如何在不中断对其他类型的支持的情况下适当地重载全局(+)和(*) [英] How to properly overload global (+) and (*) without breaking support for other types

问题描述

我已经导入了向量数学库，并希望添加自己的(*)和(+)运算符，同时保留现有的基本int和float运算符.

I have imported a vector math library, and would like to add my own (*) and (+) operators while preserving the existing operators for basic int and float.

我尝试了以下操作:

let inline (*) (x : float) (y : Vector) = y.Multiply(x)
let inline (*) (x : Vector) (y : float) = x.Multiply(y)
let inline (+) (x : Vector) (y : Vector) = x.Add(y)

有两个问题:

1. 似乎删除了int + int和int * int以及
2. 第二行(旨在实现可交换性)未编译，因为它是重复定义".

1. It seems to remove int + int and int * int, and
2. The 2nd line (which is intended to complete commutativity) does not compile because it is a "duplicate definition".

如何在导入的Vector类型上定义一些可交换运算符，同时又不丢失int和float上的这些运算符?

How can I go about defining some commutative operators on my imported Vector type while also not losing these operations on ints and floats?

(我希望能够使用*和+在其他地方编写通用代码，而不必指定float/Vector/int类型约束).

(I want to be able to write generic code elsewhere using * and +, without having to specify float/Vector/int type constraints).

推荐答案

如果您能够修改库的源代码，则通过类型扩展添加一些重载会更简单:

If you are able to modify source code of the library, it's simpler to add a few overloads via type extensions:

type Vector with
    static member (*) (x : Vector) (y : float) = x.Multiply(y)
    static member (+) (x : Vector) (y : Vector) = x.Add(y)

但是，如果第一个操作数具有基本类型(例如您的第一个示例)，则重载解析不再起作用.

However, if the first operand has a primitive type (e.g your first example), overloading resolution doesn't work any more.

无论如何，您可以利用成员重载并将约束传播到内联函数:

At any rate, you can exploit member overloading and propagate constraints to an inline function:

type VectorOverloadsMult =
    | VectorOverloadsMult
    static member (?<-) (VectorOverloadsMult, x: float, y: Vector) = y.Multiply(x)
    static member (?<-) (VectorOverloadsMult, x: Vector, y: float) = x.Multiply(y)     
    static member inline (?<-) (VectorOverloadsMult, x, y) = x * y

let inline (*) x y = (?<-) VectorOverloadsMult x y

这适用于使用(*)的现有类型，因为我们将它们保留在最后一个静态成员中.您可以对(+)运算符执行相同的操作.

This works for existing types with (*) since we preserve them in the last static member. You can do the same for (+) operator.

let v: Vector = ... // Declare a Vector value
let a = 2.0 * v
let b = v * 2.0
let c = 2 * 3
let d = 2.0 * 3.0

即使您无法修改Vector类型，该技术也可以使用.

This technique works even when you cannot modify the Vector type.

这篇关于如何在不中断对其他类型的支持的情况下适当地重载全局(+)和(*)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！