From 04036d0605e95c06f5d6dea11c2618267c059550 Mon Sep 17 00:00:00 2001
From: Ramakrishnan Muthukrishnan <ram@rkrishnan.org>
Date: Sun, 21 Dec 2014 17:37:24 +0530
Subject: [PATCH] hw5: exercise 3

---
 hw5/Calc.hs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw5/Calc.hs b/hw5/Calc.hs
index ef4fd2e..46f7820 100644
--- a/hw5/Calc.hs
+++ b/hw5/Calc.hs
@@ -18,3 +18,13 @@ evalStr :: String -> Maybe Integer
 --               Just e -> Just (eval e)
 --              Nothing -> Nothing
 evalStr s = fmap eval (parseExp Lit Add Mul s)
+
+class Expr a where
+  lit :: Integer -> a
+  add :: a -> a -> a
+  mul :: a -> a -> a
+
+instance Expr ExprT where
+  lit = Lit
+  add = Add
+  mul = Mul
-- 
2.45.2