contravariance

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Contravariance and val

How and why does \'val\' and \'case\' affect the type system? (Especially the variance) Welcome to Scala version 2.8.1.final (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_22).[详细]

2023-02-13 14:34 分类：问答
Implementing Co and Contra variance generic interface & its practical uses

I am trying to understand the possible use of using a variant generic interface(using both co and contra variant). Can someone please explain? I understood co and contra variance examples for interfac[详细]

2023-02-13 04:19 分类：问答
Casting List<T> - covariance/contravariance problem

Given the following types: public interface IMyClass { } public class MyClass : IMyClass { } I wonder how can I convert a List<MyClass> to a List<IMyClass>? I am not completely clear on[详细]

2023-02-09 09:36 分类：问答
How to implement template class covariance in C++?

Is it possible to implement a class template in such a way that one object could be casted to another if their template arguments are related? Here is an exaple to show the idea (of course it will not[详细]

2023-02-09 06:23 分类：问答
Can I implement an interface that contains a property that is of child type to what is required by the interface?

I am receiving the following error: ClassName.PropertyName cannot implementIClassType.PropertyName because it does not have the matching return type of IBasePropertyType[详细]

2023-02-08 03:48 分类：问答
Simple examples of co and contravariance

Could someone provide me simple C# examples of convariance, contravariance, invariance and contra-invariance (if such thing exi开发者_运维问答sts).[详细]

2023-02-03 16:22 分类：问答
Covariance and Contravariance on the same type argument

The C# spec states that an argument type cannot be both covariant and contravariant at the same time.[详细]

2023-02-01 17:13 分类：问答
Why doesn't delegate contravariance work with value types?

This snippet is not compiled in LINQPad. void Main() { (new[]{0,1,2,3}).Where(IsNull).Dump(); } static bool IsNull(object arg) { return arg == null; }[详细]

2023-01-23 17:34 分类：问答
General 'map' function for Scala tuples?

I would like to map the elements of a Scala tuple (or triple, ...) using a single function returning type R.The result should be a tuple (or triple, ...) with elements of type R.[详细]

2023-01-21 19:33 分类：问答
C# 4.0 Generics and ASP.net MVC

It appears that in C# 4.0, variance specifiers are only applicable to interface types. So let\'s say I have ViewModel / EditModel classes and a simple hierarc开发者_运维技巧hy of models.[详细]

2023-01-19 17:15 分类：问答