Haskell Data.Listのリスト操作関数（サンプル付き）

自分用メモ。全関数は網羅していない。

完全なリファレンスはこちら。
http://hackage.haskell.org/package/base-4.9.1.0/docs/Data-List.html

集合操作

>>> [3,1,4,1,5,9] \\ [1,9]
[3,4,1,5]

>>> "dog" `union` "cow"
"dogcw"

>>> [1,2,3,4] `intersect` [2,4,6,8]
[2,4]

部分リスト

>>> inits [1,2,3,4]
[[],[1],[1,2],[1,2,3],[1,2,3,4]]

>>> tails [3, 1, 4, 1, 5, 9]
[[3,1,4,1,5,9],[1,4,1,5,9],[4,1,5,9],[1,5,9],[5,9],[9],[]]

>>> subsequences [3, 1, 4, 1, 5, 9]
[[],[3],[1],[3,1],[4],[3,4],[1,4],[3,1,4],[1],[3,1],[1,1],[3,1,1],[4,1],[3,4,1],[1,4,1],[3,1,4,1],[5],[3,5],[1,5],[3,1,5],[4,5],[3,4,5],[1,4,5],[3,1,4,5],[1,5],[3,1,5],[1,1,5],[3,1,1,5],[4,1,5],[3,4,1,5],[1,4,1,5],[3,1,4,1,5],[9],[3,9],[1,9],[3,1,9],[4,9],[3,4,9],[1,4,9],[3,1,4,9],[1,9],[3,1,9],[1,1,9],[3,1,1,9],[4,1,9],[3,4,1,9],[1,4,1,9],[3,1,4,1,9],[5,9],[3,5,9],[1,5,9],[3,1,5,9],[4,5,9],[3,4,5,9],[1,4,5,9],[3,1,4,5,9],[1,5,9],[3,1,5,9],[1,1,5,9],[3,1,1,5,9],[4,1,5,9],[3,4,1,5,9],[1,4,1,5,9],[3,1,4,1,5,9]]

>>> isSubsequenceOf [3,4,9] [3,1,4,1,5,9]
True

>>> isInfixOf [1,4,1] [3,1,4,1,5,9]
True

>>> isPrefixOf [3,1,4,1] [3,1,4,1,5,9]
True

>>> isSuffixOf [1,5,9] [3,1,4,1,5,9]
True

>>> permutations [1,2,3]
[[1,2,3],[2,1,3],[3,2,1],[2,3,1],[3,1,2],[1,3,2]]

条件を満たす部分リスト

>>> takeWhile (< 3) [1,2,3,4,1,2,3,4]
[1,2]

>>> dropWhile odd [3,1,4,1,5,9]
[4,1,5,9]

>>> dropWhileEnd odd [3,1,4,1,5,9]
[3,1,4]

>>> span odd [3, 1, 4, 1, 5, 9]
([3,1],[4,1,5,9])

>>> break even [3, 1, 4, 1, 5, 9]
([3,1],[4,1,5,9])

グループ化

>>> group [3,3,1,1,1,4,1,5,9]
[[3,3],[1,1,1],[4],[1],[5],[9]]

>>> partition even [1,2,3,4,5]
([2,4],[1,3,5])

挿入

>>> insert 8 [3,1,4,1,5,9]
[3,1,4,1,5,8,9]

削除

>>> stripPrefix "foo" "foobar"
Just "bar"
>>> stripPrefix "foo" "barfoo"
Nothing

結合

>>> intercalate "," ["hoge", "moge", "sage"]
"hoge,moge,sage"

>>> intersperse 5 [1,2,3]
[1,5,2,5,3]

>>> intersperse "," ["hoge", "moge", "sage"]
["hoge",",","moge",",","sage"]

>>> concat $ intersperse "," ["hoge", "moge", "sage"]
"hoge,moge,sage"

Control.Monad.joinもconcatに等しい。

>>> import Control.Monad
>>> join ["hoge", "moge"]
"hogemoge"
>>> join [[1,2], [3,4]]
[1,2,3,4]

繰り返し

>>> take 10 $ iterate (++ "x") ""
["","x","xx","xxx","xxxx","xxxxx","xxxxxx","xxxxxxx","xxxxxxxx","xxxxxxxxx"]

>>> take 10 $ repeat "hoge"
["hoge","hoge","hoge","hoge","hoge","hoge","hoge","hoge","hoge","hoge"]

>>> replicate 3 "hoge"
["hoge","hoge","hoge"]

>>> take 10 $ cycle [3,1,4]
[3,1,4,3,1,4,3,1,4,3]

最大・最小

>>> maximum [3,1,4,1,5,9]
9

>>> maximumBy (\a -> \b -> compare (abs a) (abs b)) [3,1,4,1,5,-9]
-9

>>> minimum [3,1,4,1,5,9]
1

ソート

>>> sortOn abs [-3, 1, -4, 1, -5, 9]
[1,1,-3,-4,-5,9]

行列

>>> transpose [[3,1,4], [1,5,9]]
[[3,1],[1,5],[4,9]]

zipとunzip

>>> zip [3,1,4,1,5,9] [0..]
[(3,0),(1,1),(4,2),(1,3),(5,4),(9,5)]

>>> unzip $ zip [3,1,4,1,5,9] [0..]
([3,1,4,1,5,9],[0,1,2,3,4,5])