Author: lwall
Date: 2009-10-28 18:47:05 +0100 (Wed, 28 Oct 2009)
New Revision: 28938
Modified:
docs/Perl6/Spec/S05-regex.pod
Log:
[S05] decouple $() from .ast so we can use .ast as boolean
Modified: docs/Perl6/Spec/S05-regex.pod
===================================================================
--- docs/Perl6/Spec/S05-regex.pod 2009-10-28 17:42:52 UTC (rev 28937)
+++ docs/Perl6/Spec/S05-regex.pod 2009-10-28 17:47:05 UTC (rev 28938)
@@ -16,8 +16,8 @@
Created: 24 Jun 2002
- Last Modified: 26 Oct 2009
- Version: 104
+ Last Modified: 28 Oct 2009
+ Version: 105
This document summarizes Apocalypse 5, which is about the new regex
syntax. We now try to call them I<regex> rather than "regular
@@ -2430,9 +2430,9 @@
However, sometimes you would like an alternate scalar value to
ride along with the match. The C<Match> object itself describes
a concrete parse tree, so this extra value is called an I<abstract>
-object; it rides along as an attribute of the C<Match> object. C<$()>
-is a shorthand for C<$($/.ast)>. The C<.ast> method by default just
-returns the string between the C<$/.from> and C<$/.to> positions.
+object; it rides along as an attribute of the C<Match> object.
+The C<.ast> method by default returns an undefined value.
+C<$()> is a shorthand for C<$($/.ast // ~$/)>.
Therefore C<$()> is usually just the entire match string, but
you can override that by calling C<make> inside a regex:
@@ -2443,19 +2443,21 @@
# match succeeds -- ignore the rest of the regex
});
-This puts the new abstract node into C<$/.ast>. If the abstract object is
-returned that way, it may be of any type, not just a string.
+This puts the new abstract node into C<$/.ast>. An AST node
+may be of any type.
This makes it convenient to build up an abstract syntax tree of
arbitrary node types.
-You may also capture a subset of the match as the abstract object using
-the C<< <(...)> >> construct:
+=item *
+You may also capture a subset of the match using the C<< <(...)> >> construct:
+
"foo123bar" ~~ / foo <( \d+ )> bar /
say $(); # says 123
-In this case the abstract object is always a string when doing string
+In this case C<$()> is always a string when doing string
matching, and a list of one or more elements when doing list matching.
+This construct does not set the C<.ast> attribute.
=item *
