Endevir
/
git-server


			
				
					
						
						
							12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273
							<!doctype html>

<title>CodeMirror: Haskell mode</title>
<meta charset="utf-8"/>
<link rel=stylesheet href="../../doc/docs.css">

<link rel="stylesheet" href="../../lib/codemirror.css">
<link rel="stylesheet" href="../../theme/elegant.css">
<script src="../../lib/codemirror.js"></script>
<script src="../../addon/edit/matchbrackets.js"></script>
<script src="haskell.js"></script>
<style type="text/css">.CodeMirror {border-top: 1px solid black; border-bottom: 1px solid black;}</style>
<div id=nav>
  <a href="http://codemirror.net"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png"></a>

  <ul>
    <li><a href="../../index.html">Home</a>
    <li><a href="../../doc/manual.html">Manual</a>
    <li><a href="https://github.com/codemirror/codemirror">Code</a>
  </ul>
  <ul>
    <li><a href="../index.html">Language modes</a>
    <li><a class=active href="#">Haskell</a>
  </ul>
</div>

<article>
<h2>Haskell mode</h2>
<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>
  </article>