+++ /dev/null
-/*
- * 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;
-
-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)) {
- 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;
- }
- 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_stack_mark(ao_scheme_stack);
- 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_is_pair(ao_scheme_v)) {
- 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_is_cons(ao_scheme_v)) {
- *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;
-}
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