<!doctype html> <html> <head> <title>CodeMirror: Haskell mode</title> <link rel="stylesheet" href="../../lib/codemirror.css"> <script src="../../lib/codemirror.js"></script> <script src="haskell.js"></script> <link rel="stylesheet" href="../../theme/elegant.css"> <style type="text/css">.CodeMirror {border-top: 1px solid black; border-bottom: 1px solid black;}</style> <link rel="stylesheet" href="../../doc/docs.css"> </head> <body> <h1>CodeMirror: Haskell mode</h1> <form><textarea id="code" name="code"> module UniquePerms ( uniquePerms ) where -- | Find all unique permutations of a list where there might be duplicates. uniquePerms :: (Eq a) => [a] -> [[a]] uniquePerms = permBag . makeBag -- | An unordered collection where duplicate values are allowed, -- but represented with a single value and a count. type Bag a = [(a, Int)] makeBag :: (Eq a) => [a] -> Bag a makeBag [] = [] makeBag (a:as) = mix a $ makeBag as where mix a [] = [(a,1)] mix a (bn@(b,n):bs) | a == b = (b,n+1):bs | otherwise = bn : mix a bs permBag :: Bag a -> [[a]] permBag [] = [[]] permBag bs = concatMap (\(f,cs) -> map (f:) $ permBag cs) . oneOfEach $ bs where oneOfEach [] = [] oneOfEach (an@(a,n):bs) = let bs' = if n == 1 then bs else (a,n-1):bs in (a,bs') : mapSnd (an:) (oneOfEach bs) apSnd f (a,b) = (a, f b) mapSnd = map . apSnd </textarea></form> <script> var editor = CodeMirror.fromTextArea(document.getElementById("code"), { lineNumbers: true, matchBrackets: true, theme: "elegant" }); </script> <p><strong>MIME types defined:</strong> <code>text/x-haskell</code>.</p> </body> </html>