In
computer science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
, a literal is a textual representation (notation) of a
value as it is written in
source code
In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer.
Since a computer, at base, only ...
.
Almost all programming languages have notations for atomic values such as
integer
An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...
s,
floating-point numbers, and
string
String or strings may refer to:
*String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects
Arts, entertainment, and media Films
* ''Strings'' (1991 film), a Canadian anim ...
s, and usually for
Booleans and
characters; some also have notations for
elements of enumerated types and compound values such as
arrays
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
,
records, and
objects. An
anonymous function is a literal for the
function type.
In contrast to literals,
variables or
constants are symbols that can take on one of a class of fixed values, the constant being constrained not to change. Literals are often used to initialize variables; for example, in the following, 1 is an integer literal and the three letter string in "cat" is a string literal:
int a = 1;
string s = "cat";
In
lexical analysis
Lexical tokenization is conversion of a text into (semantically or syntactically) meaningful ''lexical tokens'' belonging to categories defined by a "lexer" program. In case of a natural language, those categories include nouns, verbs, adjectives ...
, literals of a given type are generally a token type, with a grammar rule, like "a
string of digits" for an integer literal. Some literals are specific
keywords, like
true for the Boolean literal "true".
In some
object-oriented languages (like
ECMAScript
ECMAScript (; ES) is a standard for scripting languages, including JavaScript, JScript, and ActionScript. It is best known as a JavaScript standard intended to ensure the interoperability of web pages across different web browsers. It is stan ...
), objects can also be represented by literals. Methods of this object can be specified in the object literal using
function literals. The brace notation below, which is also used for array literals, is typical for object literals:
Literals of objects
In
ECMAScript
ECMAScript (; ES) is a standard for scripting languages, including JavaScript, JScript, and ActionScript. It is best known as a JavaScript standard intended to ensure the interoperability of web pages across different web browsers. It is stan ...
(as well as its implementations
JavaScript
JavaScript (), often abbreviated as JS, is a programming language and core technology of the World Wide Web, alongside HTML and CSS. Ninety-nine percent of websites use JavaScript on the client side for webpage behavior.
Web browsers have ...
or
ActionScript
ActionScript is an object-oriented programming language originally developed by Macromedia Inc. (later acquired by Adobe). It is influenced by HyperTalk, the scripting language for HyperCard. It is now an implementation of ECMAScript (mean ...
), an object with methods can be written using the object literal like this:
var newobj = ;
newobj.method1();
newobj.method2();
These object literals are similar to
anonymous classes in other languages like
Java
Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...
.
The
JSON
JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consi ...
data interchange format is based on a subset of the JavaScript object literal syntax, with some additional restrictions (among them requiring all keys to be quoted, and disallowing functions and everything else except data literals). Because of this, ''almost'' every valid JSON document (except for some subtleties with escaping) is also valid JavaScript code, a fact exploited in the
JSONP technique.
See also
*
Character literal
*
Function literal
*
Here document – a file literal or stream literal
*
Hexadecimal floating-point literal
*
Integer literal In computer science, an integer literal is a kind of literal (computer programming), literal for an integer (computer science), integer whose Value (computer science), value is directly represented in source code. For example, in the assignment stat ...
*
String literal
string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo", where , "foo ...
References
{{DEFAULTSORT:Literal (Computer Science)
Programming constructs