![]() Most implementations work with a special regex engine that parses and interprets the listed regular expressions and checks resources for instances. Regular characters can be in front or behind the metacharacters, their formal meaning will then be different. ![]() Metacharacters are instructions for the processing software. The metacharacters are specified operations such as alternation |, linking () and and repeats with *, + and?. The characters are recorded in the character set (the alphabet) which contains, for example, numbers, letters and commas. Generally, (terminal) characters and metacharacters are distinguished. The differences are sometimes due to the fact that individual characters and especially metacharacters (control characters) are used in a programming language. These notations are called shell pattern name, BRE (Basic Regular Expressions) and ERE (Extended Regular Expressions). There are different notations in different programming languages. The possible regular expressions depend on the notation. In Google Analytics regular expressions are also utilized to filter traffic sources, define segments and separate detailed report data from other data. Or in EditPad, Emacs and Notepad ++ as a search and replace function in text editors. NET or JavaScript as elements of a library. Regex can be used depending on their implementation in several programming languages, environments and text editors, for example, in Perl, PHP. ![]() Regular expressions are now used in various fields to simplify operations, which would otherwise be very work-intensive and time-consuming. This and other works are today fundamental basics in theoretical computer science. In 1956 he used notations of regular amounts in an essay on the representation of events in neural networks and finite automata. The logician and mathematician Stephen Kleene is considered to be the founder of regex.
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