Author: lwall
Date: 2010-08-16 19:49:53 +0200 (Mon, 16 Aug 2010)
New Revision: 32013
Modified:
docs/Perl6/Spec/S02-bits.pod
Log:
[S02] spec which methods Nil responds to,
and that it propagates Nil on unrecognized methods
Modified: docs/Perl6/Spec/S02-bits.pod
===================================================================
--- docs/Perl6/Spec/S02-bits.pod 2010-08-16 14:30:39 UTC (rev 32012)
+++ docs/Perl6/Spec/S02-bits.pod 2010-08-16 17:49:53 UTC (rev 32013)
@@ -14,7 +14,7 @@
Created: 10 Aug 2004
Last Modified: 16 Aug 2010
- Version: 221
+ Version: 222
This document summarizes Apocalypse 2, which covers small-scale
lexical items and typological issues. (These Synopses also contain
@@ -2153,14 +2153,23 @@
you can think of Perl 5 references as a degenerate form of C<Capture>
when you want to refer only to a single item.
-There is a special C<Parcel> value named C<Nil>. It means "there is no
-value here". It is the undefined equivalent of the empty C<()> list, except
that the
-latter is defined and means "there are 0 arguments here". The C<Nil> value
returns
-itself if you iterate it or try to get a positional value from it, but
+There is a special C<Parcel> value named C<Nil>. It means "there
+is no value here". It is the undefined equivalent of the empty
+C<()> list, except that the latter is defined and means "there are
+0 arguments here". The C<Nil> value returns itself if you iterate
+it or try to get a positional value from it via subscripting, but
interpolates as a null list into flat context, and an empty C<Seq>
-into slice context. Since method calls are performed directly on
-any object, C<Nil.defined> returns C<False> while C<().defined> returns
C<True>.
+into slice context. In either case, a warning is issued.
+Since method calls are performed directly on any object, C<Nil>
+can respond to certain method calls. C<Nil.defined> returns
+C<False> (whereas C<().defined> returns C<True>). C<Nil.so> also
+returns C<False>. C<Nil.ACCEPTS> is always false. C<Nil.perl> and
+C<Nil.Str> return C<"Nil">. C<Nil.Stringy> returns '' with a warning.
+C<Nil.Numeric> returns 0 with a warning. Any undefined method call
+on C<Nil> returns C<Nil>, so that C<Nil> propagates down method
+call chains.
+
Assigning C<Nil> to any scalar container causes the
container to throw out any contents and restore itself to an
uninitialized state (after which it will contain a type object
