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.
18 struct ao_lisp_stack *ao_lisp_stack;
20 uint8_t ao_lisp_skip_cons_free;
23 ao_lisp_set_cond(struct ao_lisp_cons *c)
25 ao_lisp_stack->state = eval_cond;
26 ao_lisp_stack->sexprs = ao_lisp_cons_poly(c);
31 func_type(ao_poly func)
33 if (func == AO_LISP_NIL)
34 return ao_lisp_error(AO_LISP_INVALID, "func is nil");
35 switch (ao_lisp_poly_type(func)) {
37 return ao_lisp_poly_builtin(func)->args & AO_LISP_FUNC_MASK;
39 return ao_lisp_poly_lambda(func)->args;
41 return AO_LISP_FUNC_LAMBDA;
43 ao_lisp_error(AO_LISP_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_lisp_eval_sexpr(void)
71 DBGI("sexpr: "); DBG_POLY(ao_lisp_v); DBG("\n");
72 switch (ao_lisp_poly_type(ao_lisp_v)) {
74 if (ao_lisp_v == AO_LISP_NIL) {
75 if (!ao_lisp_stack->values) {
77 * empty list evaluates to empty list
79 ao_lisp_v = AO_LISP_NIL;
80 ao_lisp_stack->state = eval_val;
83 * done with arguments, go execute it
85 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->values)->car;
86 ao_lisp_stack->state = eval_exec;
89 if (!ao_lisp_stack->values)
90 ao_lisp_stack->list = ao_lisp_v;
92 * Evaluate another argument and then switch
93 * to 'formal' to add the value to the values
96 ao_lisp_stack->sexprs = ao_lisp_v;
97 ao_lisp_stack->state = eval_formal;
98 if (!ao_lisp_stack_push())
101 * push will reset the state to 'sexpr', which
102 * will evaluate the expression
104 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_v)->car;
108 DBGI("..frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
109 ao_lisp_v = ao_lisp_atom_get(ao_lisp_v);
115 case AO_LISP_BUILTIN:
117 ao_lisp_stack->state = eval_val;
120 DBGI(".. result "); DBG_POLY(ao_lisp_v); DBG("\n");
125 * A value has been computed.
127 * If the value was computed from a macro,
128 * then we want to reset the current context
129 * to evaluate the macro result again.
131 * If not a macro, then pop the stack.
132 * If the stack is empty, we're done.
133 * Otherwise, the stack will contain
138 ao_lisp_eval_val(void)
140 DBGI("val: "); DBG_POLY(ao_lisp_v); DBG("\n");
142 * Value computed, pop the stack
143 * to figure out what to do with the value
146 DBGI("..state %d\n", ao_lisp_stack ? ao_lisp_stack->state : -1);
151 * A formal has been computed.
153 * If this is the first formal, then check to see if we've got a
154 * lamda/lexpr or macro/nlambda.
156 * For lambda/lexpr, go compute another formal. This will terminate
157 * when the sexpr state sees nil.
159 * For macro/nlambda, we're done, so move the sexprs into the values
162 * Macros have an additional step of saving a stack frame holding the
163 * macro value execution context, which then gets the result of the
168 ao_lisp_eval_formal(void)
171 struct ao_lisp_stack *prev;
173 DBGI("formal: "); DBG_POLY(ao_lisp_v); DBG("\n");
175 /* Check what kind of function we've got */
176 if (!ao_lisp_stack->values) {
177 switch (func_type(ao_lisp_v)) {
178 case AO_LISP_FUNC_LAMBDA:
179 case AO_LISP_FUNC_LEXPR:
180 DBGI(".. lambda or lexpr\n");
182 case AO_LISP_FUNC_MACRO:
183 /* Evaluate the result once more */
184 ao_lisp_stack->state = eval_macro;
185 if (!ao_lisp_stack_push())
188 /* After the function returns, take that
189 * value and re-evaluate it
191 prev = ao_lisp_poly_stack(ao_lisp_stack->prev);
192 ao_lisp_stack->sexprs = prev->sexprs;
194 DBGI(".. start macro\n");
195 DBGI(".. sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
196 DBGI(".. values "); DBG_POLY(ao_lisp_stack->values); DBG("\n");
199 /* fall through ... */
200 case AO_LISP_FUNC_NLAMBDA:
201 DBGI(".. nlambda or macro\n");
203 /* use the raw sexprs as values */
204 ao_lisp_stack->values = ao_lisp_stack->sexprs;
205 ao_lisp_stack->values_tail = AO_LISP_NIL;
206 ao_lisp_stack->state = eval_exec;
208 /* ready to execute now */
215 /* Append formal to list of values */
216 formal = ao_lisp__cons(ao_lisp_v, AO_LISP_NIL);
220 if (ao_lisp_stack->values_tail)
221 ao_lisp_poly_cons(ao_lisp_stack->values_tail)->cdr = formal;
223 ao_lisp_stack->values = formal;
224 ao_lisp_stack->values_tail = formal;
226 DBGI(".. values "); DBG_POLY(ao_lisp_stack->values); DBG("\n");
229 * Step to the next argument, if this is last, then
230 * 'sexpr' will end up switching to 'exec'
232 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->cdr;
234 ao_lisp_stack->state = eval_sexpr;
236 DBGI(".. "); DBG_POLY(ao_lisp_v); DBG("\n");
241 * Start executing a function call
243 * Most builtins are easy, just call the function.
