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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)".
A spreadsheet's concatenate ("&") function is used to assemble a complex text string—in this example, XML code for an SVG "circle" element. In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball".
In object-oriented languages, string functions are often implemented as properties and methods of string objects. In functional and list-based languages a string is represented as a list (of character codes), therefore all list-manipulation procedures could be considered string functions.
The cast operator is not overloadable, but one can write a conversion operator method which lives in the target class. Conversion methods can define two varieties of operators, implicit and explicit conversion operators. The implicit operator will cast without specifying with the cast operator (()) and the explicit operator requires it to be used.
Most languages, such as C#, Java [15] and Perl, do not support implicit string literal concatenation, and instead require explicit concatenation, such as with the + operator (this is also possible in D and Python, but illegal in C/C++ – see below); in this case concatenation may happen at compile time, via constant folding, or may be deferred ...
String homomorphisms are monoid morphisms on the free monoid, preserving the empty string and the binary operation of string concatenation. Given a language , the set () is called the homomorphic image of . The inverse homomorphic image of a string is defined as
In the fourth and fifth cases, list concatenation must be invoked. In the last case, string concatenation must be invoked. Thus, the name + actually refers to three or four completely different functions. This is an example of overloading or more specifically, operator overloading. Note the ambiguity in the string types used in the last case.
Various operations, such as copying, concatenation, tokenization and searching are supported. For character strings, the standard library uses the convention that strings are null-terminated: a string of n characters is represented as an array of n + 1 elements, the last of which is a "NUL character" with numeric value 0.