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Postings from September 2000
On Wed, 6 Sep 2000 22:58:05 -0400, John Porter wrote:
> keys %hash = @things;
>
>is defined as being equivalent to
>
> @hash{ @things } = ();
>
>This is to support hash-based set operations in a more
>natural way, i.e.
>
> keys %hash = grep { exists $a{$_} } keys %b;
I have doubts if this would indeed make life simpler. It's a shortcut
for something that is already quite simple, but doing nothing for
slightly more complex situations. In short:
@hash{@keys} = ();
is the simple case. It can work even if @keysis not an array, but a
list instead (a grep() expression, for example). These are more complex
but related things:
@hash{@keys) = 0 .. $#keys;
Try *that* with a list.
Or, coming back to your example: fill a new hash with key/value pairs of
%b with only where intries in %a exist:
@hash{grep { exists $a{$_} } keys %b} =
@b{grep { exists $a{$_} } keys %b};
Ugh.
If you can find a simple alternative syntax for these two, then you have
my blessing.
--
Bart.
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