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From biology to programming languages: What's the surprising story behind polymorphism?
In programming language theory, polytype is a powerful concept that allows a symbol to represent multiple different types. This concept is not only applied to object-oriented programming, but it is also deeply rooted in the principles of biology. It is surprising that there is such a deep connection between the two. By exploring the different forms of polymorphism and its impact on software development, we may be able to gain a clearer understanding of the stories behind these technologies.
In biology, some organisms or species can take on multiple different forms or stages, and this phenomenon is at the heart of polymorphism.
The main forms of polytype include three categories: immediate polytype, parameter polytype and subtype polytype. Each of these forms has its own unique characteristics and applications, and has different implementation methods in different programming languages.
Instant polymorphism
Immediate polytyping means that a function exhibits different behaviors depending on the parameter type. This is especially obvious in function overloading or operator overloading. In programming languages such as Java, similar function names may be used to achieve seemingly the same operation effects, but in fact, these functions are different.
In a dynamically typed language, the situation is more complicated because the correct function call needs to be determined at runtime.
Parameter polytype
This form of polytyping allows programmers to write functions or data types that can handle different types of values generically, without relying on specific types. It makes programming languages more expressive while maintaining complete static type safety. Parametric polytyping, jumping between functions and data types, is a common feature in functional programming languages.
A function that can be applied to different types is called a polytype function, and a data type that can appear as a generalized type is called a polytype data type.
Subtype polytype
Subtype polytype, also known as containment polytype, describes the restrictions on the range of types that can be used in specific situations. This means that a function can receive an object of type T but still run correctly if it uses an object of type S (a subtype of T). This shows how inheritance and polytyping can be used to increase flexibility in programs.
Subtype polytyping can be used by designing functions to receive supertypes, allowing objects of any subtype to be passed in.
Multiple installation methods
The implementation of polytypes can be divided into static and dynamic polytypes. Static polytype selection is implemented at compile time and generally performs faster, but requires additional compiler support. Dynamic polytypes are selected during runtime, providing more flexibility but accompanied by reduced performance. This requires program designers to consider the trade-off between runtime execution efficiency and flexibility in implementation.
Static polytypes usually appear in immediate polytypes and parameter polytypes, while dynamic polytypes are usually used in the implementation of subtype polytypes.
The introduction of polytypes makes programming no longer restricted to specific data types, allowing developers to create adaptable systems more flexibly. However, whether from a programming perspective or a biological perspective, there are deeper philosophical considerations and potential significance for future development behind polymorphism. On this basis, we can’t help but think: How will multi-type technologies continue to evolve in the near future and affect the way we live and work?
