Regular expression
Summary
Description what this documentation is about
History of Regular Expressions
Regular Expressions, or regexes in short, is a defined sequence of characters that specify a search pattern. These expressions are used by search machines like a search engine for optimized string searching. The concept of regular expressions arose in the 1950 by the mathematician Stephen Cole Kleene. Kleene described regular languages wit the usage of his mathematical notation called regular events. His notation got used for automata theory and the classification and description of formal languages. With the Rise of Computers many more syntaxes for writing regular expressions got developed. The most popular today are the POSIX standard and the Perl Compatible Regular Expressions (PCRE). Today regexes are implemented into many programming languages like PHP, Python and Java. Furthermore, companies started to produce hardware, FPGA and GPU implementation of PCRE to overcome the performance which is possible by CPUs.
Definition of Regular Expressions
Regular expression gets used to create a pattern that defines the regular language. A finite automata can inspect if the inputted word belongs to the regular language which gets defined by the created pattern.
Syntax of Regular Expressions
References
- Konzepte der Informatik von Peter Lory gelehrt an der FH-Campus Wien
- https://en.wikipedia.org/wiki/Regular_expression
- https://en.wikipedia.org/wiki/Perl_Compatible_Regular_Expressions
- https://www.w3schools.com/python/python_regex.asp
- https://docs.python.org/3/library/re.html