tisp

commit 46b48386b50707c4db43b1a5560c1dc01ab46943
parent 0a79a514a0e4fc5bfccb611cfd4522f422318e02
Author: Ed van Bruggen <edvb@uw.edu>
Date:   Sun, 23 Dec 2018 19:49:55 -0800

Add NONE type for returning no value

Diffstat:
tisp.c
 | 
10
++++++++--
tisp.h
 | 
3
++-

2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/tisp.c b/tisp.c
@@ -52,6 +52,7 @@ char *
 type_str(Type t)
 {
 	switch (t) {
+	case NONE:      return "none";
 	case NIL:       return "nil";
 	case INTEGER:   return "integer";
 	case DOUBLE:    return "double";
@@ -555,6 +556,7 @@ tisp_eval(Env env, Val v)
 {
 	Val f, args;
 	switch (v->t) {
+	case NONE:
 	case NIL:
 	case INTEGER:
 	case DOUBLE:
@@ -593,6 +595,8 @@ void
 tisp_print(Val v)
 {
 	switch (v->t) {
+	case NONE:
+		break;
 	case NIL:
 		printf("()");
 		break;
@@ -727,7 +731,7 @@ prim_define(Env env, Val args)
 	if (!(v = tisp_eval(env, car(cdr(args)))))
 		return NULL;
 	hash_add(env->h, car(args)->v.s, v);
-	return NULL;
+	return env->none;
 }
 
 static Val
@@ -762,7 +766,7 @@ prim_load(Env env, Val args)
 	free(func);
 
 	env->libhc++;
-	return NULL;
+	return env->none;
 }
 
 void
@@ -777,6 +781,8 @@ tisp_env_init(size_t cap)
 	Env e = emalloc(sizeof(struct Env));
 	e->nil = emalloc(sizeof(struct Val));
 	e->nil->t = NIL;
+	e->none = emalloc(sizeof(struct Val));
+	e->none->t = NONE;
 	e->t = emalloc(sizeof(struct Val));
 	e->t->t = SYMBOL;
 	e->t->v.s = "t";
diff --git a/tisp.h b/tisp.h
@@ -68,6 +68,7 @@ typedef struct {
 } Pair;
 
 typedef enum {
+	NONE,
 	NIL,
 	INTEGER,
 	RATIONAL,
@@ -93,7 +94,7 @@ struct Val {
 };
 
 struct Env {
-	Val nil, t;
+	Val none, nil, t;
 	Hash h;
 	Hash strs;
 	void **libh;