Regex processing - Revision history

Alex: /* Look-around subexpressions */

2025-09-04T14:10:34Z

Look-around subexpressions

← Older revision		Revision as of 14:10, 4 September 2025
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	====<b id="lookahead"></b><b id="lookbehind"></b>Look-around subexpressions====		====<b id="lookahead"></b><b id="lookbehind"></b>Look-around subexpressions====
	~~Although~~ <i><b>~~look~~-ahead</b></i> ~~subexpressions in a regex are supported,~~		<i><b>Look-ahead</b></i> and <i><b>look-behind</b></i> subexpressions are supported
	<i><b>look-behind</b></i> subexpressions are ~~'''not'''~~ supported.		as of Model 204 V7.9.
	~~Look-behind specifications begin with <code>(?<=</code> or <code>(?<!</code>~~.

	The ~~only~~ supported parenthesized subexpression sequences that begin		The supported parenthesized subexpression sequences that begin
	with a question mark are the following, which are all non-capturing:		with a question mark are the following, which are all non-capturing:
	<table>		<table>
	<tr><td>(?:</td>		<tr><td>(?:</td>
	<td>Denotes a non-capturing group</td></tr>		<td>Denotes a non-capturing group</td></tr>

	<tr><td>(?=</td>		<tr><td>(?=</td>
	<td>Denotes a positive look-ahead</td></tr>		<td>Denotes a positive look-ahead</td></tr>

	<tr><td>(?!</td>		<tr><td>(?!</td>
	<td>Denotes a negative look-ahead</td></tr>		<td>Denotes a negative look-ahead</td></tr>
			<tr><td>(?<=</td>
			<td>Denotes a positive look-behind</td></tr>
			<tr><td>(?<!</td>
			<td>Denotes a negative look-behind</td></tr>
	</table>		</table>

Alex: /* Look-around subexpressions */

2022-02-24T21:37:08Z

Look-around subexpressions

← Older revision		Revision as of 21:37, 24 February 2022
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	captures <code>aa</code>. </li>		captures <code>aa</code>. </li>
	</ul>		</ul>

			====<b id="backref"></b>Back references====
			<p>
			In Model 204 7.9, back references are supported. For example, the regular expression <code>(....)\1+</code> would match any string where there was a repetition of any two character pair so that in string <code>"My dog said bow-wow-wow-wow-wow!"</code> it would match <code>"-wow-wow-wow-wow"</code>.
			</p>

	====<b id="lookahead"></b><b id="lookbehind"></b>Look-around subexpressions====		====<b id="lookahead"></b><b id="lookbehind"></b>Look-around subexpressions====

Alex: /* Alternatives */

2022-02-24T21:30:33Z

Alternatives

@@ Line 429: / Line 429: @@
 </p>
 An empty alternative (like the <code>|</code>, above, that is followed only by the closing parenthesis) is always True.
 ===Features that affect the whole expression===

Alex: /* Capturing groups */

2022-02-24T21:22:07Z

Capturing groups

← Older revision		Revision as of 21:22, 24 February 2022
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	====Capturing groups====		====Capturing groups====
	<ul>		<ul>
	<li>~~Extraction~~ of <i><b>repeating capture groups</b></i> from a string is		<li>Before Model 204 7.9 extraction of <i><b>repeating capture groups</b></i> from a string is
	different in Perl and SOUL.		different in Perl and SOUL.
	If there are multiple matches by a repeated group, Perl replaces each capture with the next one, ending up with only the final capture.		If there are multiple matches by a repeated group, Perl replaces each capture with the next one, ending up with only the final capture.
	SOUL saves each capture and concatenates them when finished.		In Model 204 7.8 and earlier, SOUL saves each capture and concatenates them when finished.
	<p>		<p>
	For example, if this is the ''regex'': </p>		For example, if this is the ''regex'': </p>
Line 382:		Line 382:
	The resulting capture in SOUL $functions and methods is <code>ABCDEF</code>,		The resulting capture in SOUL $functions and methods is <code>ABCDEF</code>,
	the concatenation of six one-character matches.		the concatenation of six one-character matches.
	In Perl, the resulting capture is <code>F</code>. </p></li>		In Perl, the resulting capture is <code>F</code>. </p>
			<p>
			In Model 204 7.9, capturing group processing was changed to be consistent with Perl and pretty much all regular expression implementations. If one really wants or needs the old behavior, it can usually be achieved by embedding the entire repeated search string in parentheses. On can change the regex above to:
			</p>
			<p class="code">9([A-Z]*)9
			</p>
			<p>
			and <code>ABCDEF</code> would be captured for string <code>"xxx9ABCDEF9yyy"</code>.
			</p>
			</li>

	<li>A subexpression that is a validly formed capturing group		<li>A subexpression that is a validly formed capturing group

