Programming idiom


A programming idiom or code idiom is expressing a special feature of a recurring construct in one or more programming languages. Developers recognize programming idioms by associating and giving meaning to one or more code fragments. The idiom can be seen as a concept underlying a pattern in code, which is represented in implementation by contiguous or scattered code fragments. These fragments are available in several programming languages, frameworks or even libraries. Generally speaking, a programming idiom is a natural language expression of a simple task, algorithm, or data structure that is not a built-in feature in the programming language being used, or, conversely, the use of an unusual or notable feature that is built into a programming language. Furthermore, the term can be used more broadly, to refer to complex algorithms or programming design patterns in terms of implementation and omitting design rationale.
Knowing the idioms associated with a programming language and how to use them is an important part of gaining fluency in that language, and transferring knowledge in the form of analogies from one language or framework to another.
Adverbial or adjectival use of the term often takes the meaning of using a programming language in a typical way. For example, an idiomatic way to manage dynamic memory in C would be to use the C standard library functions malloc and free. Such code would be well intelligible to somebody familiar with C, and would be unlikely to cause issues with software portability to different computing platforms. On the other hand, if the code would forgo the use of these standard functions, and instead request memory using the system call sbrk to achieve some special behaviour, that could be considered non-idiomatic; it would require more effort to understand and not be portable to non-Unix-like systems.

Examples of simple idioms

Printing Hello World

One of the most common starting points to learn a program or notice the syntax differences between a known language and a new one.
It has several implementations, among them the code fragments for C++:

std::cout << "Hello World\n";

For Java:

System.out.println;

Inserting an element in an array

This idiom helps developers understand how to manipulate collections in a given language, particularly inserting an element x at a position i in a list s and moving the elements to its right.
Code fragments:
For Python:

s.insert
For JavaScript:

s.splice;
For Perl:

splice