如何在 F# 中使用中缀运算符定义 class 布尔函数？

Question

也许它已经在 F# 中实现了？

基本上我想用中缀运算符定义一个 class 通用过滤器函数，所以看起来像

type Filter<'T> = ('T -> bool) with 
     static member (|*) (f:Filter<'T>) (g:Filter<'T>) = (fun x -> (f x) || 
     (g x)) // OR operator

但这似乎不是正确的语法

Stopped due to error System.Exception: Operation could not be completed due to earlier error Type abbreviations cannot have augmentations at 2,5 Type abbreviations cannot have members at 3,19

谢谢

Answer 1

你定义的是type abbreviation, which, as the errors will indicate, can neither have augmentations nor members. You could fix that by using a single case discriminated union:

type Filter<'T> = Filter of ('T -> bool) with 
     static member (|* ) (Filter f, Filter g) =
        Filter(fun x -> f x || g x) // OR operator

当然，您现在需要在布尔运算之前解包谓词函数，然后再包装组合函数。一个简单的测试...

let odd x = x % 2 <> 0
let big x = x > 10
let (Filter f) = Filter odd |* Filter big in [8..12] |> List.filter f
// val it : int list = [9; 11; 12]

如何在 F# 中使用中缀运算符定义 class 布尔函数？

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