Alex: /* SOUL programming considerations */

2022-01-21T17:06:01Z

SOUL programming considerations

← Older revision		Revision as of 17:06, 21 January 2022
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	</ul>		</ul>

	[[Category:Regular ~~Expression Processing~~]]		[[Category:Regular expression processing]]
	[[Category:Overviews]]		[[Category:Overviews]]

Alex: /* SOUL programming considerations */

2022-01-21T17:01:51Z

SOUL programming considerations

← Older revision		Revision as of 17:01, 21 January 2022
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	</ul>		</ul>

			[[Category:Regular Expression Processing]]
	[[Category:Overviews]]		[[Category:Overviews]]

Alex: /* Common regex options */

2022-01-21T16:25:57Z

Common regex options

@@ Line 493: / Line 493: @@
 options available to that function or method.
 <table class="thJustBold">
 <tr><th>I</th>
 <td>Do case-insensitive matching between the input string(s) and the regex. Treat the uppercase and lowercase variants of letters as equivalent. </td></tr>
 <tr><th>M</th>
@@ Line 515: / Line 530: @@
 caret and dollar sign are not metacharacters in C mode. </p></td></tr>
-<tr><th>C</th>
+<tr><th>S</th>
-<td>XML Schema mode. See, below, [[#XML Schema mode|XML Schema mode]]. </td></tr>
+<td>Dot-All mode. If this mode is '''not''' specified, a dot (<code>.</code>), also called a point, matches any single character except X'0D' (carriage return) and X'25' (linefeed). In Dot-All mode, a dot also matches carriage return and linefeed characters. </td></tr>
-<tr><th>G</th>
+<tr><th>T</th>
-<td>Global replacement of matched substrings (for methods and $functions that provide replacement substrings for matched substrings).
+<td>Trace regular expression evaluation. This option, available in Model 204 V7.9 and later, sends trace lines to the terminal, a USE dataset, and/or the audit trail for each atom (essentially, each step) of regular expression processing. This can be useful in determining why a regular expression is producing the results that it does and perhaps provide hints as to how performance of a particular regular expression can be improved.</td></tr>
 </table>

Dme: /* Look-around subexpressions */

2020-02-23T19:07:53Z

Look-around subexpressions

← Older revision		Revision as of 19:07, 23 February 2020
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	</ul>		</ul>

	====Look-around subexpressions====		====<b id="lookahead"></b><b id="lookbehind"></b>Look-around subexpressions====
	Although <i><b>look-ahead</b></i> subexpressions in a regex are supported,		Although <i><b>look-ahead</b></i> subexpressions in a regex are supported,
	<i><b>look-behind</b></i> subexpressions are '''not''' supported.		<i><b>look-behind</b></i> subexpressions are '''not''' supported.
Line 408:		Line 408:
	<td>Denotes a negative look-ahead</td></tr>		<td>Denotes a negative look-ahead</td></tr>
	</table>		</table>

	====Alternatives====		====Alternatives====
	Alternatives (indicated by <code>\|</code>) are evaluated from		Alternatives (indicated by <code>\|</code>) are evaluated from

Dme: /* Online web resources; regex character set */

2019-01-24T11:25:25Z

Online web resources; regex character set

← Older revision		Revision as of 11:25, 24 January 2019
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	If a regex feature is not mentioned below, you should assume it is supported by SOUL to the extent that it is supported in Perl.		If a regex feature is not mentioned below, you should assume it is supported by SOUL to the extent that it is supported in Perl.

	===Online web resources; regex character set===		===<b id="web"></b>Online web resources; regex character set===
	A Google search of 'regex' will yield many pages, and you will find some that are well suited to your task; it is difficult to provide a "one size fits all" recommendation.		A Google search of 'regex' will yield many pages, and you will find some that are well suited to your task; it is difficult to provide a "one size fits all" recommendation.

Dme: /* Online web resources; regex character set */

2019-01-24T11:23:36Z

Online web resources; regex character set

← Older revision		Revision as of 11:23, 24 January 2019
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	A Google search of 'regex' will yield many pages, and you will find some that are well suited to your task; it is difficult to provide a "one size fits all" recommendation.		A Google search of 'regex' will yield many pages, and you will find some that are well suited to your task; it is difficult to provide a "one size fits all" recommendation.

	~~Here~~ is one link that provides a one-page illustration of regex features, ~~without~~ <b>extremely</b> brief indications of their purpose:		However, here is one link that provides a one-page illustration of regex features, with <b>extremely</b> brief indications of their purpose:

	http://web.mit.edu/hackl/www/lab/turkshop/slides/regex-cheatsheet.pdf		http://web.mit.edu/hackl/www/lab/turkshop/slides/regex-cheatsheet.pdf