Contravariance is a complex type theory concept that describes how type parameters behave in the opposite way of what you might expect. It's commonly used in functional programming languages like Haskell and Scala, but can also pop up in more mainstream languages like Java and C# to make overly abstract code bases extra confusing to new developers.

How to use it in a sentence

Did you see that PR from the new guy that used contravariance in the generic type definition? I think he's just trying to look smart since it doesn't even make sense in that context.

I was debugging Karen's code for 3 hours before I realized the bug was due to contravariance in the legacy framework we're forced to use. Just another day in the life of a 10X engineer cleaning up everyone else's messes!

If you actually want to learn more...

• Contravariance is a key concept in understanding how types behave in functional programming. Learn more about it and other advanced type system features in this in-depth guide to Scala's type system.

• For a more beginner-friendly introduction to contravariance and its related concepts, check out this blog post that explains covariance and contravariance using simple examples in Java.

• If you really want to geek out on type theory, this academic paper dives deep into covariance and contravariance from a mathematical perspective. Perfect for some light weekend reading!

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