Implement basic derived calls, and fix eval not unvaling bug

kr/src/main.rs

@@ -37,10 +37,15 @@ fn parse_test() {
     }
     assert!(g.parse("((22)").is_err());
 }
+
 fn eval_test<T: Into<Form>>(gram: &grammar::TermParser, e: &Rc<Form>, code: &str, expected: T) {
     assert_eq!(*eval(Rc::clone(e), Rc::new(gram.parse(code).unwrap())), expected.into());
 }
 
+fn partial_eval_test<T: Into<Form>>(gram: &grammar::TermParser, e: &Rc<Form>, code: &str, expected: T) {
+    assert_eq!(*eval(Rc::clone(e), Rc::new(gram.parse(code).unwrap())), expected.into());
+}
+
 #[test]
 fn basic_eval_test() { let g = grammar::TermParser::new(); let e = root_env();
     eval_test(&g, &e, "(+ 2 (car (cons 4 '(1 2))))", 6);