On Sat, Jun 28, 2003 at 03:51:49PM +0200, Kevin Pfeiffer wrote: > In article <[EMAIL PROTECTED]>, John W. Krahn wrote: > [...] > > Perhaps this article may help you understand. > > > > http://perl.plover.com/FAQs/Namespaces.html > > I've read this before (but it pays to reread it) and this time I also read the > "Seven Useful Uses of local". One thing MJD demonstrates is a clever wayt that one > can write one's one "map" and "grep"-like methods/functions. Only problem is that I > can't get it to work. > > I get the error: > Use of uninitialized value in concatenation (.) or string at ./sub_print_hash line > 20. > Can't call method "printhash" without a package or object reference at > ./sub_print_hash line 20. > > Here is my code: > > #!/usr/bin/perl > use warnings; > use strict; > > # sub_print_hash > > # from MJD's "Seven Useful Uses of local" - http://perl.plover.com/local.html > # very useful technique for building your own grep and map-like functions! > > > my %capitals = ( > Athens => "Greece", > Moscow => "Russia", > Helsinki => "Finland", > ); > foreach (keys %capitals) { > print "$_ => $capitals{$_}\n"; > } > > printhash { "$a," } %capitals; > > #printhash { "$a => $b\n" } %capitals; > > sub printhash (&\%) { > > my $code = shift; > my $hash = shift; > local ($a, $b); > > while (($a, $b) = each %$hash) { > print &$code(); > } > }
The only problem is that you have used printhash before declaring it, and in this case the declaration is important. -- Paul Johnson - [EMAIL PROTECTED] http://www.pjcj.net -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
