Haskell相交(List)

Question

我试图得到两个列表相交的"对立面":如:

let all  = [1..5]
let mask = [2,3]
let res  = ???
-- let res = all `intersect` mask <-- reverse/opposite ?
-- I want to get [1,4,5] ?

Answer 1

你正在寻找集合差异,这是Data.List的\\运算符:

Prelude> import Data.List ((\\))
Prelude Data.List> let all  = [1..5]
Prelude Data.List> let mask = [2,3]
Prelude Data.List> all \\ mask
[1,4,5]