Programming idiom
A programming idiom is a means of expressing a recurring construct in one or more programming languages. Generally speaking, a programming idiom is an expression of a simple task or algorithm 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 in to a programming language. The term can be used more broadly, however, to refer to complex algorithms or programming design patterns.
Knowing the idioms associated with a programming language and how to use them is an important part of gaining fluency in that language.
Examples of Simple Idioms
Incrementing a counter
In a language like Basic, the code to increment a counter by one is mundane:
i = i + 1
The C programming language and many others derived from it have language-specific features that make this code shorter:
i += 1; /* i = i + 1; */
++i; /* same */
Pascal, as a keyword centric language, contains a built in procedure for the same operation:
i := i + 1;
Inc(i); (* same *)
These are the idiomatic ways of "adding one to a counter".
Swapping values between variables
In many languages, code for swapping the values in two variables looks like the following:
temp = a;
a = b;
b = temp;
In Perl, the list assignment syntax allows a more succinct expression:
($a, $b) = ($b, $a);
Infinite loop
The code used to write an infinite (nonterminating) loop varies widely between different programming languages, although it often takes the form of a while loop where the test condition is always true. In Pascal, for example:
while true do begin
do_something();
end;
There are several ways to write an infinite loop in C, including a loop very similar to the Pascal example, but the following idiom uses the unusual appearance of the empty for loop condition to draw attention visually to the loop:
for (;;) {
do_something();
}
Perl allows the C syntax above, but supports some other syntax as well. For example:
do_something() while (1); # Succinct one-line infinite loop
# Using a "naked block" and the redo operator
{
do_something();
redo;
}