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add if special form

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This commit is contained in:
Sami Samhuri 2011-04-22 00:05:09 -07:00
parent 42f982f9ef
commit 684cbe7939
1 changed files with 18 additions and 2 deletions
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20
src/eval.c
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@ -22,7 +22,7 @@ static void init_special_form_handlers(void);
static void invalid_special_form(LakeList *expr, char *detail)
{
ERR("unrecognized special form, %s: %s", detail, repr(VAL(expr)));
ERR("malformed special form, %s: %s", detail, repr(VAL(expr)));
}
/* expr begins with the symbol "quote" so the quoted value is the 2nd value */
@ -146,6 +146,22 @@ static LakeVal *lambda_special_form(Env *env, LakeList *expr)
}
}
static LakeVal *if_special_form(Env *env, LakeList *expr)
{
if (LIST_N(expr) < 3) {
invalid_special_form(expr, "if requires 3 parameters");
return NULL;
}
list_shift(expr); /* "if" token */
LakeVal *cond = eval(env, list_shift(expr));
if (IS_TRUTHY(cond)) {
return eval(env, list_shift(expr));
}
else {
return eval(env, LIST_VAL(expr, 1));
}
}
static void init_special_form_handlers(void)
{
#define HANDLER(name, fn) g_hash_table_insert(special_form_handlers, \
@ -157,7 +173,7 @@ static void init_special_form_handlers(void)
HANDLER("quote", &quote_special_form);
HANDLER("and", &and_special_form);
HANDLER("or", &or_special_form);
/* HANDLER("if", &if_special_form); */
HANDLER("if", &if_special_form);
/* HANDLER("cond", &cond_special_form); */
HANDLER("set!", &setB_special_form);
HANDLER("define", &define_special_form);