From 91d683a1b819a5b720b9eb11f8409dff9c7883e1 Mon Sep 17 00:00:00 2001
From: Felix Perktold <Felix.Perktold@student.uibk.ac.at>
Date: Mon, 22 Dec 2025 13:06:02 +0100
Subject: tweaks

---
 lisp.c | 22 +++++++++++-----------
 lisp.h |  2 +-
 main.c |  2 +-
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/lisp.c b/lisp.c
index 5f5a6fb..b880eb3 100644
--- a/lisp.c
+++ b/lisp.c
@@ -69,19 +69,19 @@ value *cons(value *car, value *cdr) {
 }
 
 value *car(value *cons) {
-	if (cons->type == VT_PAIR) {
+	if (cons && cons->type == VT_PAIR) {
 		return cons->as.pair.car;
 	}
-	printf("not a pair: ");
+	printf("car of non-pair: ");
 	println_value(cons);
 	return make_nil();
 }	
 
 value *cdr(value *cons) {
-	if (cons->type == VT_PAIR) {
+	if (cons && cons->type == VT_PAIR) {
 		return cons->as.pair.cdr;
 	}
-	printf("not a pair: ");
+	printf("cdr of non-pair: ");
 	println_value(cons);
 	return make_nil();
 }	
@@ -194,9 +194,9 @@ value *eval(env *e, value *v) {
 	//printf("evaluating: ");
 	//print_value(v);
 	//printf("\n");
-
-	if (v->type == VT_NIL) {
-		return v;
+	
+	if (!v || v->type == VT_NIL) {
+		return make_nil();
 	}
 
 	if (v->type == VT_PAIR) {
@@ -231,7 +231,7 @@ value *eval_pair(env *e, value *v) {
 		if (defname->type != VT_SYMBOL) {
 			printf("error, expected symbol, found: ");
 			println_value(defname);
-			return v;
+			return make_nil();
 		}
 		env_define(e, defname->as.sym, defval);
 		return defval;
@@ -275,7 +275,7 @@ value *eval_pair(env *e, value *v) {
 }
 
 value *apply(env *e, value *lval, value *args) {
-	env *sub_env = env_create(e);
+	env *sub_env = env_create(lval->as.lambda.env);
 	value *params = lval->as.lambda.params;
 	value *arg = args;
 
@@ -409,7 +409,7 @@ value *builtin_div(env *e, value *args) {
 	return apply_to_nums(e, args, div_fn);
 }
 
-value *builtin_le(env *e, value *args) {
+value *builtin_lt(env *e, value *args) {
 	double prev_num;
 	value *v = eval(e, car(args));
 
@@ -436,7 +436,7 @@ value *builtin_le(env *e, value *args) {
 			println_value(v);
 			return make_nil();
 		}
-		if(prev_num > cur_num) {
+		if(prev_num >= cur_num) {
 			return make_nil();
 		}
 		prev_num = cur_num;
diff --git a/lisp.h b/lisp.h
index 7c9dd79..162da09 100644
--- a/lisp.h
+++ b/lisp.h
@@ -79,7 +79,7 @@ value *builtin_add(env *e, value *args);
 value *builtin_sub(env *e, value *args);
 value *builtin_mul(env *e, value *args);
 value *builtin_div(env *e, value *args);
-value *builtin_le(env *e, value *args);
+value *builtin_lt(env *e, value *args);
 
 int is_integer(double x);
 
diff --git a/main.c b/main.c
index 4f00b5d..2d258af 100644
--- a/main.c
+++ b/main.c
@@ -37,7 +37,7 @@ int main(int argc, char **argv) {
 	env_define(global_env, "-", make_builtin(builtin_sub));
 	env_define(global_env, "*", make_builtin(builtin_mul));
 	env_define(global_env, "/", make_builtin(builtin_div));
-	env_define(global_env, "<=", make_builtin(builtin_le));
+	env_define(global_env, "<", make_builtin(builtin_lt));
 
 	// evaluate files
 	for(int i = 1; i < argc; i++) {
-- 
cgit v1.2.3