causa-arcana-misc/lesson-lisp
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eval

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This commit is contained in:
Alex Kotov 2023-05-04 01:25:40 +04:00
parent d35acd96af
commit 2213a40c02
Signed by: kotovalexarian
GPG key ID: 553C0EBBEB5D5F08
1 changed files with 67 additions and 1 deletions
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68
main.c
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@ -71,6 +71,14 @@ static struct Object *expr();
static struct Object *parens();
static struct Object *parens_part();
/********
* Eval *
********/
static struct Object *eval(struct Object *program);
static struct Object *func_sum(struct Object *numbers);
/*******************
* Implementations *
*******************/
@ -89,6 +97,7 @@ int main()
}
struct Object *const program = parse();
struct Object *const result = eval(program);
exit(EXIT_SUCCESS);
}
@ -357,7 +366,7 @@ struct Object *expr()
case STATE_NUM:
{
struct Object *const object = prepare_object(TYPE_NUMBER);
object->s = tokens->val;
object->i = atoll(tokens->val);
shift_token();
return object;
}
@ -391,3 +400,60 @@ struct Object *parens_part()
return object;
}
/********
* Eval *
********/
struct Object *eval(struct Object *const program)
{
if (program->type != TYPE_PAIR) {
error("eval expects pair");
return NULL;
}
if (!program->a || program->a->type != TYPE_ATOM) {
error("eval expects atom");
return NULL;
}
if (strcmp(program->a->s, "sum") != 0) {
error("unknown func");
return NULL;
}
return func_sum(program->b);
}
struct Object *func_sum(struct Object *const numbers)
{
struct Object *const object = prepare_object(TYPE_NUMBER);
object->i = 0;
if (numbers) {
if (numbers->type == TYPE_NUMBER) {
object->i = numbers->i;
} else if (numbers->type == TYPE_PAIR) {
if (numbers->a->type != TYPE_NUMBER) {
error("type error");
return NULL;
}
object->i = numbers->a->i;
struct Object *b = eval(numbers->b);
if (numbers->b->type != TYPE_NUMBER) {
error("type error");
return NULL;
}
object->i += b->i;
} else {
error("type error");
return NULL;
}
}
return object;
}