244 * 'cond' is magic; it sticks the list of clauses
245 * in 'sexprs' and switches to 'cond' state. That
246 * bit of magic is done in ao_lisp_set_cond.
248 * Lambdas build a new frame to hold the locals and
249 * then re-use the current stack context to evaluate
250 * the s-expression from the lambda.
254 ao_lisp_eval_exec(void)
257 struct ao_lisp_builtin *builtin;
259 DBGI("exec: "); DBG_POLY(ao_lisp_v); DBG(" values "); DBG_POLY(ao_lisp_stack->values); DBG ("\n");
260 ao_lisp_stack->sexprs = AO_LISP_NIL;
261 switch (ao_lisp_poly_type(ao_lisp_v)) {
262 case AO_LISP_BUILTIN:
263 ao_lisp_stack->state = eval_val;
264 builtin = ao_lisp_poly_builtin(ao_lisp_v);
265 v = ao_lisp_func(builtin) (
266 ao_lisp_poly_cons(ao_lisp_poly_cons(ao_lisp_stack->values)->cdr));
267 DBG_DO(if (!ao_lisp_exception && ao_lisp_poly_builtin(ao_lisp_v)->func == builtin_set) {
268 struct ao_lisp_cons *cons = ao_lisp_poly_cons(ao_lisp_stack->values);
269 ao_poly atom = ao_lisp_arg(cons, 1);
270 ao_poly val = ao_lisp_arg(cons, 2);
271 DBGI("set "); DBG_POLY(atom); DBG(" = "); DBG_POLY(val); DBG("\n");
273 builtin = ao_lisp_poly_builtin(ao_lisp_v);
274 if (builtin && builtin->args & AO_LISP_FUNC_FREE_ARGS && !ao_lisp_stack_marked(ao_lisp_stack) && !ao_lisp_skip_cons_free)
275 ao_lisp_cons_free(ao_lisp_poly_cons(ao_lisp_stack->values));
278 ao_lisp_stack->values = AO_LISP_NIL;
279 ao_lisp_stack->values_tail = AO_LISP_NIL;
280 DBGI(".. result "); DBG_POLY(ao_lisp_v); DBG ("\n");
281 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
284 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
285 ao_lisp_stack->state = eval_progn;
286 v = ao_lisp_lambda_eval();
287 ao_lisp_stack->sexprs = v;
288 ao_lisp_stack->values = AO_LISP_NIL;
289 ao_lisp_stack->values_tail = AO_LISP_NIL;
290 DBGI(".. sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
291 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
294 DBGI(".. stack "); DBG_POLY(ao_lisp_v); DBG("\n");
295 ao_lisp_v = ao_lisp_stack_eval();
296 DBGI(".. value "); DBG_POLY(ao_lisp_v); DBG("\n");
297 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
300 ao_lisp_skip_cons_free = 0;
305 * Finish setting up the apply evaluation
307 * The value is the list to execute
310 ao_lisp_eval_apply(void)
312 struct ao_lisp_cons *cons = ao_lisp_poly_cons(ao_lisp_v);
313 struct ao_lisp_cons *cdr, *prev;
315 /* Glue the arguments into the right shape. That's all but the last
316 * concatenated onto the last
321 cdr = ao_lisp_poly_cons(prev->cdr);
322 if (cdr->cdr == AO_LISP_NIL)
325 DBGI("before mangling: "); DBG_POLY(ao_lisp_v); DBG("\n");
326 prev->cdr = cdr->car;
327 ao_lisp_stack->values = ao_lisp_v;
328 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->values)->car;
329 DBGI("apply: "); DBG_POLY(ao_lisp_stack->values); DBG ("\n");
330 ao_lisp_stack->state = eval_exec;
331 ao_lisp_skip_cons_free = 1;
336 * Start evaluating the next cond clause
338 * If the list of clauses is empty, then
339 * the result of the cond is nil.
