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A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.. In POSIX extended regular expressions, there are 14 metacharacters that must be escaped — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ...
The primary regex crate does not allow look-around expressions. There is an Oniguruma binding called onig that does. SAP ABAP: SAP.com: Proprietary: Tcl: tcl.tk: Tcl/Tk License (BSD-style) Tcl library doubles as a regular expression library. Wolfram Language: Wolfram Research: Proprietary: usable for free on a limited scale on the Wolfram ...
More generally, an equation E=F between regular-expression terms with variables holds if, and only if, its instantiation with different variables replaced by different symbol constants holds. [30] [31] Every regular expression can be written solely in terms of the Kleene star and set unions over finite words. This is a surprisingly difficult ...
Brackets: Angle bracket, Parenthesis • Bullet: Interpunct ‸ ⁁ ⎀ Caret (proofreading) Caret (computing) (^) Chevron (non-Unicode name) Caret, Circumflex, Guillemet, Hacek, Glossary of mathematical symbols ^ Circumflex (symbol) Caret (The freestanding circumflex symbol is known as a caret in computing and mathematics) Circumflex ...
Caret (from Latin caret 'there is lacking') [3] is the name used familiarly for the character ^ provided on most QWERTY keyboards by typing ⇧ Shift+6.The symbol has a variety of uses in programming and mathematics.
Escape characters are part of the syntax for many programming languages, data formats, and communication protocols. For a given alphabet an escape character's purpose is to start character sequences (so named escape sequences ), which have to be interpreted differently from the same characters occurring without the prefixed escape character.
An advanced regexp uses the metacharacters to program general string patterns. It finds everything, even pieces and parts of words, conveying no notion of "words", but only that of a string of characters in a sequence. Metacharacters are interpreted unless quoted by a backslash, double quotes, or square brackets. See the section on regex.
/ is special because it indicates the end of the regex. For example, insource:/yes/no/ is treated the same as insource:/yes/ no (because the keyword search for no/ ignores punctuation). The / character must be backslash-escaped everywhere it appears inside a regex – even inside square brackets or quotation marks.. matches any single character.