366 * Finish a cond clause.
368 * Check the value from the test expression, if
369 * non-nil, then set up to evaluate the value expression.
371 * Otherwise, step to the next clause and go back to the 'cond'
375 ao_scheme_eval_cond_test(void)
377 DBGI("cond_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
378 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
379 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
380 if (ao_scheme_v != _ao_scheme_bool_false) {
381 struct ao_scheme_cons *car = ao_scheme_poly_cons(ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car);
382 ao_poly c = car->cdr;
385 ao_scheme_stack->state = eval_begin;
386 ao_scheme_stack->sexprs = c;
388 ao_scheme_stack->state = eval_val;
390 ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
391 DBGI("next cond: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
392 ao_scheme_stack->state = eval_cond;
398 * Evaluate a list of sexprs, returning the value from the last one.
400 * ao_scheme_begin records the list in stack->sexprs, so we just need to
401 * walk that list. Set ao_scheme_v to the car of the list and jump to
402 * eval_sexpr. When that's done, it will land in eval_val. For all but
403 * the last, leave a stack frame with eval_begin set so that we come
404 * back here. For the last, don't add a stack frame so that we can
408 ao_scheme_eval_begin(void)
410 DBGI("begin: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
411 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
412 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
414 if (!ao_scheme_stack->sexprs) {
415 ao_scheme_v = AO_SCHEME_NIL;
416 ao_scheme_stack->state = eval_val;
418 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
419 ao_scheme_stack->sexprs = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
421 /* If there are more sexprs to do, then come back here, otherwise
422 * return the value of the last one by just landing in eval_sexpr
424 if (ao_scheme_stack->sexprs) {
425 ao_scheme_stack->state = eval_begin;
426 if (!ao_scheme_stack_push())
429 ao_scheme_stack->state = eval_sexpr;
435 * Conditionally execute a list of sexprs while the first is true
438 ao_scheme_eval_while(void)
440 DBGI("while: "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
441 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
442 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
444 ao_scheme_stack->values = ao_scheme_v;
445 if (!ao_scheme_stack->sexprs) {
446 ao_scheme_v = AO_SCHEME_NIL;
447 ao_scheme_stack->state = eval_val;
449 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->car;
450 ao_scheme_stack->state = eval_while_test;
451 if (!ao_scheme_stack_push())
458 * Check the while condition, terminate the loop if nil. Otherwise keep going
461 ao_scheme_eval_while_test(void)
463 DBGI("while_test: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
464 DBGI(".. frame "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");
465 DBGI(".. saved frame "); DBG_POLY(ao_scheme_stack->frame); DBG("\n");
467 if (ao_scheme_v != _ao_scheme_bool_false) {
468 ao_scheme_stack->values = ao_scheme_v;
469 ao_scheme_v = ao_scheme_poly_cons(ao_scheme_stack->sexprs)->cdr;
470 ao_scheme_stack->state = eval_while;
471 if (!ao_scheme_stack_push())
473 ao_scheme_stack->state = eval_begin;
474 ao_scheme_stack->sexprs = ao_scheme_v;
478 ao_scheme_stack->state = eval_val;
479 ao_scheme_v = ao_scheme_stack->values;
485 * Replace the original sexpr with the macro expansion, then
489 ao_scheme_eval_macro(void)
491 DBGI("macro: "); DBG_POLY(ao_scheme_v); DBG(" sexprs "); DBG_POLY(ao_scheme_stack->sexprs); DBG("\n");
493 if (ao_scheme_v == AO_SCHEME_NIL)
495 if (AO_SCHEME_IS_CONS(ao_scheme_v)) {
496 *ao_scheme_poly_cons(ao_scheme_stack->sexprs) = *ao_scheme_poly_cons(ao_scheme_v);
497 ao_scheme_v = ao_scheme_stack->sexprs;
498 DBGI("sexprs rewritten to: "); DBG_POLY(ao_scheme_v); DBG("\n");
500 ao_scheme_stack->sexprs = AO_SCHEME_NIL;
501 ao_scheme_stack->state = eval_sexpr;
505 static int (*const evals[])(void) = {
506 [eval_sexpr] = ao_scheme_eval_sexpr,
507 [eval_val] = ao_scheme_eval_val,
508 [eval_formal] = ao_scheme_eval_formal,
509 [eval_exec] = ao_scheme_eval_exec,
510 [eval_apply] = ao_scheme_eval_apply,
511 [eval_cond] = ao_scheme_eval_cond,
512 [eval_cond_test] = ao_scheme_eval_cond_test,
513 [eval_begin] = ao_scheme_eval_begin,
514 [eval_while] = ao_scheme_eval_while,
515 [eval_while_test] = ao_scheme_eval_while_test,
516 [eval_macro] = ao_scheme_eval_macro,
519 const char * const ao_scheme_state_names[] = {
520 [eval_sexpr] = "sexpr",
522 [eval_formal] = "formal",
523 [eval_exec] = "exec",
524 [eval_apply] = "apply",
525 [eval_cond] = "cond",
526 [eval_cond_test] = "cond_test",
527 [eval_begin] = "begin",
528 [eval_while] = "while",
529 [eval_while_test] = "while_test",
530 [eval_macro] = "macro",
534 * Called at restore time to reset all execution state
538 ao_scheme_eval_clear_globals(void)
540 ao_scheme_stack = NULL;
541 ao_scheme_frame_current = NULL;
542 ao_scheme_v = AO_SCHEME_NIL;
546 ao_scheme_eval_restart(void)
548 return ao_scheme_stack_push();
552 ao_scheme_eval(ao_poly _v)
556 ao_scheme_frame_init();
558 if (!ao_scheme_stack_push())
559 return AO_SCHEME_NIL;
561 while (ao_scheme_stack) {
562 if (!(*evals[ao_scheme_stack->state])() || ao_scheme_exception) {
563 ao_scheme_stack_clear();
564 return AO_SCHEME_NIL;
567 DBG_DO(if (ao_scheme_frame_current) {DBGI("frame left as "); DBG_POLY(ao_scheme_frame_poly(ao_scheme_frame_current)); DBG("\n");});
568 ao_scheme_frame_current = NULL;