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In computer science, a literal is a textual representation (notation) of a value as it is written in source code. [1] [2] Almost all programming languages have notations for atomic values such as integers, floating-point numbers, and strings, and usually for Booleans and characters; some also have notations for elements of enumerated types and compound values such as arrays, records, and objects.
A 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" is a string literal with value foo. Methods such as escape sequences can be used to avoid the ...
COBOL uses the STRING statement to concatenate string variables. MATLAB and Octave use the syntax "[x y]" to concatenate x and y. Visual Basic and Visual Basic .NET can also use the "+" sign but at the risk of ambiguity if a string representing a number and a number are together. Microsoft Excel allows both "&" and the function "=CONCATENATE(X,Y)".
Constants are usually defined by enum types or constant parameters that are also written this way. Class and other object type declarations are UpperCamelCase. As of Swift 3.0 there have been made clear naming guidelines for the language in an effort to standardise the API naming and declaration conventions across all third party APIs. [44]
In the program's source code, this message would likely appear as a string literal. User-entered text, like "I got a new job today" as a status update on a social media service. Instead of a string literal, the software would likely store this string in a database. Alphabetical data, like "AGATGCCGT" representing nucleic acid sequences of DNA. [3]
[3] Dynamically valued constants originated as a language feature with ALGOL 68. [3] Studies of Ada and C++ code have shown that dynamically valued constants are used infrequently, typically for 1% or less of objects, when they could be used much more, as some 40–50% of local, non-class objects are actually invariant once created.
Constant folding is the process of recognizing and evaluating constant expressions at compile time rather than computing them at runtime. Terms in constant expressions are typically simple literals, such as the integer literal 2, but they may also be variables whose values are known at compile time. Consider the statement:
Two types of literal expression are usually offered: one with interpolation enabled, the other without. Non-interpolated strings may also escape sequences, in which case they are termed a raw string, though in other cases this is separate, yielding three classes of raw string, non-interpolated (but escaped) string, interpolated (and escaped) string.