From 3db17331b1d1308f8d9ceb336d1bfef7a91fadc5 Mon Sep 17 00:00:00 2001
From: "Michael G. Sloan" <mgsloan@gmail.com>
Date: Sun, 22 Jul 2007 22:53:37 +0200
Subject: Cleanup of shift code

darcs-hash:20070722205337-0d649-35419b898df5fc30d9a48bde46f8ede66e39c009
---
 StackSet.hs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/StackSet.hs b/StackSet.hs
index 037b124..265359c 100644
--- a/StackSet.hs
+++ b/StackSet.hs
@@ -487,7 +487,7 @@ swapMaster = modify' $ \c -> case c of
 -- element on the current stack, the original stackSet is returned.
 --
 shift :: (Ord a, Eq s, Integral i) => i -> StackSet i a s sd -> StackSet i a s sd
-shift n s = if and [n >= 0,n `tagMember` s, n /= tag (workspace (current s))]
-            then maybe s go (peek s) else s
-    where go w = foldr ($) s [view (tag (workspace (current s))),insertUp w,view n,delete w]
-                           --  ^^ poor man's state monad :-)
+shift n s = if n >= 0 && n `tagMember` s && n /= curtag
+              then maybe s go (peek s) else s
+    where go w = view curtag . insertUp w . view n . delete w $ s
+          curtag = tag (workspace (current s))
-- 
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