リストを前後に2分割

code:haskell

{- $setup

-}

ここでは、前後2分割の列挙する

code:haskell

{- |

>> splits xs

>> all ((xs ==) . uncurry (++)) (splits xs)

True

-}

splits xs = zip (inits xs) (tails xs)

空リストを含まない分割の列挙

code:haskell

{- |

>> splitsNE xs

>> all ((sample ==) . uncurry (++)) (splitsNE sample)

True

-}

splitsNE = \ case

[] -> []

x:xs -> zipWith3 (const (,)) xs ((x:) <$> inits xs) (tails xs)