该表达式预计具有类型单位

Question

我有以下代码.在这一行

 if min<=0  then     min <- List.nth list i |>ignore

我有2个错误.首先是0它

 This expression was expected to have type
    unit    
but here has type
    int

然后在i它

This expression was expected to have type
    unit    
but here has type
    int

*我也看过这个 并尝试忽略,但它不起作用

let replace touple2=
   let first  (a,_,_,_,_)=a
   let second (_,b,_,_,_)=b
   let third  (_,_,c,_,_)=c
   let forth  (_,_,_,d,_)=d
   let fifth  (_,_,_,_,e)=e
   let sortedlist list= List.sort(list)

   let GetMin list=
        list |> List.rev |> List.head
        let mutable min=list.Head
        let mutable i=1
        for i in list do     
            if min<=0  then     min <- List.nth list i |>ignore

        min 

   let GetMax list=list |> List.rev |> List.head

   let A=first  touple2
   let B=second touple2
   let C=third  touple2
   let D=forth  touple2
   let E=fifth  touple2
   let mylist=[A;B;C;D;E]
   let L=sortedlist mylist

   let m1=GetMax L
   printfn "%d"  m1

let touple3= 14,6,18,76,76
replace touple3

Answer 1

您不需要ignore- 如果您正在使用赋值,它将返回unit,因此您没有任何必须忽略的返回值:

if min <= 0 then min <- List.nth list I

也就是说,这不是很实用的方法.因此,查看一些基本的F#书或观看一些演讲可能会帮助您开始使用更多F#风格的语言.