Covariance and contravariance (computer science): Difference between revisions

Revision as of 09:45, 1 November 2021

Revision as of 03:44, 3 November 2021

Line 13:

== Formal definition ==

{{More citations needed section|date=November 2021}}

Within the [[type system]] of a [[programming language]], a typing rule or a type constructor is:

* ''covariant'' if it preserves the [[subtyping|ordering of types (≤)]], which orders types from more specific to more generic: If <code>A ≤ B</code>, then <code>I<nowiki><A> ≤ I<B></nowiki></code>;