f# - 如何在F#中为各种角色定义int、float等类型的同义词？

Question

我想在各种角色中使用像“int”这样的简单类型，编译器会阻止我无意中混淆不同角色的变量。使用度量单位似乎提供了一种(简单的)解决方法。

[<Measure>]
type xcoordinate
[<Measure>]
type ycoordinate

type xci = int<xcoordinate>
type yci = int<ycoordinate>

let fnc (x:xci) (y:yci) = ...

// Now 'fnc' can be called only with a proper x-y coordinate pair.
// Is there any way to use the type synonyms to coerce an 'int' to  
// int<xcoordinate> instead of writing 2<xcoordinate>, for instance? 

Answer 1

“明显”的想法，至少我有，是使用单一案例区分联合。

type XCoordinate = XCoordinate of int
type YCoordinate = YCoordinate of int

let fnc (x:XCoordinate) (y:YCoordinate) = ()

let x = 1 
let y = 1

let xc = XCoordinate(x)
let yc = YCoordinate(y)


let resNoCompile = fnc x y //wont compile

let res = fnc xc yc //works as expected

您仍然无法在同一角色中混合使用整数和 float 。我想。