通配符用于匹配歧视联盟时的类型 [英] Wildcard for type when matching discriminated unions

问题描述

在下面的现实世界中，我做了一个匹配：

  type Style = Nice |酷|丑陋的
 type Color = Blue |黄色|橙色|灰色|青色
类型ClothingProperties =风格*颜色
 
类型衣服= 
 |服装牛仔服饰性能
 |服装套头衫
 |衬衫服装性能
 
型人物= 
 |人物*衣服
 
让团队= [人物（Jan，牛仔裤（酷炫，蓝色））;人（皮特，衬衫（尼斯，青））;人（哈利，套头衫（丑陋，灰色））] 
 
让matchPerson person = 
与
匹配的人| Person（名字，牛仔裤（Ugly，_）） - > printfn％s穿着丑陋的东西。名称
 |人（名字，套衫（丑陋，_）） - > printfn％s穿着丑陋的东西。名称
 |人（名字，衬衫（丑陋，_）） - > printfn％s穿着丑陋的东西。名称
 | _  - > （）
 
 List.iter（fun x-> matchPerson x）team 
  

<有没有办法创建更有效的匹配，所以我不需要检查每件衣服的情况？就像这样：

 让matchPerson person = 
与
匹配的人| Person（姓名，_（丑陋，_）） - > printfn％s穿着丑陋的东西。名称
 | _  - > （）
  

当然，这是不正确的语法。但是，我怎样才能达到这样的效果呢？ 解决方案

这并不简单，你可以使用反射，但问题在于你的歧视工会需要一些重新设计，因为如果你知道总会有一个ClothingProperties，那么你可以改变它：

  type Style =尼斯|酷|丑陋的
 type Color = Blue |黄色|橙色|灰色|青色
类型ClothingProperties =风格*颜色//或者只是使用元组
 
类型衣物= 
 |牛仔裤
 |套头衫
 |衬衫
 
类型衣服=衣物*衣服物业
类型人物= 
 |字符串的人*衣服
 
让matchPerson人= 
与
匹配的人| Person（姓名，（_，（Ugly，_））） - > printfn％s穿着丑陋的东西。名称
 | _  - > （）
  

相关的问题在这里描述是否有可能将歧视联合标签作为参数传递？

In the following real world example I do a match:

type Style = Nice | Cool | Ugly
type Color = Blue | Yellow | Orange | Grey | Cyan
type ClothingProperties = Style * Color

type Clothes =
| Jeans of ClothingProperties
| Pullover of ClothingProperties
| Shirt of ClothingProperties

type Person =
| Person of string * Clothes

let team = [Person("Jan", Jeans (Cool, Blue)); Person("Pete", Shirt (Nice, Cyan)); Person("Harry", Pullover (Ugly, Grey))]

let matchPerson person=
    match person with
    | Person(name,  Jeans(Ugly,_) ) -> printfn "%s wears ugly stuff." name
    | Person(name,  Pullover(Ugly,_) ) -> printfn "%s wears ugly stuff." name
    | Person(name,  Shirt(Ugly,_) ) -> printfn "%s wears ugly stuff." name
    | _ -> ()

List.iter(fun x->matchPerson x) team

Is there a way to create a more efficient match, so I don't need to check each clothing case? Something like this:

let matchPerson person=
    match person with
    | Person(name,  _ (Ugly,_) ) -> printfn "%s wears ugly stuff." name
    | _ -> ()

Of course, this is not correct syntax. But how can I achieve such an effect?

解决方案

That's not straightforward, you can use reflection, but the problem is that your discriminated union needs some redesign, because if you know there will always be a ClothingProperties then you can change it to this:

type Style = Nice | Cool | Ugly
type Color = Blue | Yellow | Orange | Grey | Cyan
type ClothingProperties = Style * Color // or just use a tuple

type Clothe =
| Jeans 
| Pullover
| Shirt

type Clothes = Clothe *ClothingProperties
type Person =
| Person of string * Clothes

let matchPerson person=
    match person with
    | Person(name,  (_,(Ugly,_)) ) -> printfn "%s wears ugly stuff." name
    | _ -> ()

A related issue is described here Is it possible to pass discriminated union tags as arguments?

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