bf.hs

module BF (run, Memory, Command) where
import Data.Char

data Memory = Memory [Integer] Integer [Integer]

empty = Memory [0,0..] 0 [0,0..]

type Command = Char

run :: [Commmand] -> (Memory, String)
run cs = exec cs empty ""

exec :: [Command] -> Memory -> String -> (Memory, String)
exec []       m                    s = (m, s)
exec ('+':cs) (Memory xs n ys)     s = run cs (Memory xs (n+1) ys) s
exec ('-':cs) (Memory xs n ys)     s = run cs (Memory xs (n-1) ys) s
exec ('<':cs) (Memory (x:xs) y ys) s = run cs (Memory xs x (y:ys)) s
exec ('>':cs) (Memory xs x (y:ys)) s = run cs (Memory (x:xs) y ys) s
exec ('.':cs) m@(Memory xs y zs)   s = run cs m (s ++ [(chr y)])
exec ('[':cs) m                    s = 

Awesome. No 'while' though, and no 'getc'. :(

I'm going to implement 'while' in this (or at least attempt to)