SUBTYPING Meaning and
Definition
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Subtyping is a concept in type theory that deals with the relationship between different types within a type system. It refers to the relationship where a type can be considered a subtype of another type, if it has all the behaviors and capabilities of the supertype, and possibly some more specific behaviors.
In subtyping, a subtype is said to inherit all the characteristics of its supertype, while potentially adding new features or functions that are specific to the subtype. This inheritance allows for polymorphism, where a value of the subtype can be used in any context that expects the supertype.
Subtyping is often associated with the "is-a" relationship or inclusion relationship. It is used to establish hierarchies and classifications within a type system. For example, in programming languages, a class hierarchy can be defined with subclasses inheriting from a superclass. Here, the subclasses are subtypes of the superclass.
The subtyping relationship can also be used to establish type compatibility, allowing for type assignment and type checking. A subtype is considered compatible with its supertype because it can fulfill all the contracts and obligations of the supertype.
Subtyping is a fundamental concept in type systems and plays a key role in achieving code reuse, modularity, and abstraction. It promotes flexibility, extensibility, and polymorphism, making type systems more expressive and allowing for more modular and reusable code.
Etymology of SUBTYPING
The word "subtyping" is derived from the term "subtype". The etymology of "subtype" can be traced back to the combination of two words: "sub", meaning "under" or "below", and "type", which refers to a category or classification. Therefore, "subtyping" essentially means forming a secondary or more specific type within a broader or more general type. It is commonly used in fields such as computer science and linguistics to describe the relationship between different types or categories.
