Writing Regular Expressions

A regular expression is a precise pattern that provides a very efficient way to specify and recognize strings of text. A combination of various characters along with the text to be searched for generates a regular expression.

Tally.Developer 9 uses regular expression to search for text based on specified patterns. These patterns are a combination of special characters and the text that needs to be searched for.

Some examples are given in the table below:

Character	Description	Example
^	Used to match the start of a line	^Local This expression will search for all lines that start with Local
$	Used to match the end of a line	$Tally This expression will search for all lines that end with Tally
.	Used to match or replace a Single Character	F.rm This expression will search for all terms which start with F, have one character in the middle and end with rm
*	Searches for zero or more occurrences of the preceding character	Lo*cal This expression will search for Lcal, Local, Loocal, Looocal...
+	Searches for one or more occurrences of the preceding character	Lo+cal This expression will search for all terms Local, Loocal, Looocal.....
\x	Used to search for a character which otherwise may have another meaning	\ This expression will search for locations where '[' is present.
\<	Used to match the start of a word	\<Ad This expression will search for all terms that begin with Ad
\>	Used to match the end of a word	\>ed This expression is used for all terms that end with ed
\(	Used to denote the start of a region for tagging a match
\)	Used to denote the end of a region for tagging a match
[.....]	Denotes a set of possible character matches	[A-z] It will search for terms with characters between a to z
[^...]	Used to indicate complement of a set of characters	[^A-d] lt will not search for terms with characters between a to d
\d	Used to match a digit	Tally$\d+$ It will search for terms with a combination of text and numbers like Tally1, Tally512
\s	Used to match a white space character	Tally\s It will search for terms with Tally and a line feed character after it like space or tab

Combination of Characters

To make a search more refined, we use a combination of characters. Any of the characters given above can be used in conjunction with each other to get a thoroughly enhanced output. Given below are a few examples to explain how this can be done.

Regular Expression	Result
^Tally$[abc]$	This will search for terms which start at the beginning of the line and consist of Tallya, Tallyb or Tallyc.
Tal*y$\d+$	This will search for terms which have zero or more occurrences of l between a and y and any digits after the text.
^.$	This will search for lines containing only a single character.
^Pa?	This will search for any term which has a P OR Pa at the beginning of the line.

From the above examples we can see that regular expression is the term used to describe a codified method of searching which enables fast and responsive searches.

Regular Expression	Result
^Tally\([abc]\)	This will search for terms which start at the beginning of the line and consist of Tallya, Tallyb or Tallyc.
Tal*y\(\d+\)	This will search for terms which have zero or more occurrences of l between a and y and any digits after the text.
^.$	This will search for lines containing only a single character.
^Pa?	This will search for any term which has a P OR Pa at the beginning of the line.