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#include "eval.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "error.h"
void free_rules_until(fuspel* new, fuspel* old) {
while (new != old) {
free_rewrite_rule(&new->rule);
new = new->rest;
}
}
fuspel* match_expr(fuspel* rules, expression* to_match, expression* expr) {
if (to_match->kind != EXPR_NAME) {
expr = eval_rnf(rules, expr);
if (!expr)
return NULL;
}
switch (to_match->kind) {
case EXPR_NAME:
rules = push_fuspel(rules);
rules->rule.name = malloc(strlen(to_match->var1) + 1);
if (!rules->rule.name)
error_no_mem();
strcpy(rules->rule.name, to_match->var1);
rules->rule.args = NULL;
cpy_expression(&rules->rule.rhs, expr);
return rules;
case EXPR_INT:
;unsigned matches = eq_expression(to_match, expr);
free_expression(expr);
free(expr);
return matches ? rules : NULL;
case EXPR_LIST:
if (!to_match->var1) { // empty list
unsigned matches = eq_expression(to_match, expr);
free_expression(expr);
free(expr);
return matches ? rules : NULL;
}
case EXPR_TUPLE:
;fuspel* _rules = match_expr(rules, to_match->var1, expr->var1);
if (!_rules) {
free_expression(expr);
free(expr);
return NULL;
}
fuspel* __rules = match_expr(_rules, to_match->var2, expr->var2);
if (!__rules)
free_rules_until(_rules, rules);
free_expression(expr);
free(expr);
return __rules;
default:
free_expression(expr);
free(expr);
return NULL;
}
}
fuspel* match_rule(fuspel* rules, rewrite_rule* rule, expression* expr) {
switch (expr->kind) {
case EXPR_NAME:
return (!strcmp(expr->var1, rule->name) &&
empty_args_list(rule->args)) ? rules : NULL;
case EXPR_APP:
;expression** expr_args = flatten_app_args(expr);
unsigned char i = 0;
if (!strcmp(expr_args[0]->var1, rule->name)) {
expression* _expr = expr_args[++i];
arg_list* args = rule->args;
fuspel* _rules = rules;
while (!empty_args_list(args)) {
fuspel* __rules = match_expr(_rules, &args->elem, _expr);
if (!__rules) {
free_rules_until(_rules, rules);
free(expr_args);
return NULL;
}
_rules = __rules;
args = args->rest;
_expr = expr_args[++i];
if (!empty_args_list(args) && !_expr) {
free_rules_until(_rules, rules);
return NULL;
}
}
free(expr_args);
return _rules;
}
default:
return NULL;
}
}
unsigned apply(expression* result, rewrite_rule* rule, expression* expr) {
switch (expr->kind) {
case EXPR_NAME:
cpy_expression(result, &rule->rhs);
return 1;
break;
case EXPR_APP:
// TODO
default:
return 0;
}
}
expression* eval_rnf(fuspel* rules, expression* expr) {
expression* result = calloc(1, sizeof(expression));
if (!result)
error_no_mem();
expression *e1, *e2;
fuspel* _rules = rules;
fuspel* new_rules;
switch (expr->kind) {
case EXPR_INT:
case EXPR_TUPLE:
case EXPR_LIST:
cpy_expression(result, expr);
break;
case EXPR_NAME:
case EXPR_APP:
while (_rules) {
new_rules = match_rule(rules, &_rules->rule, expr);
if (new_rules) {
rules = new_rules;
result = eval_rnf(rules, &_rules->rule.rhs);
free_rules_until(new_rules, _rules);
return result;
}
_rules = _rules->rest;
}
cpy_expression(result, expr);
break;
}
return result;
}
expression* eval(fuspel* rules, expression* expr) {
expression* result = calloc(1, sizeof(expression));
if (!result)
error_no_mem();
expression *e1, *e2;
fuspel* _rules = rules;
fuspel* new_rules;
switch (expr->kind) {
case EXPR_INT:
cpy_expression(result, expr);
break;
case EXPR_NAME:
case EXPR_APP:
while (_rules) {
new_rules = match_rule(rules, &_rules->rule, expr);
if (new_rules) {
rules = new_rules;
result = eval(new_rules, &_rules->rule.rhs);
free_rules_until(new_rules, rules);
return result;
}
_rules = _rules->rest;
}
cpy_expression(result, expr);
break;
case EXPR_LIST:
if (!expr->var1) {
cpy_expression(result, expr);
break;
}
case EXPR_TUPLE:
e1 = eval(rules, expr->var1);
e2 = eval(rules, expr->var2);
result->kind = expr->kind;
result->var1 = e1;
result->var2 = e2;
break;
}
return result;
}
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