On Sep 21, Errin Larsen said:
>On Tue, 21 Sep 2004 14:58:43 -0400 (EDT), Jeff 'japhy' Pinyan
><[EMAIL PROTECTED]> wrote:
>> On Sep 21, Bob Showalter said:
>>
>> > my %hash = (
>> > foo => 1,
>> > bar => 2,
>> > baz => 3,
>> > qux => 4,
>> > );
>> >
>> >I would like to remove all the entries in the hash except for 'bar' and
>> >'qux'. (Actual hash has other entries which can vary at runtime. I know that
>> >I only want to keep 'bar' and 'qux' however).
>>
>> > my @keys = qw(bar qux);
>>
>> my %keep_these_keys;
>> @keep_these_keys{qw( bar qux )} = ();
>>
>> delete @hash{ grep !exists $keep_these_keys{$_}, keys %hash };
>
>So ... is there a way to return a 'not' slice of hashes? What I mean
>is, the 'keys' function returns a list of all keys in a slice. Is
>there a function to return a list of all keys in slice EXCEPT those
>keys that I explicitely pass? like this, maybe:
>
>my %my_hash = (
> foo => 1,
> bar => 2,
> baz => 3,
> qux => 4,
>);
>
>my @other_keys = not_keys( %my_hash, "foo", "bar" )
>
>and then @other_keys = qw( baz qux )
Write your own function. This is where prototypes come in handy:
# declare the function BEFORE you use it
# we could also define it here, but that might look ugly
sub not_keys (\%@);
# ...
my @other_keys = not_keys(%my_hash, "foo", "bar");
# ...
sub not_keys (\%@) {
my $hash = shift;
my %exclude;
@[EMAIL PROTECTED] = (); # build hash of keys to exclude
return grep !exists $exclude{$_}, keys %$hash;
}
--
Jeff "japhy" Pinyan % How can we ever be the sold short or
RPI Acacia Brother #734 % the cheated, we who for every service
http://japhy.perlmonk.org/ % have long ago been overpaid?
http://www.perlmonks.org/ % -- Meister Eckhart
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>
