John W. Krahn wrote: > Rob Dixon wrote: > > > > Well done Kevin! > > > > Just a couple of points. > > > > Kevin Pfeiffer wrote: > > > > > > (I noticed that, too.) But thanks to your tip I think I've > > > created my first recursive sub-routine (only tested on this > > > example). If it does what the OP requested (and y'all don't > > > find too much wrong > > > with it) then I'm a happy man! > > > > > > pad_keys($self); > > > print Dumper(\$self); > > > > > > sub pad_keys { > > > my $ref = shift; > > > if (ref $ref eq "HASH") { > > > for my $value (%$ref) { > > > > This will loop over all the keys and values in the > > hash, in the order key1, value1, key2, value2, ... > > All you want is the values. > > > > > if (ref $value eq "HASH") { > > > pad_keys($value); > > > } > > > } > > > for (keys %$ref) { > > > my $old = $_; > > > tr/ /_/; > > > $ref->{$_} = $ref->{$old}; > > > > You ought to check whether the new key already exists, otherwise > > you're going o be losing data. > > > > > delete $ref->{$old}; > > > } > > > } > > > } > > > > Finally, there's no need process the values and then the keys > > in separate loops. Each execution of either loop corresponds to > > a key/value pair so you can write > > > > foreach (keys) { > > modify key; > > recurse on value; > > } > > > > This is what I came up with. It skips the rest of the loop > > if the new key is the same as the old one, and uses the > > fact that 'delete' returns the value of the element it > > deleted. > > > > sub pad_keys { > > my $ref = shift; > > return unless ref $ref eq 'HASH'; > > foreach (keys %$ref) { > > pad_keys($ref->{$_}); > > next unless (my $new = $_) =~ tr/ /_/; > > if (exists $ref->{$new}) { > > warn "Padded key $new already exists"; > > } > > else { > > $ref->{$new} = delete $ref->{$_}; > > } > > } > > } > > Kevin and Rob, > > perldoc -q "add or remove keys from a hash" > > Found in /usr/lib/perl5/5.6.0/pod/perlfaq4.pod > What happens if I add or remove keys from a hash while > iterating over it? > > Don't do that. :-) > > [lwall] In Perl 4, you were not allowed to modify a hash > at all while iterating over it. In Perl 5 you can delete > from it, but you still can't add to it, because that might > cause a doubling of the hash table, in which half the > entries get copied up to the new top half of the table, at > which point you've totally bamboozled the iterator code. > Even if the table doesn't double, there's no telling > whether your new entry will be inserted before or after > the current iterator position. > > Either treasure up your changes and make them after the > iterator finishes, or use keys to fetch all the old keys > at once, and iterate over the list of keys.
As far as I knew this was only a problem with iterating using while (my ($k, $v) = each %hash) { : } if instead you do foreach (keys %hash) { : } it's the same as doing my @keys = keys %hash; foreach (@keys) { : } which would be fine here. I would write some code to check but it's not going to happen tonight! Cheers, Rob -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]