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The strings over an alphabet, with the concatenation operation, form an associative algebraic structure with identity element the null string—a free monoid. Sets of strings with concatenation and alternation form a semiring, with concatenation (*) distributing over alternation (+); 0 is the empty set and 1 the set consisting of just the null ...
String functions common to many languages are listed below, including the different names used. The below list of common functions aims to help programmers find the equivalent function in a language. Note, string concatenation and regular expressions are handled in separate pages.
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)".
String concatenation is an associative, but non-commutative operation. The empty string ε serves as the identity element; for any string s, εs = sε = s. Therefore, the set Σ * and the concatenation operation form a monoid, the free monoid generated by Σ.
In Common Lisp, the ampersand is the prefix for lambda list keywords. [29] Ampersand is the string concatenation operator in many BASIC dialects, AppleScript, Lingo, HyperTalk, and FileMaker. [citation needed] In Ada it applies to all one-dimensional arrays, not just strings. [citation needed]
An identifier is the name of an element in the code. There are certain standard naming conventions to follow when selecting names for elements. Identifiers in Java are case-sensitive. An identifier can contain: Any Unicode character that is a letter (including numeric letters like Roman numerals) or digit. Currency sign (such as ¥).
A string is a finite sequence of characters. The empty string is denoted by .The concatenation of two string and is denoted by , or shorter by .Concatenating with the empty string makes no difference: = =.
In Miranda, this right-fold, from Hughes (1989:5-6), has the same semantics (by example) as the Scheme implementation above, for two arguments. append a b = reduce cons b a Where reduce is Miranda's name for fold, and cons constructs a list from two values or lists. For example,