takeWhile
(a -> Bool) -> [a] -> [a]
https://hackage.haskell.org/package/base-4.18.0.0/docs/Prelude.html#v:takeWhile
述語
p
を満たす最長の先頭側のリストを返す
code:hs
>> takeWhile (< 3)
1,2,3,4,1,2,3,4
1,2
>> takeWhile (< 9)
1,2,3
1,2,3
>> takeWhile (< 0)
1,2,3
[]
dropWhile
逆に、後ろ側
(<3)
と
[1,2,3,4,5,6,7]
のとき
code:_
↓ ↓ takeWhile
1,2,3,4,5,6,7
↑ ↑ ↑ ↑ ↑ dropWhile