diff --git a/lambda-ast.cabal b/lambda-ast.cabal
--- a/lambda-ast.cabal
+++ b/lambda-ast.cabal
@@ -1,7 +1,7 @@
 category:               Compilers/Interpreters
 copyright:              (c) 2012 Jonathan Fischoff 
 name:                   lambda-ast
-version:                0.0.1
+version:                0.0.4
 license:                BSD3
 license-file:           LICENSE
 author:                 Jonathan Fischoff
diff --git a/src/Language/Lambda/AST.hs b/src/Language/Lambda/AST.hs
--- a/src/Language/Lambda/AST.hs
+++ b/src/Language/Lambda/AST.hs
@@ -1,11 +1,13 @@
+{-# LANGUAGE DeriveDataTypeable #-}
 {- | An Untyped Lambda Calculus AST -}
 module Language.Lambda.AST where
+import Data.Data
 
 -- | A polymorphic version of the AST to allow different symbol types
 data GExpr a = Var a
              | App (GExpr a) (GExpr a)
              | Lam a         (GExpr a)
-     deriving(Show, Eq)
+     deriving(Show, Eq, Data, Typeable)
              
 -- | A common symbol type choice
 type Sym  = String