John Deighan wrote:
At 02:20 PM 7/24/2005, Ed Chester wrote:


>>John Deighan::
>>
Is there a safe way to compare 2 floating point numbers in Perl? [snip]
My debugger says that they're both '630.24' [snip]
However, the == test fails and the != test succeeds
>>
>>can you post code with the comparison == that fails ?
>>if the debugger says they're the same, they're very very probably the same.
>>are you sure the variable (or whatever) you're giving to == are
>>really what you
>>want them to be?
>>there are lots of ways to compare numbers, right down to looping over the bits
>>and logically
>>XNRing them.

Sorry about the lack of sample code, but I know that people who work
with floating point numbers know about this problem, and I was
wondering what the best solution was. Here is sample code with
output. Note that I'm not formatting the output or rounding or
anything - just printing out the contents of the 2 variables.

my $sum1 = -237.15;
my $sum2;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;
$sum2 += -26.35;

print("sum1 = $sum1\n");
print("sum2 = $sum2\n");
if ($sum1 == $sum2) {

You could try something like:

if (abs ($sum1 - $sum2) < .0001) {

print("EQUAL\n");
}
else {
print("NT EQUAL\n");
}

UTPUT:

sum1 = -237.15
sum2 = -237.15
NT EQUAL

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Ken Barker graced perl with these words of wisdom:

What kind of post is this?

It was an informative help post, made especially informative and helpful
by the fact that the relevant material was included at the relevant point
in the code, as opposed to being top-posted.

I do not see that anything was added at all.

Then either your reading comprehension skills must not be so good, or
you're so self-righteous about top-posting that you can't be bothered to
look for the material of posters who insert material where it belongs. I
can only wonder what sort of code this causes you to produce. :-)

Give us all a break -
don't bother - whatever your intentions.

I'm certain that in future, $Bill won't bother responding to your pleas
for help!

At 06:35 PM 7/24/2005, $Bill Luebkert wrote:
>>John Deighan wrote:

Note that my quote accounts for one sign. This means that anything
$Bill wrote will have two signs in front of it. If you scroll down,
you'll see

[much snippage]

>my $sum1 = -237.15;
>my $sum2;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>$sum2 += -26.35;
>>
>print("sum1 = $sum1\n");
>print("sum2 = $sum2\n");
>if ($sum1 == $sum2) {
>>
>>You could try something like:
>>
>if (abs ($sum1 - $sum2) < .0001) {

Hmmm The four lines above all have two signs in front of them. They
must have been written by $Bill!

>>

>,-/- __ _ _ $Bill Luebkert
>Mailto:dbecoll (AT) adelphia (DOT) net
>(_/ / ) // // DBE Collectibles Mailto:dbe (AT) todbe (DOT) com
>/ ) /--< o // // Castle of Medieval Myth & Magic
>http://www.todbe.com/
/-' //_<_</_</_ http://dbecoll.tripod.com/ (My Perl/Lakers
>>stuff)
>>Perl-Win32-Users mailing list
>>Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
>>To unsubscribe:

Note that these lines form $Bill's signature, and also have two signs in
front of them.

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And as a service to everybody, note that these lines are appended by the
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