tisp

commit 8ae197462d5ad56470b72cebfedd8a9e3c9e5938
parent adc5c4e7b834c456ffaabec1ad1e4758d9592dd4
Author: Ed van Bruggen <edvb@uw.edu>
Date:   Thu, 15 Mar 2018 23:43:34 -0700

Use recursion instead of a loop for eval

Diffstat:
tisp.c
 | 
17
++---------------

1 file changed, 2 insertions(+), 15 deletions(-)
diff --git a/tisp.c b/tisp.c
@@ -424,7 +424,7 @@ eval_pair(Hash env, Val v)
 }
 
 static Val
-tisp_trampoline(Hash env, Val v, int *continu)
+tisp_eval(Hash env, Val v)
 {
 	Val f, args;
 	switch (v->t) {
@@ -433,24 +433,20 @@ tisp_trampoline(Hash env, Val v, int *continu)
 	case INTEGER:
 	case RATIONAL:
 	case STRING:
-		*continu = 0;
 		return v;
 	case SYMBOL:
-		*continu = 0;
 		return hash_get(env, v->v.s);
 	case PAIR:
 		f = tisp_eval(env, car(v));
 		args = eval_pair(env, cdr(v));
 		switch (f->t) {
 		case PRIMITIVE:
-			*continu = 0;
 			return (*f->v.pr)(env, args);
 		case FUNCTION:
 			/* tail call into the function body with the extended env */
 			hash_extend(env, f->v.f.args, args);
 			hash_merge(env, f->v.f.env);
-			*continu = 1;
-			return f->v.f.body;
+			return tisp_eval(env, f->v.f.body);
 		default:
 			die(1, "%s: Attempt to eval non primitive", argv0);
 		}
@@ -459,15 +455,6 @@ tisp_trampoline(Hash env, Val v, int *continu)
 	return v;
 }
 
-static Val
-tisp_eval(Hash env, Val v)
-{
-	int continu = 1;
-	while(continu)
-		v = tisp_trampoline(env, v, &continu);
-	return v;
-}
-
 /* TODO return str for error msgs? */
 static void
 tisp_print(Val v)