On 8 Sep 2000 04:57:46 -0000, Perl6 RFC Librarian wrote:
>Instead of
>
> %subhash = map { f($_) ? ($_, $hash{$_}) : () } keys %hash; # lengthy
>
>one may now write
>
> %subhash = %hash{f($_)}; # code block f($_) will be evaluated for Truth
>over all the keys
I almost liked that one.
I like what it produces: a hash slice that contains not only the values,
but the keys and the values, interleaved.
But I do not like the built-in grep.
I would prefer this syntax:
%extract = %hash{@keys};
which is like:
%extract = map { $_ => $hash{$_} } @keys;
It's more in sync with current perl:
@values = @hash{@keys};
which returns a list of (just the) hash values.
If you want the grep, you can use it explicitely:
%extract = %hash{ grep f($_), keys %hash };
--
Bart.
