From 33b3d80c2dcd12dbf692984e0d736bfa9906a8b5 Mon Sep 17 00:00:00 2001
From: Felix Perktold <Felix.Perktold@student.uibk.ac.at>
Date: Sun, 21 Dec 2025 23:28:15 +0100
Subject: fix bug in apply, improve printing

---
 lisp.c | 17 +++++++++++------
 lisp.h |  2 +-
 lisp.y |  6 ++++--
 main.c |  2 +-
 4 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/lisp.c b/lisp.c
index 22e90b5..da0a5f6 100644
--- a/lisp.c
+++ b/lisp.c
@@ -265,21 +265,26 @@ value *eval_pair(env *e, value *v) {
 	}
 
 	if (head_eval->type == VT_LAMBDA) {
-		return apply(head_eval, tail);
+		return apply(e, head_eval, tail);
 	}
 
 	return v;
 }
 
-value *apply(value *lval, value *args) {
-	env *sub_env = env_create(lval->as.lambda.env);
+value *apply(env *e, value *lval, value *args) {
+	env *sub_env = env_create(e);
 	value *params = lval->as.lambda.params;
 	value *arg = args;
 
 	while (params->type == VT_PAIR && arg->type == VT_PAIR) {
-		env_define(sub_env,
-			   car(params)->as.sym,
-			   eval(lval->as.lambda.env, car(arg)));
+		if (car(params)->type != VT_SYMBOL) {
+			printf("not a symbol: ");
+			println_value(car(params));
+			return make_nil();
+		}
+
+		value *arg_eval = eval(e, car(arg));
+		env_define(sub_env, car(params)->as.sym, arg_eval);
 		params = cdr(params);
 		arg = cdr(arg);
 	}
diff --git a/lisp.h b/lisp.h
index 2e95fb9..5abdfd4 100644
--- a/lisp.h
+++ b/lisp.h
@@ -68,7 +68,7 @@ extern env *global_env;
 value *eval(env *e, value *val);
 value *eval_pair(env *e, value *val);
 
-value *apply(value *lambda, value *args);
+value *apply(env *e, value *lambda, value *args);
 
 value *builtin_cons(env *e, value *args);
 value *builtin_car(env *e, value *args);
diff --git a/lisp.y b/lisp.y
index 734bfa2..ffb9bf9 100644
--- a/lisp.y
+++ b/lisp.y
@@ -25,13 +25,15 @@ int yyerror(const char *s);
 %%
 sexprs: sexpr
       {
+        value *v = eval(global_env, $1);
         printf(";> ");
-        println_value(eval(global_env, $1));
+        println_value(v);
       }
       | sexprs sexpr
       {
+        value *v = eval(global_env, $2);
         printf(";> ");
-        println_value(eval(global_env, $2));
+        println_value(v);
       };
 
 sexpr:  atom
diff --git a/main.c b/main.c
index f297402..563d98a 100644
--- a/main.c
+++ b/main.c
@@ -23,7 +23,7 @@ int main(void) {
 	env_define(global_env, "<=", make_builtin(builtin_le));
 	// START REPL
 	char* line;
-	while ((line = readline("λ > ")) != NULL) {
+	while ((line = readline("λ> ")) != NULL) {
 		if (*line) {
 			add_history(line);
 		}
-- 
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