341 * Otherwise, set the current stack state to 'cond_test' and create a
342 * new stack context to evaluate the test s-expression. Once that's
343 * complete, we'll land in 'cond_test' to finish the clause.
346 ao_lisp_eval_cond(void)
348 DBGI("cond: "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
349 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
350 DBGI(".. saved frame "); DBG_POLY(ao_lisp_stack->frame); DBG("\n");
351 if (!ao_lisp_stack->sexprs) {
352 ao_lisp_v = AO_LISP_NIL;
353 ao_lisp_stack->state = eval_val;
355 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->car;
356 if (!ao_lisp_v || ao_lisp_poly_type(ao_lisp_v) != AO_LISP_CONS) {
357 ao_lisp_error(AO_LISP_INVALID, "invalid cond clause");
360 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_v)->car;
361 if (ao_lisp_v == _ao_lisp_atom_else)
362 ao_lisp_v = _ao_lisp_bool_true;
363 ao_lisp_stack->state = eval_cond_test;
364 if (!ao_lisp_stack_push())
371 * Finish a cond clause.
373 * Check the value from the test expression, if
374 * non-nil, then set up to evaluate the value expression.
376 * Otherwise, step to the next clause and go back to the 'cond'
380 ao_lisp_eval_cond_test(void)
382 DBGI("cond_test: "); DBG_POLY(ao_lisp_v); DBG(" sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
383 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
384 DBGI(".. saved frame "); DBG_POLY(ao_lisp_stack->frame); DBG("\n");
385 if (ao_lisp_v != _ao_lisp_bool_false) {
386 struct ao_lisp_cons *car = ao_lisp_poly_cons(ao_lisp_poly_cons(ao_lisp_stack->sexprs)->car);
387 ao_poly c = car->cdr;
390 ao_lisp_stack->state = eval_progn;
391 ao_lisp_stack->sexprs = c;
393 ao_lisp_stack->state = eval_val;
395 ao_lisp_stack->sexprs = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->cdr;
396 DBGI("next cond: "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
397 ao_lisp_stack->state = eval_cond;
403 * Evaluate a list of sexprs, returning the value from the last one.
405 * ao_lisp_progn records the list in stack->sexprs, so we just need to
406 * walk that list. Set ao_lisp_v to the car of the list and jump to
407 * eval_sexpr. When that's done, it will land in eval_val. For all but
408 * the last, leave a stack frame with eval_progn set so that we come
409 * back here. For the last, don't add a stack frame so that we can
413 ao_lisp_eval_progn(void)
415 DBGI("progn: "); DBG_POLY(ao_lisp_v); DBG(" sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
416 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
417 DBGI(".. saved frame "); DBG_POLY(ao_lisp_stack->frame); DBG("\n");
419 if (!ao_lisp_stack->sexprs) {
420 ao_lisp_v = AO_LISP_NIL;
421 ao_lisp_stack->state = eval_val;
423 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->car;
424 ao_lisp_stack->sexprs = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->cdr;
426 /* If there are more sexprs to do, then come back here, otherwise
427 * return the value of the last one by just landing in eval_sexpr
429 if (ao_lisp_stack->sexprs) {
430 ao_lisp_stack->state = eval_progn;
431 if (!ao_lisp_stack_push())
434 ao_lisp_stack->state = eval_sexpr;
440 * Conditionally execute a list of sexprs while the first is true
