add bool var toggle function

Signed-off-by: Ava Hahn <ava@aidanis.online>

tests/test_vars.rs

@@ -40,6 +40,43 @@ mod var_lib_tests {
         }
     }
 
+    #[test]
+    fn test_func_def_and_lookup() {
+        let doc1 = "(def test (hello) hello)";
+        let doc2 = "(test '1')";
+        let result = "1";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+
+        if let Ok(tree) = lex(&doc1.to_string()) {
+            let eval_result = *eval(&tree, &mut syms).unwrap();
+            if let Ctr::None = eval_result {
+                // pass
+            } else {
+                eprintln!("bad: {eval_result}");
+                assert!(false);
+            }
+        } else {
+            eprintln!("couldn't lex doc1");
+            assert!(false);
+        }
+
+        if let Ok(tree) = lex(&doc2.to_string()) {
+            let eval_result = *eval(&tree, &mut syms).unwrap();
+            if let Ctr::String(ref i) = eval_result {
+                assert_eq!(i.to_string(), result);
+            } else {
+                eprintln!("bad: {eval_result}");
+                assert!(false);
+            }
+        } else {
+            eprintln!("couldn't lex doc2");
+            assert!(false);
+        }
+    }
+
     #[test]
     fn test_variable_def_redef_and_lookup() {
         let doc1 = "(def test 1)";