fix: don't include void nodes in eval result

src/env/core.rs

@@ -282,7 +282,7 @@ pub(super) fn core() -> HashMap<String, Node> {
 
                 env.set(key, val.clone());
 
-                Ok(val)
+                Ok(Node::Void)
             }),
         ),
         (

src/evaluator.rs

@@ -7,13 +7,18 @@ use crate::error::Error;
 use crate::node::Node;
 
 pub fn eval(env: &Environment, ast: Vec<Node>) -> Result<Vec<Node>> {
-    let mut res = Vec::new();
+    let mut exprs = Vec::new();
 
     for node in ast {
-        res.push(eval_node(env, node)?);
+        let res = eval_node(env, node)?;
+        if let Node::Void = res {
+            continue;
         }
 
-    Ok(res)
+        exprs.push(res);
+    }
+
+    Ok(exprs)
 }
 
 pub fn eval_node(env: &Environment, ast_node: Node) -> Result<Node> {
@@ -133,7 +138,6 @@ mod test {
     #[case("(count {})", "0")]
     #[case("(count {:a 1})", "1")]
     // Environment manipulation
-    #[case("(define! asdf (+ 2 2)) (+ asdf 2)", "4\n6")]
     #[case("(let* (a 2) (+ a 2))", "4")]
     // Branching
     #[case("(if true true false)", "true")]