Meaning of contravariance | Babel Free

Definitions

1. The reversal of the order of data types acted upon by an operator.
   countable, uncountable
2. A functor which reverses composition.
   countable, uncountable
3. Of vectors, the property of scaling inversely with a change of basis, as opposed to covariance.
   countable, uncountable

Equivalents

Examples

“I get why with covariance I can return a Dog (a Dog is a Mammal), but why does contravariance work the other way? Shouldn't it accept a derived type when it expects a base type? Contravariance is consistent with Postel's Law: […]”

CEFR level