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Postings from April 2001
barries <barries@slaysys.com> wrote
> `isa' is also exportable and can be called as a sub with two argu-
> ments. This allows the ability to check what a reference points to.
> Example
>
> use UNIVERSAL qw(isa);
>
> if(isa($ref, 'ARRAY')) {
> #...
> }
Oh rats. That should have been mended when this was added to UNIVERSAL.pm
back in perl5.004_01:
These subroutines should not be imported via
"use UNIVERSAL qw(...)". If you want simple local access to
them you can do
*isa = \&UNIVERSAL::isa;
to import isa into your package.
So the attached patch should be applied to perl5.004_01.
(Actually, it works nicely on bleadperl as well. :-)
Mike Guy
--- ./pod/perlobj.pod.orig Thu Apr 26 14:11:24 2001
+++ ./pod/perlobj.pod Thu Apr 26 14:17:11 2001
@@ -361,12 +361,12 @@
C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS>
-C<isa> is also exportable and can be called as a sub with two arguments. This
-allows the ability to check what a reference points to. Example
+You can also call C<UNIVERSAL::isa> as a sub with two arguments. The
+first does not need to be an object or even a reference. This
+allows the ability to check what a reference points to, or whether
+something is a reference of a given type. Example
- use UNIVERSAL qw(isa);
-
- if(isa($ref, 'ARRAY')) {
+ if(UNIVERSAL::isa($ref, 'ARRAY')) {
#...
}
@@ -397,8 +397,7 @@
You may add other methods to the UNIVERSAL class via Perl or XS code.
You do not need to C<use UNIVERSAL> to make these methods
-available to your program. This is necessary only if you wish to
-have C<isa> available as a plain subroutine in the current package.
+available to your program (and you should not do so).
=head2 Destructors
End of patch
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