Execute Brain****/Haskell: Difference between revisions
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(unsafePerformIO sounds scary) |
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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). |
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). |
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In functional style, ''run'' interprets a Brainfuck program as a function from an Integer list (inputs) to an Integer list (outputs). |
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''. |
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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. |
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. |
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import System.IO.Unsafe |
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moveLeft (x:l,r) = (l,x:r) |
moveLeft (x:l,r) = (l,x:r) |
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moveRight (l,x:r) = (x:l,r) |
moveRight (l,x:r) = (x:l,r) |
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dialog :: String -> IO () |
dialog :: String -> IO () |
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dialog s = mapM_ print |
dialog s = mapM_ print . run s . map read . lines =<< getContents |
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Example session: |
Example session: |
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Revision as of 10:26, 21 December 2008
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.
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 (- 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