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Re: check if 2 values are equal

by davido (Archbishop)
on Jan 24, 2006 at 23:37 UTC ( #525349=note: print w/ replies, xml ) Need Help??


in reply to check if 2 values are equal

Perl already knows how to do all the work for you. You can just use a hash in almost the same way you would assure uniqueness in a list.:

sub isequal { return 0 if ( grep{ !defined($_) } @_ ) != scalar @_; no warnings qw/uninitialized/; my %gadget; @gadget{ @_ } = (); return scalar keys %gadget == 1 ? 1 : 0; }

This works by creating a hash whos keys are the items being compared. If after creating the keys you have one element, you've got equality. If you have more than one element, you have inequality. The only tricky part is to be sure to silence the warning you get for making a hash key out of 'undef', and to deal with the fact that undef stringifies to ''.

Here is a test example:

use strict; use warnings; use diagnostics; sub isequal { return 0 if ( grep { ! defined( $_ ) } @_ ) != scalar @_; no warnings qw/uninitialized/; my %gadget; @gadget{ @_ } = (); return scalar keys %gadget == 1 ? 1 : 0; } my @test = ( [ 0, 1 ], [ "1", "one" ], [ 0, "0" ], [ 0, undef ], [ 1, undef ], [ "hello", undef ], [ undef, undef ], [ 1, 1 ], [ "1", 1 ], [ "hello", "hello" ] ); foreach my $items ( @test ) { my( $left, $right ) = @{ $items }; my $comp = isequal( $left, $right ); foreach( $left, $right ) { ! defined $_ and $_ = "undef"; } print "Testing $left, $right == ", $comp ? "equal\n" : "not equal\ +n"; }

Update: Another advantage to this method that may not be immediately apparent is that it can be used to test a list of any number of items.

Enjoy!


Dave


Comment on Re: check if 2 values are equal
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Re^2: check if 2 values are equal
by eXile (Priest) on Feb 07, 2006 at 01:34 UTC
    thanks, I eventually used your solution, with a minor modification:
    sub isequal { return 0 if ( grep { ! defined( $_ ) } @_ ) == scalar @_; no warnings qw/uninitialized/; my %gadget; @gadget{ @_ } = (); return scalar keys %gadget == 1 ? 1 : 0; }
    (changed the != into a == in the first line in the function)

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