代码之家 › 专栏 › 技术社区 › John Palmer

F尾。头加列表

list f#

-1

John Palmer · 技术社区 · 15 年前

我正在尝试编写一些用于操作多项式的F代码,作为其中的一部分,我希望将列表中的重复元素组合为单个元素,下面是相关代码:

type PolynomialElem(Coeff : double, Power : int) =
  member x.Coeff = Coeff
  member x.Power = Power
let rec removeDuplicates (inlist:list<PolynomialElem>) (outlist:list<PolynomialElem>) =   
    match inlist with
        |head:: tail ->if head.Power = tail.Head.Power then
                            PolynomialElem(head.Coeff + tail.Head.Coeff) :: removeDuplicates tail.Tail
                        else
                            head :: (removeDuplicates(tail))
        |[] -> []

这会产生两组不同的错误:

The head.Coeff + tail.head.Coeff produces a type mismatch saying "type double * int doesn't match type double"

另外,编译器对我连接列表的方式也不满意,说:

This expression was expected to have type PolynomialElem list but here has type PolynomialElem list -> PolynomialElem list

有什么帮助吗?

1 回复 | 直到 10 年前

1

Brian 15 年前

以下是编译的代码:

type PolynomialElem(Coeff : double, Power : int) =
  member x.Coeff = Coeff
  member x.Power = Power
let rec removeDuplicates (inlist:list<PolynomialElem>)  =   
    match inlist with
        |head:: tail ->if head.Power = tail.Head.Power then
                            PolynomialElem(head.Coeff + tail.Head.Coeff, head.Power) :: removeDuplicates tail.Tail
                        else
                            head :: (removeDuplicates(tail))
        |[] -> []

你忘了传递给多项式的第二个参数(幂)

您有一些未使用/不需要的“离群值”参数。