invariance

Variance has to do with how a generic type F<T> varies with respect to its type parameter T. If you know that T extends U, then variance will tell you whether you can conclude that F<T> extends F<U>, conclude that F<U> extends F<T>, or neither, or both. Covariance means that F<T> and T co–vary. That … Read more

Variance has to do with how a generic type F<T> varies with respect to its type parameter T. If you know that T extends U, then variance will tell you whether you can conclude that F<T> extends F<U>, conclude that F<U> extends F<T>, or neither, or both. Covariance means that F<T> and T co–vary. That … Read more