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Contravariance in the real world

Vitor Nunes on August 12, 2018

Contravariance hurts the brain! The definition is straightforward, but applying it to the real world doesn’t make much sense. How come Container[Wa...

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Bob van Hoove • Aug 13 '18

Thanks for bringing this up, it never quite stuck with me.

Here's a C# example using the 'accepts' phrasing:

// Covariant:
//
//         generic    (accepts)   specific
//
IEnumerable<object> objects = new string[] { "a", "b", "c" }; 


// Contravariant:
//
//    specific      (accepts)       generic
//
Action<string> printIt = new Action<object>(o => Console.WriteLine(o));

Pretty much copied from MSDN : Covariance and Contravariance FAQ