keys function question

[raflach]

if I have an object $obj that contains an element 'param' obtained by $obj->{'param'} that is a hash whose elements would be referenced by $obj->{'param'}{key}, and I want to iterate through the keys of this hash, i would try the following:

for my $key ( keys $obj->{'param'} ) {
    #do something with data
}

That doesn't work, so I tried enclosing the hash in the following ways  keys {$obj->{'param'}} and  keys ($obj->{'param'}) and  keys [$obj->{'param'}] and all give me the similar errors... either

Type of arg 1 to keys must be hash ( not hash elem) at ....
or
Type of arg 1 to keys must be hash (not scalar ref constructor) at ...
+.

I know I'm being stupid somehow... help

[tye]

keys %{$obj->{param}}

[cwest]

keys %{$obj->{param}}

Enjoy!

--
Casey

[tye]

Okay, so I left off the "Enjoy!" and so ctweten's has gotten more votes than mine. ;)

This discussion has been so short and to the point, I thought I'd add a bit...

I dislike having to use the %{...} syntax as it is hard to read. One solution is:

    $ref= $obj->{param};
    for(  keys %$ref  ) {
        Mung( $ref->{$_} );
    }

But what we really need is a post-fix operator that give you the whole hash (or array, or scalar, etc.) from a reference:

    my @keys= keys $obj->{param}->%;

This was proposed on perl5-porters a while back but noone has submitted a patch (as far as I know) to implement it. So here is your chance to become famous. Go to the perl5-porters archive and read up on the proposal and you've got a great project for learning Perl guts.

[cwest]

Oh C'mon, I voted you up, now you're winning :-)

I'll have a few spare tuits comming soon.

I'll have a look at this, sounds fun!

I've never hacked Perl guts before but I'm willing to give it a shot.

print foreach $r->%;
print foreach $r->@;
print foreach $r->$;
print foreach $r->*;

Enjoy! :-)

--
Casey

[japhy]

I disagree. Referencing and derefencing should be pre-fix, and if you don't like the SIGIL{} syntax, add whitespace. $foo->\ is silly-looking. \$foo is not. $foo->% also looks silly to me, and if %$foo is too noisy, do %{ $foo }.