in reply to Re: problem with variables
in thread problem with variables

No, eq is for string comparison, which definitely wouldn't work here. In Perl == does numeric comparison.

See perlop.

You may be thinking of (korn) shell where it's the other way round.

s^^unp(;75N=&9I<V@`ack(u,^;s|\(.+\`|"$`$'\"$&\"\)"|ee;/m.+h/&&print$&

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Re^3: problem with variables
by JohnMG (Beadle) on Oct 19, 2005 at 17:19 UTC
    Works fine for me:
    #!/usr/bin/perl

use strict;
use warnings;

my $num1 = 1234.56789;
my $num2 = 1234.56789111;

if ( $num1  ==  $num2 ) {
    print "equal.\n";
}
else {
    print "Please don't try to check for equality of floats that way.\
+n";
}

if ( sprintf( "%.3f", $num1 ) == sprintf( "%.3f", $num2 ) ) {
    print "Yup, they show up as equal.\n";
}

if ( sprintf( "%.3f", $num1 ) eq sprintf( "%.3f", $num2 ) ) {
    print "Yup. This works too.\n";
}

    [download]
    output:
    Please don't try to check for equality of floats that way.
Yup, they show up as equal.
Yup. This works too.

    [download]
[reply]
[d/l]
[select]
      Actually, now that brain is in gear, I think you *always* want to use eq rather than == for comparing floats. If you use 
      sprintf( "%.3f", $num1 ) == sprintf( "%.3f", $num2 )

      [download]
      that just puts you right back to where you started: comparing floats with ==.
[reply]
[d/l]
        Yes, but if the strings are eq, the floats that come from those strings will be ==. It's a deterministic thing. That said, it makes more sense to compare them with eq, since the output of sprintf is a string. Why force the conversion back?
        Caution: Contents may have been coded under pressure.
[reply]

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