Fix ', add if and = along with bools

kr/src/ast.rs

@@ -1,15 +1,23 @@
 use std::rc::Rc;
 
-#[derive(Debug)]
+#[derive(Debug, Eq, PartialEq)]
 pub enum Form {
+    Nil,
     Int(i32),
+    Bool(bool),
     Symbol(String),
     Pair(Rc<Form>,Rc<Form>),
-    DeriComb { se: Rc<Form>, de: Option<String>, params: Rc<Form>, body: Rc<Form> },
     PrimComb(String, fn(Rc<Form>, Rc<Form>) -> Rc<Form>),
-    Nil,
+    DeriComb { se: Rc<Form>, de: Option<String>, params: Rc<Form>, body: Rc<Form> },
 }
 impl Form {
+    pub fn truthy(&self) -> bool {
+        match self {
+            Form::Bool(b) => *b,
+            Form::Nil     => false,
+            _             => true,
+        }
+    }
     pub fn int(&self) -> Option<i32> {
         match self {
             Form::Int(i) => Some(*i),