From: Ramakrishnan Muthukrishnan <ram@rkrishnan.org>
Date: Mon, 22 Dec 2014 16:19:14 +0000 (+0530)
Subject: hw6: implement instance of Fractional for Stream Integer
X-Git-Url: https://git.rkrishnan.org/pf/content/%22file:/frontends/running.html?a=commitdiff_plain;h=dbe21fbd73c1806b851f0b9141596be2f0b59e29;p=yorgey.git

hw6: implement instance of Fractional for Stream Integer
---

diff --git a/hw6/Fibonacci.hs b/hw6/Fibonacci.hs
index 9a15712..e7b3f59 100644
--- a/hw6/Fibonacci.hs
+++ b/hw6/Fibonacci.hs
@@ -2,6 +2,7 @@
 {-# OPTIONS_GHC -fno-warn-missing-methods #-}
 {-# LANGUAGE InstanceSigs #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FlexibleContexts #-}
 module Fibonacci where
 
 -- exercise 1
@@ -86,3 +87,9 @@ instance Num (Stream Integer) where
   (+) (Cons x sx) (Cons y sy) = (Cons (x+y) ((+) sx sy))
   (*) :: Stream Integer -> Stream Integer -> Stream Integer
   (*) (Cons x sx) (Cons y sy) = Cons (x*y) ((streamMap (* x) sy) + sx*(Cons x sx))
+
+instance Fractional Integer => Fractional (Stream Integer) where
+  (/) :: Stream Integer -> Stream Integer -> Stream Integer
+  (/) (Cons x xs) (Cons y ys) = let r = streamMap (/ y) $ Cons x ((xs - r*ys))
+                                in
+                                  r