in reply to check if 2 values are equal

The following code may do what you want:

use strict;
use warnings;

my @pairs =
    (
    [undef, undef], [0, undef], [0, 0], ['', undef], ['', ''], [1, und
+ef], [1, 1],
    [0, '0'], [0, 0], ['0', '0'], ['0e0', '0'], ['x', '0'], ['x', 0],
    );

 
for (@pairs)
    {
    my @pair = (@$_);
    print defined $pair[0] ? ">$pair[0]<" : 'undef';
    print ', ' . (defined $pair[1] ? ">$pair[1]<" : 'undef');
    print ': ' . (equals (@$_) ? "match\n" : "different\n");
    }

sub equals {
    my ($lhs, $rhs) = @_;
    
    #False if mix of defined and undef
    return 0 if defined $lhs != defined $rhs;
    
    # True if both undef
    return 1 if ! defined $lhs && ! defined $rhs;
    
    # False if different as numbers
    no warnings "numeric";
    return 0 if (0 + $lhs) != (0 + $rhs);
    
    # False if different as strings
    return 0 if ('' . $lhs) ne ('' . $rhs);
    
    return 1;
}

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Prints:

undef, undef: match
>0<, undef: different
>0<, >0<: match
><, undef: different
><, ><: match
>1<, undef: different
>1<, >1<: match
>0<, >0<: match
>0<, >0<: match
>0<, >0<: match
>0e0<, >0<: different
>x<, >0<: different
>x<, >0<: different

[download]
DWIM is Perl's answer to Gödel

Replies are listed 'Best First'.
Re^2: check if 2 values are equal
by eXile (Priest) on Jan 24, 2006 at 21:18 UTC
    thanks very much, this does what i'd like it to do, and if i compare it to my orginal function it even takes care of the 'numeric 0' vs. 'empty string' inequality. 
    my @vals =        (undef,           0,        '0', 'aap', 1, 't','');
my @expl =        ('undef','numeric 0','string 0', 'string "aap"', 'nu
+mber 1', 'string t','empty string');

my ($i,$j);

for ($i=0; $i <= scalar(@vals-1); $i++) {
    for ($j=0; $j <= scalar(@vals-1); $j++) {
        # equals 1
        print "equals_org '$expl[$i]'\t'$expl[$j]'\t" . equals_org($va
+ls[$i],$vals[$j]) . "\n";
        print "equals_new '$expl[$i]'\t'$expl[$j]'\t" . equals_new($va
+ls[$i],$vals[$j]) . "\n";
        print "--\n";
    }
}

sub equals_org {
    my ($val1, $val2) = @_;

    # first test for undef-ness
    if ( ! defined $val1 || ! defined $val2 ) {
        return 1 if (! defined $val1 && ! defined $val2 );
        return undef; #case one is undef, other is def
    }
    # have to do next line this because strings evaluate to 0 in == co
+ntext ...
    if ( ! $val1  && ! $val2 ) {
        # then test for ""-ness
        return 1 if ( ($val1 eq "") && ($val2 eq "") );
        return undef if ( $val1 eq "" || $val1 eq "" );  
        #case one is "" other is 0
        # then test for 0-ness 
        return 1 if ( ($val1 == 0) && ($val2 == 0) );
    }
    # then test for equality using 'eq'
    return 1 if ( $val1 eq $val2 );
    # then test for equality using '=='
    if ( int($val1) && int($val2) ) {
        # all other number cases are already covered by
        # above tests (eg. both 0, or both the same string)
        # this merely takes care of cases like:
        #   1000.0000 == 1000
        return 1 if ( $val1 == $val2 );
    }
    # couldn't find any, so i guess they are not equal
    return undef;
}

sub equals_new {
    my ($lhs, $rhs) = @_;
    
    #False if mix of defined and undef
    return 0 if defined $lhs != defined $rhs;
    
    # True if both undef
    return 1 if ! defined $lhs && ! defined $rhs;
    
    # False if different as numbers
    no warnings "numeric";
    return 0 if (0 + $lhs) != (0 + $rhs);
    
    # False if different as strings
    return 0 if ('' . $lhs) ne ('' . $rhs);
    
    return 1;
}

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[reply]
[d/l]
Re^2: check if 2 values are equal
by thedoe (Monk) on Jan 24, 2006 at 21:57 UTC

    I'm a bit confused. Shouldn't 

    >0e0<, >0<: different

    [download]
    be a match?

[reply]
[d/l]

      0e0 and 0 are different as a string and the same as a number. OP seems to like it evaluated as different. A solution involving looks_like_number is required to get the result you would like, else 'x' and 'y' would be a match (0 == 0).

      DWIM is Perl's answer to Gödel
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[d/l]
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