Author: larry
Date: Mon Oct 9 00:22:24 2006
New Revision: 12875
Modified:
doc/trunk/design/syn/S05.pod
Log:
P5's s[pat][repl] syntax is dead, now use s[pat] = "repl"
Modified: doc/trunk/design/syn/S05.pod
==============================================================================
--- doc/trunk/design/syn/S05.pod (original)
+++ doc/trunk/design/syn/S05.pod Mon Oct 9 00:22:24 2006
@@ -14,9 +14,9 @@
Maintainer: Patrick Michaud <[EMAIL PROTECTED]> and
Larry Wall <[EMAIL PROTECTED]>
Date: 24 Jun 2002
- Last Modified: 4 Oct 2006
+ Last Modified: 8 Oct 2006
Number: 5
- Version: 35
+ Version: 36
This document summarizes Apocalypse 5, which is about the new regex
syntax. We now try to call them I<regex> rather than "regular
@@ -88,10 +88,18 @@
s/pattern/{ doit() }/
+or:
+
+ s[pattern] = doit()
+
Instead of C</ee> say:
s/pattern/{ eval doit() }/
+or:
+
+ s[pattern] = eval doit()
+
=item *
Modifiers are now placed as adverbs at the I<start> of a match/substitution:
@@ -2876,15 +2884,71 @@
the longest one wins. In the case of two identical sequences the
first in order wins.
+=back
+
+=head1 Substitution
+
There are also method forms of C<m//> and C<s///>:
- $str.match(//);
- $str.subst(//, "replacement");
- $str.subst(//, {"replacement"});
- $str.=subst(//, "replacement");
- $str.=subst(//, {"replacement"});
+ $str.match(/pat/);
+ $str.subst(/pat/, "replacement");
+ $str.subst(/pat/, {"replacement"});
+ $str.=subst(/pat/, "replacement");
+ $str.=subst(/pat/, {"replacement"});
-=back
+There is no syntactic sugar here, so in order to get deferred
+evaluation of the replacement you must put it into a closure. The
+syntactic sugar is provided only by the quotelike forms. First there
+is the standard "triple quote" form:
+
+ s/pattern/replacement/
+
+Only non-bracket characters may be used for the "triple quote". The
+right side is always evaluated as if it were a double-quoted string
+regardless of the quote chosen.
+
+As with Perl 5, a bracketing form is also supported, but unlike Perl 5,
+Perl 6 uses the brackets I<only> around the pattern. The replacement
+is then specified as if it were an ordinary item assignment, with ordinary
+quoting rules. To pick your own quotes on the right just use one of the C<q>
+forms. The substitution above is equivalent to:
+
+ s[pattern] = "replacement"
+
+or
+
+ s[pattern] = qq[replacement]
+
+This is not a normal assigment, since the right side is evaluated each
+time the substitution matches (much like the pseudo-assignment to declarators
+can happen at strange times). It is therefore treated as a "thunk", that is,
+as if it has implicit curlies around it. In fact, it makes no sense at
+all to say
+
+ s[pattern] = { doit }
+
+because that would try to substitute a closure into the string.
+
+Any scalar assignment operator may be used; the substitution macro
+knows how to turn
+
+ $target ~~ s:g [pattern] op= expr
+
+into something like:
+
+ $target.subst(rx:g [pattern], { $() op expr })
+
+So, for example, you can multiply every dollar amount by 2 with:
+
+ s:g [\$ <( \d+ )>] *= 2
+
+(Of course, the optimizer is free to do something faster than an actual
+method call.)
+
+You'll note from the last example that substitutions only happen on
+the "official" string result of the match, that is, the C<$()> value.
+(Here we captured C<$()> using the C<< <(...)> >> pair; otherwise we
+would have had to use lookbehind to match the C<$>.)
=head1 Positional matching, fixed width types
