|
0
|
1 <!doctype html>
|
|
|
2
|
|
|
3 <title>CodeMirror: Haskell mode</title>
|
|
|
4 <meta charset="utf-8"/>
|
|
|
5 <link rel=stylesheet href="../../doc/docs.css">
|
|
|
6
|
|
|
7 <link rel="stylesheet" href="../../lib/codemirror.css">
|
|
|
8 <link rel="stylesheet" href="../../theme/elegant.css">
|
|
|
9 <script src="../../lib/codemirror.js"></script>
|
|
|
10 <script src="../../addon/edit/matchbrackets.js"></script>
|
|
|
11 <script src="haskell.js"></script>
|
|
|
12 <style>.CodeMirror {border-top: 1px solid black; border-bottom: 1px solid black;}</style>
|
|
|
13 <div id=nav>
|
|
|
14 <a href="https://codemirror.net/5"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png" alt=""></a>
|
|
|
15
|
|
|
16 <ul>
|
|
|
17 <li><a href="../../index.html">Home</a>
|
|
|
18 <li><a href="../../doc/manual.html">Manual</a>
|
|
|
19 <li><a href="https://github.com/codemirror/codemirror5">Code</a>
|
|
|
20 </ul>
|
|
|
21 <ul>
|
|
|
22 <li><a href="../index.html">Language modes</a>
|
|
|
23 <li><a class=active href="#">Haskell</a>
|
|
|
24 </ul>
|
|
|
25 </div>
|
|
|
26
|
|
|
27 <article>
|
|
|
28 <h2>Haskell mode</h2>
|
|
|
29 <form><textarea id="code" name="code">
|
|
|
30 module UniquePerms (
|
|
|
31 uniquePerms
|
|
|
32 )
|
|
|
33 where
|
|
|
34
|
|
|
35 -- | Find all unique permutations of a list where there might be duplicates.
|
|
|
36 uniquePerms :: (Eq a) => [a] -> [[a]]
|
|
|
37 uniquePerms = permBag . makeBag
|
|
|
38
|
|
|
39 -- | An unordered collection where duplicate values are allowed,
|
|
|
40 -- but represented with a single value and a count.
|
|
|
41 type Bag a = [(a, Int)]
|
|
|
42
|
|
|
43 makeBag :: (Eq a) => [a] -> Bag a
|
|
|
44 makeBag [] = []
|
|
|
45 makeBag (a:as) = mix a $ makeBag as
|
|
|
46 where
|
|
|
47 mix a [] = [(a,1)]
|
|
|
48 mix a (bn@(b,n):bs) | a == b = (b,n+1):bs
|
|
|
49 | otherwise = bn : mix a bs
|
|
|
50
|
|
|
51 permBag :: Bag a -> [[a]]
|
|
|
52 permBag [] = [[]]
|
|
|
53 permBag bs = concatMap (\(f,cs) -> map (f:) $ permBag cs) . oneOfEach $ bs
|
|
|
54 where
|
|
|
55 oneOfEach [] = []
|
|
|
56 oneOfEach (an@(a,n):bs) =
|
|
|
57 let bs' = if n == 1 then bs else (a,n-1):bs
|
|
|
58 in (a,bs') : mapSnd (an:) (oneOfEach bs)
|
|
|
59
|
|
|
60 apSnd f (a,b) = (a, f b)
|
|
|
61 mapSnd = map . apSnd
|
|
|
62 </textarea></form>
|
|
|
63
|
|
|
64 <script>
|
|
|
65 var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
|
|
|
66 lineNumbers: true,
|
|
|
67 matchBrackets: true,
|
|
|
68 theme: "elegant"
|
|
|
69 });
|
|
|
70 </script>
|
|
|
71
|
|
|
72 <p><strong>MIME types defined:</strong> <code>text/x-haskell</code>.</p>
|
|
|
73 </article>
|
