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Search found 42 results on 2 pages for 'contravariance'.

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• Understanding Covariant and Contravariant interfaces in C#

  - by SLC

  I've come across these in a textbook I am reading on C#, but I am having difficulty understanding them, probably due to lack of context. Is there a good concise explanation of what they are and what they are useful for out there? Edit for clarification: Covariant interface: interface IBibble<out T> . . Contravariant interface: …

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• Why can I not convert from List<IScreen> to List<IRenderable> even when IScreen implements IRenderab

  - by Blub

  Pretty self explanatory question, glad for any answer. For me it doesn't make sense. I don't care about losing information. I just want to concatenate all my lists that inherit IRenderable somehow into a single list and then call IRenderable methods on it. I have a feeling that this is some basic rule of programming I forgot...

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• Can I have a type that's both, covariant and contravariant, i.e. fully fungible/changeable with sub

  - by Water Cooler v2

  Just a stupid question. I could try it out in 2 minutes, really. It's just that I have 1 GB RAM and have already got 2 instances of VS 2010 open on my desktop, with an instance of VS 2005, too. Opening another instance of VS 2010 would be an over kill. Can I have a type (for now forgetting its semantics) that can be covariant as well as…

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• How is covariance cooler than polymorphism...and not redundant?

  - by P.Brian.Mackey

  .NET 4 introduces covariance. I guess it is useful. After all, MS went through all the trouble of adding it to the C# language. But, why is Covariance more useful than good old polymorphism? I wrote this example to understand why I should implement Covariance, but I still don't get it. Please enlighten me. using System; using…

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• ref and out parameters in C# and cannot be marked as variant.

  - by Water Cooler v2

  What does the statement mean? From here ref and out parameters in C# and cannot be marked as variant. 1) Does it mean that the following can not be done. public class SomeClass<R, A>: IVariant<R, A> { public virtual R DoSomething( ref A args ) { return null; } } 2) Or does it mean I cannot…

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• TechDays 2010: What’s New On C# 4.0

  - by Paulo Morgado

  I would like to thank those that attended my session at TechDays 2010 and I hope that I was able to pass the message of what’s new on C#. For those that didn’t attend (or did and want to review it), the presentation can be downloaded from here. Code samples can be downlaoded from here. Here’s a list of resources mentioned on the…

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• Is variance of for generic type parameters in C# 4.0 a step closer for higher kind types?

  - by Aggelos Mpimpoudis

  We know that implementing classes are still invariant, despite the fact that their interfaces are variant. However I am inquiring, is cov/contravariance a step closer to parametric polymorphism or these are two separate concepts?

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• Contravariant Delegates Value Types

  - by ChloeRadshaw

  Can anyone shed light on why contravariance does not work with C# value types? The below does not work private delegate Asset AssetDelegate(int m); internal string DoMe() { AssetDelegate aw = new AssetDelegate(DelegateMethod); aw(32); return "Class1"; } private static House DelegateMethod(object m) { return…

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• What useful minor features of C# 4.0 can you list?

  - by sashaeve

  C# 4.0 has a lot of new major features such as dynamic type, covariance and contravariance, named arguments etc. But C# 4.0 contains new minor (but useful) changes such as TryParse method for TimeSpan, Enum, Guid data types, String.IsNullOrWhiteSpace, System.IO.Stream.CopyTo etc. What other minor and useful features of C#…

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• New features of C# 4.0

  This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for…

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• Functional languages targeting the LLVM

  - by Matthew

  Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics,…

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• Do invariant assertions fit into C# programming?

  - by P.Brian.Mackey

  In the book coders at work, the author asks "How do you use invariants in your code". Please explain what this question means. I saw class invariants on wiki, but the example is in Java and I am not skilled enough in Java to relate this example to C#. .NET 4.0 introduces invariance, covariance, and…

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• CodePlex Daily Summary for Tuesday, November 15, 2011

  CodePlex Daily Summary for Tuesday, November 15, 2011Popular ReleasesTHE NVL Maker: The NVL Maker Ver 3.10: 3.10 ??? ???： ·????????? ·????????? ·???“TJS”?“??”“EXP”?????“???”,???????? ·???“????”???，???????@if~@elsif~@else~@endif????? ·TJS????????? ·???????????else?endif??? ??：…

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• C#/.NET Little Wonders: The Predicate, Comparison, and Converter Generic Delegates

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the last three weeks, we examined…

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• Understanding C# async / await (2) Awaitable / Awaiter Pattern

  - by Dixin

  What is awaitable Part 1 shows that any Task is awaitable. Actually there are other awaitable types. Here is an example: Task<int> task = new Task<int>(() => 0); int result = await task.ConfigureAwait(false); // Returns a…

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• CodePlex Daily Summary for Saturday, November 19, 2011

  CodePlex Daily Summary for Saturday, November 19, 2011Popular ReleasesWPF Converters: WPF Converters V1.2.0.0: support for enumerations, value types, and reference types in the expression converter's equality operators the expression…

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• CodePlex Daily Summary for Friday, November 18, 2011

  CodePlex Daily Summary for Friday, November 18, 2011Popular ReleasesDelta Engine: Delta Engine Beta Preview v0.9.1: v0.9.1 beta release with lots of refactoring, fixes, new samples and support for iOS, Android and WP7 (you need a…

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