MORE APPLICATIONS OF REGULAR EXPRESSION. By Venkata Sai Pundamalli id:

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1 MORE APPLICATIONS OF REGULAR EXPRESSION By Venkata Sai Pundamalli id:

2 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

3 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,. }

4 Regular Expressions used in APPLICATIONS Apache HTTP Server Microsoft Visual Studio Netbeans Notepad++ LibreOffice Calc Oracle Database Python Sublime Text LANGUAGES.NET C++ D Java JavaScript Perl PHP Ruby

5 Applications of Regular Expression 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.

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

7 Examples of ereg in PHP: <?php $string = "abcd"; $string1 = ereg("^a",$string); if($string1==1) echo "TRUE"; else echo "FALSE";?> Output: TRUE <?php $string = "abcd"; $string1 = ereg("bc$",$string); if($string1==1) echo "TRUE"; else echo "FALSE";?> Output: FALSE

8 Contd., <?php $string = "this is sample"; $string = ereg_replace("^", "<br />", $string); echo $string;?> <?php $string = "this is sample \nwhich is also sample"; echo $string; echo "\nafter Replacement ::\n"; $string = ereg_replace("\n", "", $string); echo $string;?> Output: <br />this is sample Output: this is sample which is also sample After Replacement :: this is sample which is also sample

9 b. Regular Expression in Databases Oracle Database implementation of Regular Expressions SQL Element REGEXP_LIKE REGEXP_COUNT REGEXP_REPLACE Description It s a condition used to match the given pattern It s a function which returns number of times the given pattern appears in the given string It s a function which searches for a pattern in a character column and replace each occurrence of that pattern with the specified string

10 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) '); INSERT INTO contacts (p_number) VALUES('(650) ');

11 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

12 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 a A u s t r a l i a B e l g i u m B r a z i l C a n a d a

13 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_people ORDER BY "names"; names names after regexp Harry S. Truman Truman, Harry S. John Quincy Adams Adams, John Quincy John Adams John Adams John Quincy Adams John Quincy Adams John_Quincy_Adams John_Quincy_Adams

14 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.

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18 References: #ADFNS #CHDJAGEF

19 Thank You Any Queries???