Author: larry
Date: Fri Nov 7 10:10:52 2008
New Revision: 14602
Modified:
doc/trunk/design/syn/S02.pod
Log:
recast $?FOO matching in terms of new pair matching syntax
Modified: doc/trunk/design/syn/S02.pod
==============================================================================
--- doc/trunk/design/syn/S02.pod (original)
+++ doc/trunk/design/syn/S02.pod Fri Nov 7 10:10:52 2008
@@ -14,7 +14,7 @@
Date: 10 Aug 2004
Last Modified: 7 Nov 2008
Number: 2
- Version: 141
+ Version: 142
This document summarizes Apocalypse 2, which covers small-scale
lexical items and typological issues. (These Synopses also contain
@@ -1981,9 +1981,7 @@
All the nested C<@?> variables are ordered from the innermost to the
outermost, so C<@?BLOCK[0]> is always the same as C<&?BLOCK>.
-The following return objects that contain all pertinent info; in
-particular they may be smartmatched against strings for the name and
-against version literals for the version:
+The following return objects that contain all pertinent info:
$?OS Which operating system am I compiled for?
$?DISTRO Which OS distribution am I compiling under
@@ -2001,6 +1999,20 @@
$?GRAMMAR Which grammar am I in?
@?GRAMMAR Which nested grammars am I in?
+It is relatively easy to smartmatch these constant objects
+against pairs to check various attributes such as name,
+version, or authority:
+
+ given $?VM {
+ when :name<Parrot> :ver(v2) { ... }
+ when :name<CLOS> { ... }
+ when :name<SpiderMonkey> { ... }
+ when :name<JVM> :ver(v6.*) { ... }
+ }
+
+Matches of constant pairs on constant objects may all be resolved at
+compile time, so dead code can be eliminated by the optimizer.
+
Note that some of these things have parallels in the C<*> space at run time:
$*OS Which OS I'm running under
