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Add support for named sub-expressions.

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[SVN r52823]
This commit is contained in:
John Maddock
2009-05-07 09:46:51 +00:00
parent 30941e330d
commit 55d979060c
49 changed files with 1287 additions and 206 deletions
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19
doc/syntax_perl.qbk
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@ -185,8 +185,12 @@ You can also use the \g escape for the same function, for example:
parsing of the expression in cases like =\g{1}2= or for indexes higher than 9 as in =\g{1234}=]]
[[=\g-1=][Match whatever matched the last opened sub-expression]]
[[=\g{-2}=][Match whatever matched the last but one opened sub-expression]]
[[=\g{one}=][Match whatever matched the sub-expression named "one"]]
]
Finally the \k escape can be used to refer to named subexpressions, for example [^\k<two>] will match
whatever matched the subexpression named "two".
[h4 Alternation]
The =|= operator will match either of its arguments, so for example:
@ -425,6 +429,21 @@ Any other escape sequence matches the character that is escaped, for example
Perl-specific extensions to the regular expression syntax all start with =(?=.
[h5 Named Subexpressions]
You can create a named subexpression using:
(?<NAME>expression)
Which can be then be refered to by the name /NAME/. Alternatively you can delimit the name
using 'NAME' as in:
(?'NAME'expression)
These named subexpressions can be refered to in a backreference using either [^\g{NAME}] or [^\k<NAME>]
and can also be refered to by name in a [perl_format] format string for search and replace operations, or in the
[match_results] member functions.
[h5 Comments]
=(?# ... )= is treated as a comment, it's contents are ignored.