Execute Brain****/Haskell is an implementation of Brainf***.
Other implementations of Brainf***.
Execute Brain****/Haskell is part of RCBF. You may find other members of RCBF at Category:RCBF.
Quick implementation of a Brainfuck interpreter in Haskell.
Pairs of lists are used to implement both the two-side infinite band of cells, and the program storage. This means that it can also work on infinite Brainfuck programs (which could be generated lazily).
In functional style, run interprets a Brainfuck program as a function from an Integer list (inputs) to an Integer list (outputs). This can be easily turned into a real dialog with a user via stdin and stdout.
A more efficient implementation could for example only admit well-bracketed brainfuck programs, and parse bracket blocks first, to replace the matchLeft and matchRight which need linear time.
module BF where(This version compiles with GHC and will run if loaded into ghci using ':load BF')
moveLeft (x:l,r) = (l,x:r)
moveRight (l,x:r) = (x:l,r)
matchLeft d@('[':_,_) = d
matchLeft d@(']':_,_) = matchLeft $ moveLeft $ matchLeft $ moveLeft $ d
matchLeft d = matchLeft $ moveLeft $ d
matchRight d@(_,']':_) = moveRight $ d
matchRight d@(_,'[':_) = matchRight $ matchRight $ moveRight $ d
matchRight d = matchRight $ moveRight $ d
pad ([],[]) = ([0],[0])
pad ([],r) = ([0],r)
pad (l,[]) = (l,[0])
pad d = d
modify f (l,x:r) = (l,(f x):r)
exec :: (String, String) -> ([Integer], [Integer]) -> [Integer] -> [Integer]
exec (_,[]) _ _ = []
exec p@(_,'>':_) d cs = exec (moveRight p) (pad $ moveRight $ d) cs
exec p@(_,'<':_) d cs = exec (moveRight p) (pad $ moveLeft $ d) cs
exec p@(_,'+':_) d cs = exec (moveRight p) (modify (+ 1) d) cs
exec p@(_,'-':_) d cs = exec (moveRight p) (modify (subtract 1) d) cs
exec p@(_,',':_) d (c:cs) = exec (moveRight p) (modify (const c) d) cs
exec p@(_,'.':_) d@(_,x:_) cs = x : exec (moveRight p) d cs
exec p@(_,'[':_) d@(_,0:_) cs = exec (matchRight $ moveRight $ p) d cs
exec p@(_,'[':_) d cs = exec (moveRight p) d cs
exec p@(_,']':_) d@(_,0:_) cs = exec (moveRight p) d cs
exec p@(_,']':_) d cs = exec (matchLeft $ moveLeft $ p) d cs
run :: String -> [Integer] -> [Integer]
run s = exec ([],s) ([0],[0])
dialog :: String -> IO ()
dialog s = mapM_ print . run s . map read . lines =<< getContents
Example session:
: *Main> dialog ",[>+<-].>." : ''5'' : 0 : 5
