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0 pointsevincarofautumn12y ago0 comments

T is covariant (positive) if A ≤: B ⇒ T<A> ≤: T<B>. T is contravariant (negative) if A ≤: B ⇒ T<B> ≤: T<A> (i.e., the other way around). Pretty simple stuff.

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pkolaczk12y ago

It is easy to remember if you think of it:

+ (covariant): the type can be cast to some broader (more general) type

- (contravariant): the type can be cast to some narrower (more concrete) type

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