443 ao_lisp_eval_while(void)
445 DBGI("while: "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
446 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
447 DBGI(".. saved frame "); DBG_POLY(ao_lisp_stack->frame); DBG("\n");
449 ao_lisp_stack->values = ao_lisp_v;
450 if (!ao_lisp_stack->sexprs) {
451 ao_lisp_v = AO_LISP_NIL;
452 ao_lisp_stack->state = eval_val;
454 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->car;
455 ao_lisp_stack->state = eval_while_test;
456 if (!ao_lisp_stack_push())
463 * Check the while condition, terminate the loop if nil. Otherwise keep going
466 ao_lisp_eval_while_test(void)
468 DBGI("while_test: "); DBG_POLY(ao_lisp_v); DBG(" sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
469 DBGI(".. frame "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");
470 DBGI(".. saved frame "); DBG_POLY(ao_lisp_stack->frame); DBG("\n");
472 if (ao_lisp_v != _ao_lisp_bool_false) {
473 ao_lisp_stack->values = ao_lisp_v;
474 ao_lisp_v = ao_lisp_poly_cons(ao_lisp_stack->sexprs)->cdr;
475 ao_lisp_stack->state = eval_while;
476 if (!ao_lisp_stack_push())
478 ao_lisp_stack->state = eval_progn;
479 ao_lisp_stack->sexprs = ao_lisp_v;
483 ao_lisp_stack->state = eval_val;
484 ao_lisp_v = ao_lisp_stack->values;
490 * Replace the original sexpr with the macro expansion, then
494 ao_lisp_eval_macro(void)
496 DBGI("macro: "); DBG_POLY(ao_lisp_v); DBG(" sexprs "); DBG_POLY(ao_lisp_stack->sexprs); DBG("\n");
498 if (ao_lisp_v == AO_LISP_NIL)
500 if (ao_lisp_poly_type(ao_lisp_v) == AO_LISP_CONS) {
501 *ao_lisp_poly_cons(ao_lisp_stack->sexprs) = *ao_lisp_poly_cons(ao_lisp_v);
502 ao_lisp_v = ao_lisp_stack->sexprs;
503 DBGI("sexprs rewritten to: "); DBG_POLY(ao_lisp_v); DBG("\n");
505 ao_lisp_stack->sexprs = AO_LISP_NIL;
506 ao_lisp_stack->state = eval_sexpr;
510 static int (*const evals[])(void) = {
511 [eval_sexpr] = ao_lisp_eval_sexpr,
512 [eval_val] = ao_lisp_eval_val,
513 [eval_formal] = ao_lisp_eval_formal,
514 [eval_exec] = ao_lisp_eval_exec,
515 [eval_apply] = ao_lisp_eval_apply,
516 [eval_cond] = ao_lisp_eval_cond,
517 [eval_cond_test] = ao_lisp_eval_cond_test,
518 [eval_progn] = ao_lisp_eval_progn,
519 [eval_while] = ao_lisp_eval_while,
520 [eval_while_test] = ao_lisp_eval_while_test,
521 [eval_macro] = ao_lisp_eval_macro,
524 const char *ao_lisp_state_names[] = {
525 [eval_sexpr] = "sexpr",
527 [eval_formal] = "formal",
528 [eval_exec] = "exec",
529 [eval_apply] = "apply",
530 [eval_cond] = "cond",
531 [eval_cond_test] = "cond_test",
532 [eval_progn] = "progn",
533 [eval_while] = "while",
534 [eval_while_test] = "while_test",
535 [eval_macro] = "macro",
539 * Called at restore time to reset all execution state
543 ao_lisp_eval_clear_globals(void)
545 ao_lisp_stack = NULL;
546 ao_lisp_frame_current = NULL;
547 ao_lisp_v = AO_LISP_NIL;
551 ao_lisp_eval_restart(void)
553 return ao_lisp_stack_push();
557 ao_lisp_eval(ao_poly _v)
561 if (!ao_lisp_stack_push())
564 while (ao_lisp_stack) {
565 if (!(*evals[ao_lisp_stack->state])() || ao_lisp_exception) {
566 ao_lisp_stack_clear();
570 DBG_DO(if (ao_lisp_frame_current) {DBGI("frame left as "); DBG_POLY(ao_lisp_frame_poly(ao_lisp_frame_current)); DBG("\n");});
571 ao_lisp_frame_current = NULL;