Regular expression - Revision history

Cskallak: /* Summary */

2020-04-01T07:35:31Z

Summary

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	== Summary ==		== Summary ==

	Description what this documentation ~~is about~~		Description what this documentation sums up regular expressions in different Standards and gives an introduction into Python RegEx.

	== History of Regular Expressions ==		== History of Regular Expressions ==

Ikramer: /* Validation of Regular Expressions with Online Tools */

2020-03-31T15:52:18Z

Validation of Regular Expressions with Online Tools

← Older revision		Revision as of 15:52, 31 March 2020
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	== Validation of Regular Expressions with Online Tools ==		== Validation of Regular Expressions with Online Tools ==
	Reading and validating long regular expression may get exhausting sometimes, there exist online tools which facilitate the parsing and testing process. Most of these tools offer Javascript and PCRE for regular expression either used at the client in the browser or on the server side.		Reading and validating long regular expression may get exhausting sometimes, there exist online tools which facilitate the parsing and testing process. Most of these tools offer Javascript and PCRE for regular expression either used at the client in the browser or on the server side.
	~~Example~~ of online tester und debugger:
			Examples of online regular expression tester und debugger:
	* https://regex101.com/		* https://regex101.com/
	* https://www.freeformatter.com/regex-tester.html		* https://www.freeformatter.com/regex-tester.html

Ikramer at 15:51, 31 March 2020

2020-03-31T15:51:15Z

← Older revision		Revision as of 15:51, 31 March 2020
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	\| Returns the matched part of the string		\| Returns the matched part of the string
	\|}		\|}

			== Validation of Regular Expressions with Online Tools ==
			Reading and validating long regular expression may get exhausting sometimes, there exist online tools which facilitate the parsing and testing process. Most of these tools offer Javascript and PCRE for regular expression either used at the client in the browser or on the server side.
			Example of online tester und debugger:
			* https://regex101.com/
			* https://www.freeformatter.com/regex-tester.html
			* https://www.regextester.com/

	== References ==		== References ==

Ikramer at 15:25, 31 March 2020

2020-03-31T15:25:48Z

← Older revision		Revision as of 15:25, 31 March 2020
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	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.		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.		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.		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 problems which some applications cause when using CPUs.

	== Definition of Regular Expressions ==		== Definition of Regular Expressions ==
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	b) The two regular expressions α and β are equivalent in character α ≡ β if L(α) = L(β)		b) The two regular expressions α and β are equivalent in character α ≡ β if L(α) = L(β)

	== Regular expressions and ~~deterministic finite automaton~~ (DFA) ==		== Regular expressions and Deterministic Finite Automaton (DFA) ==

	By using a regex processor, the regular expression translated into an internal representation. One possible approach is to use the Thompson's construction algorithm to develop nondeterministic finite automaton (NFA) that gets translated into a deterministic finite automaton (DFA), which only accepts words based on the regular expression.		By using a regex processor, the regular expression translated into an internal representation. One possible approach is to use the Thompson's construction algorithm to develop nondeterministic finite automaton (NFA) that gets translated into a deterministic finite automaton (DFA), which only accepts words based on the regular expression.
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	== POSIX Standard ==		== POSIX Standard ==

	There ~~atre~~ three sets of syntaxes defined IEEE POSIX standard. The Basic Regular Expressions (BRE), Extended Regular Expressions (ERE) and the Simple Regular Expressions (SRE). The Simple Regular Expressions syntax is deprecated but the other two provide backwards capabilities.		There are three sets of syntaxes defined IEEE POSIX standard. The Basic Regular Expressions (BRE), Extended Regular Expressions (ERE) and the Simple Regular Expressions (SRE). The Simple Regular Expressions syntax is deprecated but the other two provide backwards capabilities.

	=== POSIX basic and extended Semantics ===		=== POSIX basic and extended Semantics ===
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	== Perl Compatible Regular Expressions (PCRE) ==		== Perl Compatible Regular Expressions (PCRE) ==

	PCRE is library that implements a regular expression engine. The library is inspired of the ~~Pearl~~ programming language and is written in c. The library is ~~Opertings~~ system independent and gets distributed with an POSIX C wrapper.		PCRE is a library that implements a regular expression engine. The library is inspired of the Perl programming language and is written in c. The library is Operating system independent and gets distributed with a POSIX C wrapper.

	=== Perl Compatible Regular Expressions Semantics ===		=== Perl Compatible Regular Expressions Semantics ===

Cskallak: /* Regular Expressions in Python */

2020-03-28T17:37:04Z

Regular Expressions in Python

← Older revision		Revision as of 17:37, 28 March 2020
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	\|-		\|-
	\| search()		\| search()
	\| Searches a ~~sting~~ and returns the match object		\| Searches a string and returns the match object
	\|-		\|-
	\| split()		\| split()

Cskallak: /* Regular expressions and deterministic finite automaton (DFA) */

2020-03-28T15:59:15Z

Regular expressions and deterministic finite automaton (DFA)

← Older revision		Revision as of 15:59, 28 March 2020
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	Speaks the same language of the following DFA:		Speaks the same language of the following DFA:

			[[File:RegularExpressions_Endlicher_automat.jpg\|600px]]

	''''' Insert image '''''		''''' Insert image '''''

Cskallak at 15:56, 28 March 2020

2020-03-28T15:56:54Z

← Older revision		Revision as of 15:56, 28 March 2020
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	[[Category:~~Basics~~]]		[[Category:Basic]]

Cskallak: /* Regular Expressions in Python */

2020-03-28T15:42:34Z

Regular Expressions in Python

← Older revision		Revision as of 15:42, 28 March 2020
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	Python comes with the built in RegEx Module which can be used by the line import re. The module can process Unicode as well as 8-bit strings.		Python comes with the built in RegEx Module which can be used by the line import re. The module can process Unicode as well as 8-bit strings.

	=== RegEx Modul Metacharacters: ===		=== RegEx Modul Metacharacters ===

	{\| class="wikitable"		{\| class="wikitable"
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	\|}		\|}

	=== Character Sets: ===		=== Character Sets ===

	{\| class="wikitable"		{\| class="wikitable"
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	\|}		\|}

	=== RegEx Modul functions: ===		=== RegEx Modul functions ===

	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-
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	\|}		\|}

	=== Match object: ===		=== Match object ===

	{\| class="wikitable"		{\| class="wikitable"

Cskallak: /* Match object: */

2020-03-28T15:38:58Z

Match object:

← Older revision		Revision as of 15:38, 28 March 2020
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	\| Returns the matched part of the string		\| Returns the matched part of the string
	\|}		\|}

			== References ==

	* Konzepte der Informatik von Peter Lory gelehrt an der FH-Campus Wien		* Konzepte der Informatik von Peter Lory gelehrt an der FH-Campus Wien

Cskallak: /* Regular Expressions in Python */

2020-03-28T15:38:01Z

Regular Expressions in Python

@@ Line 194: / Line 194: @@
 |}
-Character Sets:
+=== Character Sets: ===
-RegEx Modul functions:
+{| class="wikitable"
-Match object:
+=== RegEx Modul functions: ===
 * Konzepte der Informatik von Peter Lory gelehrt an der FH-Campus Wien