Tinker Interpreter v2

import Data.List

type Program = ([String], [String], Int, Int, [Int])

replace :: [a] -> [a] -> Int -> a -> [a]
replace lst infTail index str =
    if index < (length lst)
        then (take index lst) ++ [str] ++ (drop (index + 1) lst)
    else
        replace (lst ++ infTail) infTail index str

getValue :: String -> Int
getValue str = if (head str) == '#' then read (tail str) else 0

firstOutermostBracketAndComplement :: String -> (String, String)
firstOutermostBracketAndComplement str = ((takeWhile ('[' ==) str) ++ (takeWhile (']' /=) (dropWhile ('[' ==) str)) ++ (map (\x -> ']') [1..depth]), (dropWhile (']' ==) (dropWhile (']' /=) str)))
    where depth = length (takeWhile ('[' ==) str)

separateFirstInstruction :: String -> (String, String)
separateFirstInstruction str
    |elem c "io._$>^v" = ([c], tail str)
    |c == '[' = firstOutermostBracketAndComplement str
    |c == '{' = (str, "")
    |elem c "#+-" = ([c] ++ takeWhile (\x -> elem x "0123456789") (tail str), dropWhile (\x -> elem x "0123456789") (tail str))
        where c = head str

splitIntoInstructions' :: String -> [String]
splitIntoInstructions' str
    |str == "" = []
    |otherwise = [inst] ++ (splitIntoInstructions' rest) --map (\x -> "_") [0..]
        where (inst, rest) = separateFirstInstruction str

splitIntoInstructions :: String -> [String]
splitIntoInstructions str = if notElem '{' str then splitIntoInstructions' (str ++ "{_}") else splitIntoInstructions' str

setUpProgram :: [String] -> Program
setUpProgram lst = if start == [] then ((init lst), infiniteTail, 0, 0, []) else ((init lst), infiniteTail, 0, (\(Just x) -> x) (elemIndex (head start) lst), [])
        where start = filter (\x -> (head x) == '*') lst
              infiniteTail = splitIntoInstructions' (tail (init (last lst)))

performStep :: Program -> Program
performStep (source, infiniteTail, value, location, out)
        |s == "_" = (source, infiniteTail, value, location + 1, out)
        |s == "$" = (source, infiniteTail, location, location + 1, out)
        |s == ">" = (source, infiniteTail, value, value, out)
        |s == "^" = (source, infiniteTail, getValue (source !! value), location + 1, out)
        |head s == '+' = (source, infiniteTail, value + (read (tail s)), location + 1, out)
        |head s == '-' = (source, infiniteTail, value - (read (tail s)), location + 1, out)
        |head s == '#' = (source, infiniteTail, read (tail s), location + 1, out)
        |head s == '[' = (replace source infiniteTail value (init (tail s)), infiniteTail, value, location + 1, out)
        |s == "v" = (replace source infiniteTail location ("#" ++ (show value)), infiniteTail, value, location + 1, out)
        |s == "o" = (source, infiniteTail, value, location + 1, out ++ [value])
                where s = source !! location

runProgram :: Program -> [Int] -> [Int]
runProgram (source, infiniteTail, value, location, out) inp
        |location >= (length source) - 1 = runProgram (source ++ infiniteTail, infiniteTail, value, location, out) inp
        |source !! location == "." = out
        |source !! location == "i" = runProgram (source, infiniteTail, head inp, location + 1, out) (tail inp)
        |otherwise = runProgram (performStep (source, infiniteTail, value, location, out)) inp
--                where s = source !! location

executeProgram :: String -> [Int] -> [Int]
executeProgram src inp = runProgram (setUpProgram (splitIntoInstructions src)) inp

executeProgramNoInput :: String -> [Int]
executeProgramNoInput src = executeProgram src []