F#连接字符串选项列表

Question

如何连接字符串选项列表？

let m = [ ""; "12"; "a"; "b"] 
// I can join these with 
m |> List.toSeq |> String.concat "\n" 

// now I got a list of string option list 
let l = [Some ""; None; Some "a"; Some "b"] 
l |> List.toSeq |> ????

Answer 1

首先使用List.choose "提取"列表的某些值:

l |> List.choose id |> String.concat "\n"

请注意,您不需要,List.toSeq因为seq是IEnumerable的别名,并且列表已经实现了它.