f# - 简单解析命令行参数

Question

我想使用以下代码来限制只有一个参数。但是，我在 first :: NIL 收到以下错误？

Error   1   This expression was expected to have type    string []    but here has type    'a list 

[<EntryPoint>]
let main argv = 

    match argv with 
    | first :: NIL -> 
         .... do something with first
    | _ -> failwith "Must have only one argument."

Answer 1

命令行参数作为数组传递，而不是列表。

如果您只期望一个参数，请执行以下操作:

match argv with 
| [|first|] -> 
     // .... do something with first
| _ -> failwith "Must have only one argument."