.Net 支持柯里化泛型吗？

发布于 2024-10-31 13:22:54 字数 374 浏览 0 评论 0原文

假设我们有一个嵌套泛型类：

public class A<T> {
    public class B<U> { }
}

这里，typeof(A.B<>)本质上是一个具有两个参数的泛型类，其中仅绑定第一个参数。

如果我有一个带有两个参数的类，

public class AB<T, U> { }

有没有办法引用“AB，其中 T=int 和 U 保持打开状态”？如果不是，这是 C# 限制还是 CLR 限制？

原文

Suppose we have a nested generic class:

public class A<T> {
    public class B<U> { }
}

Here, typeof(A<int>.B<>) is in essence a generic class with two parameters where only the first is bound.

If I have a single class with two parameters

public class AB<T, U> { }

Is there a way to refer to "AB with T=int and U staying open"? If not, is this a C# limitation, or a CLR limitation?

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草莓酥 2024-11-07 13:22:54

显然这不能在 C# 中完成，您必须指定两个类型参数，或者都不指定。

而且 CLR 似乎也不支持， A.B<> 和 A.B<> 指的是相同类型：

Type t1 = typeof(A<int>).GetNestedType("B`1");
Type t2 = typeof(A<string>).GetNestedType("B`1");
// t1.Equals(t2) is true

两种类型的封闭类型是 A<> （开放泛型类型）

编辑：进一步测试表明 typeof(A.B) 实际上是 arity 2 的泛型类型，不是 arity 1 的嵌套泛型类型... typeof(A.B).GetGenericArguments() 返回一个带有 typeof(int) 和 typeof(string) 的数组。因此 typeof(A.B<>) 实际上相当于 (AB)，这是不支持的（泛型类型不能部分关闭）

Apparently it can't be done in C#, you have to specify either both type parameters, or none.

And it doesn't seem to be supported by the CLR either, A<int>.B<> and A<string>.B<> refer to the same type:

Type t1 = typeof(A<int>).GetNestedType("B`1");
Type t2 = typeof(A<string>).GetNestedType("B`1");
// t1.Equals(t2) is true

The enclosing type of both types is A<> (open generic type)

EDIT: further testing shows that typeof(A<int>.B<string>) is actually a generic type of arity 2, not a nested generic type of arity 1... typeof(A<int>.B<string>).GetGenericArguments() returns an array with typeof(int) and typeof(string). So typeof(A<int>.B<>) would actually be equivalent to (A.B)<int, >, which isn't supported (a generic type can't be partially closed)

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忆依然 2024-11-07 13:22:54

这是你的想法吗？

   class AB<T, U>
   {
      protected T t;
      U u;
   }

   class C<U> : AB<int, U>
   {
      public void Foo()
      {
         t = 5;
      }
   }

Is this what you have in mind?

   class AB<T, U>
   {
      protected T t;
      U u;
   }

   class C<U> : AB<int, U>
   {
      public void Foo()
      {
         t = 5;
      }
   }

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给妤﹃绝世温柔 2024-11-07 13:22:54

您可以使用 Func;泛型将多个参数作为返回类型的单个函数传递。柯里化了很多，将许多参数作为单个参数传递。

 [Fact]
    public async Task TestCurried()
    {
        Func<int, Func<int, int>> curried = x => y => x + y;
        int sum = curried(1)(3);
        Assert.Equal(sum.ToString(), "4");
    }
see
https://blog.tchatzigiannakis.com/generics-as-super-functions/

you can use the Func<int,int> generic to pass multiple parameters as a single function returning an type. Curried many to pass many arguments as a single parameter.

 [Fact]
    public async Task TestCurried()
    {
        Func<int, Func<int, int>> curried = x => y => x + y;
        int sum = curried(1)(3);
        Assert.Equal(sum.ToString(), "4");
    }
see
https://blog.tchatzigiannakis.com/generics-as-super-functions/

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