Abstraction principle (computer programming)

In software engineering and programming language theory, the abstraction principle (or the principle of abstraction) is a basic dictum that aims to reduce duplication of information in a program (usually with emphasis on code duplication) whenever practical by making use of abstractions provided by the programming language or software libraries . The principle is sometimes stated as a recommendation to the programmer, but sometimes stated as a requirement of the programming language, assuming it is self-understood why abstractions are desirable to use. The origins of the principle are uncertain; it has been reinvented a number of times, sometimes under a different name, with slight variations. When read as recommendations to the programmer, the abstraction principle can be generalized as the "don't repeat yourself" (DRY) principle, which recommends avoiding the duplication of information in general, and also avoiding the duplication of human effort involved in the software development process. As a recommendation to the programmer, in its formulation by Benjamin C. Pierce in Types and Programming Languages (2002), the abstraction principle reads (emphasis in original): Each significant piece of functionality in a program should be implemented in just one place in the source code. Where similar functions are carried out by distinct pieces of code, it is generally beneficial to combine them into one by abstracting out the varying parts. As a requirement of the programming language, in its formulation by David A. Schmidt in The structure of typed programming languages (1994), the abstraction principle reads:. The phrases of any semantically meaningful syntactic class may be named. The abstraction principle is mentioned in several books. Some of these, together with the formulation if it is succinct, are listed below. Alfred John Cole, Ronald Morrison (1982) An introduction to programming with S-algol: "[Abstraction] when applied to language design is to define all the semantically meaningful syntactic categories in the language and allow an abstraction over them".