MORE APPLICATIONS OF REGULAR EXPRESSION

ByVenkata Sai Pundamalli

E-mail id: vpundama@kent.edu

CONTENTS

Introduction to Regular Expression

Regular Expressions used in

Applications of Regular Expression

a. RE in PHP

b. RE in Databases

c. RE in Voice Recognition

Regular Expression

A regular expression is an algebraic formula whose value is a pattern consisting of a set of strings.

Example:

The set of strings over {A-Z,a-z} that contain the word “main”<letter> = A | B | ……. | Z | a | b | ……. | z

<letter>* main <letter>*

Here, <letter>* may or may not contain any combination of strings over {A- Z,a-z}

<letter>* = { ε, a , b, aa, bb, ab, bc, ez, abc, main, part, …. }

Regular Expressions used in

APPLICATIONS LANGUAGES

Apache HTTP Server .NETMicrosoft Visual Studio C++Netbeans DNotepad++ JavaLibreOffice Calc JavaScriptOracle Database PerlPython PHPSublime Text Ruby

a. Regular Expression in PHP

The ereg() function searches a string to match the given pattern, returning true if the pattern is found, and false otherwise. The search is case sensitive

The eregi() function searches a string to match the given pattern, returning true if the pattern is found, and false otherwise. The search is not case sensitive.

Applications of Regular Expression

Difference between ereg and eregi:<?php$string = 'XYZ';if (ereg('z', $string)) { echo "'$string' contains a 'z'"; }else{ echo "'$string' contains a 'Z'!";}?>

OUTPUT

'XYZ' contains a 'Z'!

<?php$string = 'XYZ';if (eregi('z', $string)) { echo "'$string' contains a 'z‘ or ‘Z’"; }else{ echo "'$string' contains a 'Z'!";}?>

OUTPUT

'XYZ' contains a ‘z‘ or ‘Z’!

<?php$string = "abcd";$string1 = ereg("^a",$string);if($string1==1)echo "TRUE";elseecho "FALSE";?>

<?php$string = "abcd";$string1 = ereg("bc$",$string);if($string1==1)echo "TRUE";elseecho "FALSE";?>

Output:TRUE

Output:FALSE

Examples of ereg in PHP:

<?php$string = "this is sample \nwhich is also sample";echo $string;echo "\nAfter Replacement ::\n";$string = ereg_replace("\n", "", $string);echo $string;?>

Output:

this is sample which is also sampleAfter Replacement ::this is sample which is also sample

<?php$string = "this is sample";$string = ereg_replace("^", "<br />", $string); echo $string;?>

Output:

<br />this is sample

Contd.,

b. Regular Expression in Databases

Oracle Database implementation of Regular Expressions

SQL Element Description

REGEXP_LIKE It’s a condition used to match the given patternREGEXP_COUNT It’s a function which returns number of times the given

pattern appears in the given stringREGEXP_REPLACE It’s a function which searches for a pattern in a character

column and replace each occurrence of that pattern with the specified string

For instance,To ensure that phone numbers are entered into the database in a standard format.(XXX) XXX-XXXX

DROP TABLE contacts;CREATE TABLE contacts ( l_name VARCHAR2(30), p_number VARCHAR2(30) CONSTRAINT c_contacts_pnf CHECK (REGEXP_LIKE (p_number, '^\(\d{3}\) \d{3}-\d{4}$')));

INSERT INTO contacts (p_number) VALUES('(650) 555-0100');INSERT INTO contacts (p_number) VALUES('(650)555-0100');

The following example examines the given string. Oracle returns the number of times that the word ‘the’ appears in the sting.

SELECT REGEXP_COUNT ('The example shows how to use the REGEXP_COUNT function.', 'the', 1, 'i') ”REGEXP_COUNT” FROM dual;

REGEXP_COUNT---------------------------------------2

The following example examines country_name. Oracle puts a space after each non-null character in the string.

SELECT REGEXP_REPLACE(country_name, '(.)', '\1 ') "REGEXP_REPLACE" FROM countries;

REGEXP_REPLACE------------------------------------------------A r g e n t i n aA u s t r a l i aB e l g i u mB r a z i lC a n a d a

For each name in the table whose format is "first middle last", we reposition the characters so that the format becomes "last, first middle":

SELECT names "names", REGEXP_REPLACE(names, '^(\S+)\s(\S+)\s(\S+)$', '\3, \1 \2') AS "names after regexp"FROM famous_peopleORDER BY "names";

names names after regexp--------------------------- ---------------------------------Harry S. Truman Truman, Harry S.John Quincy Adams Adams, John QuincyJohn Adams John Adams John Quincy Adams John Quincy AdamsJohn_Quincy_Adams John_Quincy_Adams

c. Regular Expression in voice recognition

A Speech recognition application is capable of launching external applications based on the command we tell to it.

Regular Expression used in this application is:

string command = Regex.Replace(line, "Start", "").Trim();

This application is written in C# with the help of Visual Studio Express.

References:

https://www.cs.rochester.edu/~nelson/courses/csc_173/fa/re.html http://www.tutorialspoint.com/php/php_ereg.htm http://docs.oracle.com/cd/E11882_01/appdev.112/e41502/

adfns_regexp.htm#ADFNS00402 http://docs.oracle.com/cd/B28359_01/appdev.111/b28424/

adfns_regexp.htm#CHDJAGEF http://docs.oracle.com/cd/B12037_01/server.101/b10759/functions115.htm http://www.prodigyproductionsllc.com/articles/programming/simple-speech-

recognition-using-c-part-2/

Thank You

AnyQueries???