[SOLVED] Simple Operation get wrong result

[kitnos]

info:

PHP Version 5.1.6

 

Why do i get this value in a simple operation?

 

<?php

echo (1.2 - 0.1) - 1.1;

?>

 

result = -2.2204460492503E-016

[kenrbnsn]

That the result of converting floating point numbers in and out of binary. It's not exact and never will be. For all practical purposes, the result you got is zero. If you round it to one decimal place you will see that.

 

Ken

 

 

[neel_basu]

Ya Its Strange

<?php
header('Content-Type: text/plain');
$res1 = (1.2-0.1)-1.1;// = 1.1-1.1 -> Evaluates to Zero
$res2 = (2.2-0.1)-2.1;// = 2.1-2.1 -> Also Evaluates to Zero
echo $res1."\t".gettype($res1);
echo "\n";
echo $res2."\t".gettype($res2);
?>

-2.22044604925E-016 double

0 double

[kitnos]

I need to have precision on this function and when this happens the result goes crazy  :-\

[kenrbnsn]

How many digits of precision do you need?

 

Ken

[paul2463]

echo number_format(((1.2 - 0.1) - 1.1), 0);

//outputs -0

echo number_format(((1.2 - 0.1) - 1.1), 1);

//outputs -0.0

echo number_format(((1.2 - 0.1) - 1.1), 2);

//outputs -0.00

[per1os]

A work around is to do maybe try this:

 

<?php
header('Content-Type: text/plain');
$res1 = (1.2-0.1)-1.1;// = 1.1-1.1 -> Evaluates to Zero
$res2 = (2.2-0.1)-2.1;// = 2.1-2.1 -> Also Evaluates to Zero
echo convertNumber($res1)."\t".gettype($res1);
echo "\n";
echo convertNumber($res2)."\t".gettype($res2);

function convertNumber($num) {
if (number_format($num,1) == -0.0) {
	return 0;
}

        return $num;
}

 

I would create my own function, like above. And just make sure you use it on all number values being calculated. This will return the correct results you want.

[kitnos]

Thanks All . Problem solved

This forum is very quick and with good people

 

Im making some gadgets to a physics software and this was bugging me