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Re: Re: Re: Hash slices ?

by davorg (Chancellor)
on Dec 01, 2000 at 17:53 UTC ( #44343=note: print w/ replies, xml ) Need Help??

in reply to Re: Re: Hash slices ?
in thread Hash slices ?

Any one further investigation, it seems that my original solution suffered from a fundamental problem.

my %hash = (one => 1, two => 2, three => 3); my @keys = qw(four five six); my @slice = @hash{@keys};

@slice is now contains four undef elements, where I thought it would be an empty list (don't know why I thought that - it was very early in the morning.

If the hash slice was interpreted as an array, it would therefore always be true and therefore doesn't solve ChOas' original problem. That would be better addressed using something like:

if (grep { exists %hash{$_} } @keys) { print "yep\n"; } else { print "nope\n"; }

"Perl makes the fun jobs fun
and the boring jobs bearable" - me

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Re: Re: Re: Re: Hash slices ?
by snax (Friar) on Dec 01, 2000 at 18:03 UTC
    perl -w -e '%x=(a=>7,b=>8,c=>9);@s=(qq(a),qq(b));$y=@x{@s};print $y;'
    returns 8 -- so it is pretty clearly the case that a hash slice is properly a list.

Re: Re: Re: Re: Hash slices ?
by ChOas (Curate) on Dec 01, 2000 at 18:09 UTC
    I was thinking about doing it like this to avoid the grep:
    sub Match{foreach (@keys) {return 1 if exists $hash{$_};}return 0} if ( Match ) { print "yep\n"; } else { print "nope\n"; };
    But I was thinking about that already before I thought of
    the slice ;))

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