Author: larry
Date: Sat Jun 21 17:43:15 2008
New Revision: 14555
Modified:
doc/trunk/design/syn/S05.pod
Log:
clarifications requested by cognominal++
Modified: doc/trunk/design/syn/S05.pod
==============================================================================
--- doc/trunk/design/syn/S05.pod (original)
+++ doc/trunk/design/syn/S05.pod Sat Jun 21 17:43:15 2008
@@ -14,9 +14,9 @@
Maintainer: Patrick Michaud <[EMAIL PROTECTED]> and
Larry Wall <[EMAIL PROTECTED]>
Date: 24 Jun 2002
- Last Modified: 11 Jun 2008
+ Last Modified: 21 Jun 2008
Number: 5
- Version: 81
+ Version: 82
This document summarizes Apocalypse 5, which is about the new regex
syntax. We now try to call them I<regex> rather than "regular
@@ -391,7 +391,7 @@
is equivalent to the Perl 6 syntax:
- m/ :i ^^ [ <[a..z]> || \d ] ** 1..2 <before \s> /
+ m/ :i ^^ [ <[a..z]> || \d ] ** 1..2 <?before \s> /
=item *
@@ -1399,6 +1399,11 @@
# short for <?{ .pos === $pos }>
# (considered declarative until $pos changes)
+It is legal to use any of these assertions as named captures by omitting the
+punctuation at the front. However, capture entails some overhead in both
+memory and computation, so in general you want to suppress that for data
+you aren't interested in preserving.
+
The C<after> assertion implements lookbehind by reversing the syntax
tree and looking for things in the opposite order going to the left.
It is illegal to do lookbehind on a pattern that cannot be reversed.
@@ -1534,7 +1539,7 @@
is equivalent to:
- / <after foo> \d+ <before bar> /
+ / <?after foo> \d+ <?before bar> /
except that the scan for "C<foo>" can be done in the forward direction,
while a lookbehind assertion would presumably scan for C<\d+> and then
@@ -3426,7 +3431,7 @@
Subcaptures are returned as a multidimensional list, which the user can
choose to process in either of two ways. If you refer to
C<@()>, the multidimensionality is ignored and all the matches are returned
-flattened (but still lazily). If you refer to @@(), you can
+flattened (but still lazily). If you refer to C<@@()>, you can
get each individual sublist as a Capture object. (That is, there is a C<@@()>
coercion operator that happens, like C<@()>, to default to C<$/>.)
As with any multidimensional list, each sublist can be lazy separately.
@@ -3583,6 +3588,13 @@
=back
+=item *
+
+To switch to a different grammar in the middle of a regex, you may use the
C<:lang> adverb.
+For example, to match an expression <expr> from $funnylang that is embedded in
curlies, say:
+
+ token funnylang { '{' [ :lang($funnylang.unbalanced('}')) <expr> ] '}' }
+
=head1 Syntactic categories
For writing your own backslash and assertion subrules or macros, you may
