causa-arcana-misc
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lesson-lisp
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Deeper lookup

This commit is contained in:
Alex Kotov 2023-05-07 18:43:08 +04:00
parent fccc3b4f8c
commit 730d2ff638
Signed by: kotovalexarian
GPG Key ID: 553C0EBBEB5D5F08
1 changed files with 20 additions and 12 deletions
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32
src/eval.c
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@ -9,7 +9,7 @@
#include <stddef.h>
#include <string.h>
static struct Object *lookup(struct Object *namespace, struct Object *name);
static struct Object *lookup(struct Object *environment, struct Object *name);
static struct Object *eval_list(
struct Object *object,
@ -21,13 +21,12 @@ struct Object *eval(
struct Object *const environment
) {
assert(Object_is_pair(environment));
assert(OBJECT_IS_NULL(environment->pair.cdr));
// NULL is an empty list, can't eval
assert(!OBJECT_IS_NULL(object));
// SYMBOL performs lookup
if (Object_is_symbol(object)) return lookup(environment->pair.car, object);
if (Object_is_symbol(object)) return lookup(environment, object);
// Almost everything evaluates to itself
if (!Object_is_pair(object)) return object;
@ -77,18 +76,27 @@ struct Object *eval_list(
}
}
struct Object *lookup(struct Object *namespace, struct Object *const name)
struct Object *lookup(struct Object *environment, struct Object *const name)
{
assert(OBJECT_IS_LIST_HEAD(namespace));
assert(OBJECT_IS_LIST_HEAD(environment));
assert(Object_is_symbol(name));
while (!OBJECT_IS_NULL(namespace)) {
assert(Object_is_pair(namespace));
struct Object *const item = namespace->pair.car;
assert(Object_is_pair(item));
assert(Object_is_symbol(item->pair.car));
if (strcmp(item->pair.car->s, name->s) == 0) return item->pair.cdr;
namespace = namespace->pair.cdr;
while (!OBJECT_IS_NULL(environment)) {
assert(Object_is_pair(environment));
struct Object *namespace = environment->pair.car;
while (!OBJECT_IS_NULL(namespace)) {
assert(Object_is_pair(namespace));
struct Object *const item = namespace->pair.car;
assert(Object_is_pair(item));
assert(Object_is_symbol(item->pair.car));
if (strcmp(item->pair.car->s, name->s) == 0) return item->pair.cdr;
namespace = namespace->pair.cdr;
}
environment = environment->pair.cdr;
}
struct Object *const builtin_procedure = builtins_get(name->s);