From 4885bc81e3716841723b585572ff157b4e324198 Mon Sep 17 00:00:00 2001
From: Jed Barber <jjbarber@y7mail.com>
Date: Wed, 26 Mar 2014 16:18:57 +1100
Subject: The interpreter looks suspiciously like a turing machine

---
 Brainfuck/Tape.hs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 Brainfuck/Tape.hs

(limited to 'Brainfuck/Tape.hs')

diff --git a/Brainfuck/Tape.hs b/Brainfuck/Tape.hs
new file mode 100644
index 0000000..8da4352
--- /dev/null
+++ b/Brainfuck/Tape.hs
@@ -0,0 +1,46 @@
+module Brainfuck.Tape (
+    Tape,
+
+    shiftLeft,
+    shiftRight,
+    currentCell,
+    applyToCurrentCell
+    ) where
+
+
+import Control.Monad
+import Data.Maybe
+
+
+
+type Tape a = ([a], Maybe a, [a])
+
+
+
+
+shiftLeft :: Eq a => Tape a -> Tape a
+shiftLeft (x,y,z) = 
+	let x' = if (x /= []) then tail x else x
+	    y' = if (x /= []) then Just (head x) else Nothing
+	    z' = if (isJust y) then (fromJust y):z else z
+	in (x', y', z')
+
+
+
+shiftRight :: Eq a => Tape a -> Tape a
+shiftRight (x,y,z) =
+	let x' = if (isJust y) then (fromJust y):x else x
+	    y' = if (z /= []) then Just (head z) else Nothing
+	    z' = if (z /= []) then tail z else z
+	in (x', y', z')
+
+
+
+currentCell :: Tape a -> Maybe a
+currentCell (_,c,_) = c
+
+
+
+applyToCurrentCell :: (a -> a) -> Tape a -> Tape a
+applyToCurrentCell f (x,y,z) = (x, (liftM f) y, z)
+
-- 
cgit