--- /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;
+uint8_t ao_scheme_skip_cons_free;
+
+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 */
+ case AO_SCHEME_BOOL:
+ case AO_SCHEME_INT:
+ case AO_SCHEME_BIGINT:
+ case AO_SCHEME_FLOAT:
+ case AO_SCHEME_STRING:
+ case AO_SCHEME_BUILTIN:
+ case AO_SCHEME_LAMBDA:
+ 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) && !ao_scheme_skip_cons_free) {
+ 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;
+ }
+ ao_scheme_skip_cons_free = 0;
+ 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_skip_cons_free = 1;
+ 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_v || ao_scheme_poly_type(ao_scheme_v) != AO_SCHEME_CONS) {
+ 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_poly_type(ao_scheme_v) == AO_SCHEME_CONS) {
+ *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;
+}
projects / fw / altos / blobdiff