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AWK uses the empty string: two expressions adjacent to each other are concatenated. This is called juxtaposition. Unix shells have a similar syntax. Rexx uses this syntax for concatenation including an intervening space.
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.
In many programming languages, string concatenation is a binary infix operator, and in some it is written without an operator. This is implemented in different ways: Overloading the plus sign + Example from C#: "Hello, " + "World" has the value "Hello, World". Dedicated operator, such as . in PHP, & in Visual Basic [1] and || in SQL.
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
The Spring Framework is an application framework and inversion of control container for the Java platform. [2] The framework's core features can be used by any Java application, but there are extensions for building web applications on top of the Java EE (Enterprise Edition) platform.
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 ...