What is covariance and contravariance in generic?
What is covariance and contravariance in generic?
Covariance and contravariance are terms that refer to the ability to use a more derived type (more specific) or a less derived type (less specific) than originally specified. Generic type parameters support covariance and contravariance to provide greater flexibility in assigning and using generic types.
What is covariance and contravariance in Java?
Covariance can be translated as “different in the same direction,” or with-different, whereas contravariance means “different in the opposite direction,” or against-different. Covariant and contravariant types are not the same, but there is a correlation between them.
Why is covariance and contravariance important?
This is mainly useful when using already defined standard interfaces. Covariance means that you can use IEnumerable in place where IEnumerable is expected. Contravariance allows you to pass IComparable as an argument of a method taking IComparable . So far, so good.
What is covariance and contravariance in C# and how is it used?
Contravariance allows you to utilize a less derived type than originally specified, and covariance lets you use a more derived type. In a sense, the reason they were brought to the C# language is so you can extend arrays, delegate types and generic types with polymorphistic features.
Which are the types of generic variance?
Various types of variance are: Invariant, Covariant and Contravariant.
What is the difference between covariant and contravariant vectors?
In differential geometry, the components of a vector relative to a basis of the tangent bundle are covariant if they change with the same linear transformation as a change of basis. They are contravariant if they change by the inverse transformation.
What is the meaning of covariance and invariance?
Invariance: refers to the property of objects being left unchanged by symmetry operations. Covariance: refers to equations whose form is preserved by a change of coordinate system.
Why is contravariance useful?
The items in the basket may be of any concrete kind derived from StockItem . An example use of contravariance is when you want to apply some action to an item or collection of items via a base class type, even though you have a derived type.
What is covariance in C sharp?
Covariance in C# Covariance enables you to pass a derived type where a base type is expected. Co-variance is like variance of the same kind. The base class and other derived classes are considered to be the same kind of class that adds extra functionalities to the base type.
What is covariance in OOP?
Covariance means that a method can return a type that is derived from the delegate’s return type. Contra-variance means that a method can take a parameter that is a base of the delegate’s parameter type.