For concatenation of general lists, see append.

In computer programming, string concatenation is the operation of joining two character strings end to end. For example, the strings "foo" and "bar" may be concatenated to give "foobar". In many programming languages, string concatenation is a binary infix operator.

For example, the following expression uses the "+" symbol as the concatenation operator:

print "Hello " + "World";

Different languages

Different languages use different operators. Most languages use the plus sign ("+") though several deviate from this norm.

Examples

Operator	Symbol name	Language
+	plus sign	ActionScript, BASIC, C++, C#, Java, JavaScript, Pascal, Python, Ruby, Windows PowerShell, SQL, GML
&	ampersand	Ada, AppleScript, VHDL, Visual Basic
.	dot	Perl (before version 6), PHP
~	tilde	Perl 6
//	double slash	Fortran
||	double vertical bar	REXX, SQL, Icon
$+	dollar plus	mIRC Scripting Language

For a more detailed comparison, please see the concatenation comparison article.

Programming conventions

Assignment

Many languages, such as PHP and JavaScript have a variant of the assignment operator that allows concatenation and assignment to a variable in one statement.

For example, in PHP and Perl: //Example 1 (concatenation operator ".") $var = "Hello "; $var = $var . "World";

//Example 2 (combined assignment and concatenation ".=") $var = "Hello "; $var .= "World";

Both examples produce the same result.

Interpolation

Some languages, (such as Perl, PHP, and most Unix shells), support variable interpolation as an alternative form of string concatenation.

For example, in Perl, the concatenation syntax:

my $stringVar; $stringVar = "World"; print "Hello " . $stringVar;

can be substituted with the string literal syntax:

my $stringVar; $stringVar = "World"; print "Hello $stringVar";

since double quoted string literals in Perl indicate scalar variables with the dollar sign ($) scalar sigil.

See also

• Formal language

External links

• Concatenation of languages (different from concatenation on strings)