Hash-slicing question...

dragonchild has asked for the wisdom of the Perl Monks concerning the following question:

I've got a hashref containing keys A through D. I want to pass the values of A and B to a given function like so:

my $returnValue = functionCall({
    A => $hashRef->{A},
    B => $hashRef->{B},

    Foo => 'Bar',
});
[download]

Now, I know I could just pass it the whole hashref by dereferencing it within the anonymous hashref, but I don't want to do that. (That could also clobber default values that functionCall() would give me.) What I'd love to do is tell the interpreter to create me a set of keys and values from $hashRef with the keys I give it.

Any ideas?

------
/me wants to be the brightest bulb in the chandelier!

Vote paco for President!

Comment on Hash-slicing question... Download Code

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Re: Hash-slicing question... by ozone (Friar) on Aug 28, 2001 at 00:34 UTC
try using 'map': `my $rv = fc({ map { $_ => $hashRef->{$_} } ('A', 'B', ) }); .....` [download]	[reply] [d/l]
Re: Hash-slicing question... by clintp (Curate) on Aug 28, 2001 at 06:25 UTC
I like ozone's answer because you're not actually asking for a slice of the hash. You want the values and the keys to pass to your function. So you actually want a subset of the original hash. Use map(). If you just wanted values, you could say: `@{$hashRef}{qw(A B C D)}` [download] and that's an honest slice.	[reply] [d/l]
Re: Hash-slicing question... by DBX (Pilgrim) on Aug 29, 2001 at 09:34 UTC
Another solution is to change how your function call handles defaults. Depending on how you set it up, they won't get clobbered: `sub functionCall{ my ($hashref) = @_; my %defaults = ( A => 1, D => 4, ); %$hashref = ( %$hashref, %defaults, ); }` [download] You can change this to true defaults if you switch the order to: `%$hashref = ( %defaults, %$hashref, );` [download]	[reply] [d/l] [select]
Re: Re: Hash-slicing question... by dragonchild (Archbishop) on Aug 29, 2001 at 16:21 UTC
That would definitely be a thought, but the functions I'm using are from a set of libraries whose behavior I can't change. shrugs ------ /me wants to be the brightest bulb in the chandelier! Vote paco for President!	[reply]