F#类型选项问题

Question

我有以下代码:

let rec sums1 n = function
            | (a,b,x:int array,s,k) when (s<n&&b=x.Length-1) -> []//None
            | (a,b,x:int array,s,k) when (a=b&&((x.Length-1)=b))->[]// None 
            | (a,b,x,s,k) when (s=n) -> (Array.toList(Array.sub x a k)) 
            | (a,b,x,s,k) when (s<n) -> sums1 n (a,b+1,x,s+x.[b+1],k+1)
            | (a,b,x,s,k) when (s>n) -> sums1 n (a+1,b,x,s-x.[a],k-1)    
            | (a,b,c,d,e) -> []//None

let neco n s =match (sums1 n (0,-1,s,0,0)) with
        | [] ->None
        | x ->Some x
let ssum n xs:list<int> = neco n (List.toArray xs)

如何编译器不允许我从类型选项<list <int >>的ssum值返回.我将返回此类型,而不是其他类型.有人知道吗？十分感谢.

Answer 1

我想你只是错过了一些问题:

let ssum n (xs:list<int>) = neco n (List.toArray xs) 
           ^            ^

没有它们,您将描述返回类型ssum,而不是参数类型xs.