From 3bb617aba627d391b422ee10c799ac51524a2bdb Mon Sep 17 00:00:00 2001
From: Jed Barber <jjbarber@y7mail.com>
Date: Tue, 29 May 2012 07:31:11 +1000
Subject: Moved Stack datatype to separate file

---
 Stack.hs | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 Stack.hs

diff --git a/Stack.hs b/Stack.hs
new file mode 100644
index 0000000..2b369b7
--- /dev/null
+++ b/Stack.hs
@@ -0,0 +1,39 @@
+module Stack (
+	Stack,
+    empty,
+    at,
+    pop,
+    (<:>)
+    ) where
+
+
+import Data.List
+
+
+data Stack a = Stack [a]
+
+
+instance Show a => Show (Stack a) where
+    show (Stack x)   =   "Stack:\n" ++ intercalate "\n" (map (show) x) ++ "\n\n"
+
+
+infixr 9 <:>
+
+
+empty :: Stack a
+empty = Stack []
+
+
+at :: Stack a -> Int -> Maybe a
+at (Stack list) index =
+    if (index < length list && index >= 0)
+    then Just (list!!index)
+    else Nothing
+
+
+pop :: Int -> Stack a -> Stack a
+pop n (Stack list) = Stack (drop n list)
+
+
+(<:>) :: a -> Stack a -> Stack a
+x <:> (Stack list) = Stack (x : list)
-- 
cgit