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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.
Microsoft Excel allows both "&" and the function "=CONCATENATE(X,Y)". Rust has the concat! macro and the format! macro, of which the latter is the most prevalent throughout the documentation and examples.
In programming, string concatenation generally occurs at run time, as string values are typically not known until run time. However, in the case of string literals, the values are known at compile time, and thus string concatenation can be done at compile time, either via string literal concatenation or via constant folding , a potential run ...
String concatenation is an associative, but non-commutative operation. The empty string ε serves as the identity element ; for any string s , ε s = s ε = s . Therefore, the set Σ * and the concatenation operation form a monoid , the free monoid generated by Σ.
The properties of concatenative languages are the result of their compositional syntax and semantics: The reduction of any expression is the simplification of one function to another function; it is never necessary to deal with the application of functions to objects.
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
If is a set of strings, then is defined as the smallest superset of that contains the empty string and is closed under the string concatenation operation. If V {\\displaystyle V} is a set of symbols or characters, then V ∗ {\\displaystyle V^{*}} is the set of all strings over symbols in V {\\displaystyle V} , including the empty string ε ...
String interpolation, like string concatenation, may lead to security problems. If user input data is improperly escaped or filtered, the system will be exposed to SQL injection, script injection, XML external entity (XXE) injection, and cross-site scripting (XSS) attacks. [4] An SQL injection example: query = "SELECT x, y, z FROM Table WHERE ...