Author: lwall
Date: 2010-02-24 19:26:58 +0100 (Wed, 24 Feb 2010)
New Revision: 29828
Modified:
docs/Perl6/Spec/S03-operators.pod
Log:
[S03] when and ~~ to warn on direct use of "True" or "False"
Modified: docs/Perl6/Spec/S03-operators.pod
===================================================================
--- docs/Perl6/Spec/S03-operators.pod 2010-02-24 18:11:54 UTC (rev 29827)
+++ docs/Perl6/Spec/S03-operators.pod 2010-02-24 18:26:58 UTC (rev 29828)
@@ -16,7 +16,7 @@
Created: 8 Mar 2004
Last Modified: 19 Feb 2010
- Version: 193
+ Version: 194
=head1 Overview
@@ -3464,6 +3464,8 @@
Any .[...] array value slice truth ?all(X) i.e. ?all(.[...])
Any .{...} hash value slice truth ?all(X) i.e. ?all(.{...})
Any .<...> hash value slice truth ?all(X) i.e. ?all(.<...>)
+ Any True ~~ True (parsewarn)
+ Any False ~~ False match (parsewarn)
Any Bool simple truth X
Any Numeric numeric equality +$_ == X
@@ -3680,8 +3682,18 @@
when .Bool == 0 {...}
}
-Better, just use an C<if> statement.
+Better, just use an C<if> statement. In any case, if you try to smartmatch
+with C<~~> or C<when>, it will recognize C<True> or C<False> syntactically
+and warn you that it won't do what you expect. The compiler is also allowed
+to warn about any other boolean construct that does not test C<$_>, to the
+extent it can detect that.
+In a similar vein, any function (such as C<grep>) that takes a
+C<Matcher> will not accept an argument of type C<Bool>, since that
+almost always indicates a programming error. (One may always use
+C<*> to match anything, if that's what you really want. Or use a closure
+that returns a constant boolean value.)
+
Note also that regex matching does I<not> return a C<Bool>, but merely
a C<Match> object that can be used as a boolean value. Use an explicit
C<?> or C<true> to force a C<Bool> value if desired.
