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Full Discussion: Perl regex help - matching parentheses
Top Forums Shell Programming and Scripting Perl regex help - matching parentheses Post 302207376 by cvp on Thursday 19th of June 2008 05:49:58 PM
Old 06-19-2008
Thanks, but that wasn't my question; I already know how to escape parentheses.
My data is grouped in many variations of parentheses, sometimes doubled or tripled up. I wanted to know if there was a way to match all of those variations with one regex.
More examples:
extract "(bar)" from "(foo (bar))"
extract "(bar)" from "((foo (bar)) baz)"
extract "((foo))" from "(((foo)) bar)"
...etc.
The key thing here is matching the same number of closed parentheses as open parentheses. I just don't want to have to resort to using a stack or doing something like:
Code:
$string =~ /(\(+)[^)]*/;
$regex = ')' x length($1);
$match = $&;
if ($' =~ /$regex/) { $match .= $&; }
else { next; }
# etc.

 

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LEARN ABOUT DEBIAN

stag-diff

STAG-DIFF(1p)						User Contributed Perl Documentation					     STAG-DIFF(1p)

NAME

       stag-diff - finds the difference between two stag files

SYNOPSIS

	 stag-diff -ignore foo-id -ignore bar-id file1.xml file2.xml

DESCRIPTION

       Compares two data trees and reports whether they match. If they do not match, the mismatch is reported.

   ARGUMENTS
       -help|h
	   shows this document

       -ignore|i ELEMENT
	   these nodes are ignored for the purposes of comparison. Note that attributes are treated as elements, prefixed by the containing
	   element id. For example, if you have

	     <foo ID="wibble">

	   And you wish to ignore the ID attribute, then you would use the switch

	     -ignore foo-ID

	   You can specify multiple elements to ignore like this

	     -i foo -i bar -i baz

	   You can also specify paths

	     -i foo/bar/bar-id

       -parser|p FORMAT
	   which parser to use. The default is XML. This can also be autodetected by the file suffix. Other alternatives are sxpr and itext. See
	   Data::Stag for details.

       -report|r ELEMENT
	   report mismatches as they occur on each element of type ELEMENT

	   multiple elements can be specified

       -verbose|v
	   used in conjunction with the -report switch

	   shows the tree of the mismatching element

   OUTPUT
       If a mismatch is reported, a report is generated displaying the subpart of the tree that could not be matched. This will look like this:

       REASON: no_matching_node: annotation
	 no_matching_node: feature_set
	   no_matching_node: feature_span
	     no_matching_node: evidence
	       no_matching_node: evidence-id
		 data_mismatch(:15077290 ne :15077291): evidence-id AND evidence-id

       Due to the nature of tree matching, it can be difficult to specify exactly how trees do not match. To investigate this, you may need to use
       the -r and -v options. For the above output, I would recommend using

	 stag-diff -r feature_span -v

   ALGORITHM
       Both trees are recursively traversed... see the actual code for how this works

       The order of elements is not important; eg

	 <foo>
	   <bar>
	     <baz>1</baz>
	   </bar>
	   <bar>
	     <baz>2</baz>
	   </bar>
	 </foo>

       matches

	 <foo>
	   <bar>
	     <baz>2</baz>
	   </bar>
	   <bar>
	     <baz>1</baz>
	   </bar>
	 </foo>

       The recursive nature of this algorithm means that certain tree comparisons will explode wrt time and memory. I think this will only happen
       with very deep trees where nodes high up in the tree can only be differentiated by nodes low down in the tree.

       Both trees are loaded into memory to begin with, so it may thrash with very large documents

   AUTHOR
       Chris Mungall cjm at fruitfly dot org

SEE ALSO

       Data::Stag

perl v5.10.0							    2008-12-23							     STAG-DIFF(1p)
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