initial; no loops

Setup.hs

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+#!/usr/bin/env runhaskell
+
+import Distribution.Simple
+main = defaultMain

brainf*ck.cabal

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+Name:                brainfuck
+Version:             0.1.0
+Synopsis:            Brainfuck interpreter and REPL.
+Description:         
+  brainfuck is a Haskell implementation of the programming
+  language Brainfuck(http://www.muppetlabs.com/~breadbox/bf/).
+
+License:             GPL
+License-file:        LICENSE
+Author:              Veit Heller <veitheller.de>
+Maintainer:          Veit Heller <github.com/hellerve>
+Bug-Reports:         http://github.com/hellerve/brainfuck/issues
+Build-Type:          Simple
+Category:            Compilers/Interpreters, Language
+Tested-with:         GHC == 7.8.4, GHC == 7.6.3
+Cabal-Version:       >= 1.2
+Extra-Source-Files:  README.md
+                     LICENSE
+
+Source-Repository head
+    Type:            git
+    Location:        git://github.com/hellerve/brainfuck.git
+
+Executable           brainfuck
+    Build-Depends:   base, containers, haskeline
+    Extensions:      ExistentialQuantification CPP
+    ghc-options:     -Wall -Werror -O2
+    Main-is:         brainf*ck.hs

brainf*ck.hs

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+module Main where
+
+import Data.Char
+import Data.Sequence hiding (null)
+import System.Console.Haskeline
+import System.Environment
+
+name :: String
+name = "brainfuck"
+
+version :: String
+version = "0.1.0"
+
+prompt :: String
+prompt = name ++ "> "
+
+printUsage :: IO ()
+printUsage = do printVersion
+                putStrLn("\nUsage: " ++
+                         "\n\twithout arguments  - runs REPL" ++
+                         "\n\t-h/--help          - display this help message" ++
+                         "\n\nMore information can be found on " ++
+                         "https://github.com/hellerve/unlambda")
+
+printVersion :: IO ()
+printVersion = putStrLn (name ++ " Version " ++ version)
+
+printCommands :: IO ()
+printCommands = putStrLn "Press Ctrl-C to exit interpreter"
+
+program :: String -> Seq Int -> Int -> IO ()
+program "" _ _ = return ()
+program ('>' : l) tape ptr = program l tape (ptr+1)
+program ('<' : l) tape ptr = program l tape (ptr-1)
+program ('+' : l) tape ptr = let newtape = update ptr ((index tape ptr) + 1) tape
+                             in  program l newtape ptr
+program ('-' : l) tape ptr = let newtape = update ptr ((index tape ptr) - 1) tape
+                             in  program l newtape ptr
+program ('.' : l) tape ptr = do putChar $ chr $ index tape ptr
+                                program l tape ptr
+program (',' : l) tape ptr = do x <- getChar
+                                let newtape = update ptr (ord x) tape
+                                program l newtape ptr
+program (x : _) _ _ = putStrLn ("Unknown instruction: " ++ [x])
+
+main :: IO ()
+main = do
+        args <- getArgs
+        if null args
+            then do printVersion
+                    printCommands
+                    putStrLn ""
+                    repl
+            else
+                if(head args ==  "-h") || (head args == "--help")
+                    then printUsage
+                    else exec args
+
+exec :: [String] -> IO ()
+exec _ = undefined
+
+getInput :: IO String
+getInput = runInputT defaultSettings repl_
+    where repl_ = do
+          x <- getInputLine "> "
+          case x of
+            Nothing -> return ""
+            Just i  -> return i
+
+repl :: IO ()
+repl = do input <- getInput
+          case input of
+            ""     -> repl
+            "quit" -> putStrLn "Bye"
+            x      -> do program x (zeroes 30000 empty) 0
+                         putStrLn ""
+                         repl
+    where zeroes :: Int -> Seq Int -> Seq Int
+          zeroes 0 l = l
+          zeroes n l = zeroes (n-1) (l |> 0)