Brian P. O'Donnell wrote:
<?
$a = 252.73;
$b = 252.73;
$c = 0;
if ($a == ($b + $c))
{
// do the first thing
}
elseif ($a > ($b + $c))
{
// do the second thing
}
elseif ($a < ($b + $c))
{
// do the third thing
}
?>
Each of the three variables is derived by some earlier calculation, but for
testing purposes I have made sure that they end up being $a = $b and $c = 0.
I have tested for three different values (of $a) and gotten all three
results. That is, once the first block has executed, once the second block
and once the third block.
Am I missing something really obvious here?
This is an inherent problem with floating-point operations, especially
comparison, and is not unique to PHP. Often numbers will be off by some
miniscule amount, just enough to make them not equal.
What I would do in this situation is create a function float_equals(),
after deciding what delta is acceptable for your situation, like this:
define('MAX_FLOAT_DELTA', 0.001); // Or whatever is acceptable for you
function float_equals($a, $b) {
return (abs($a - $b) <= MAX_FLOAT_DELTA);
}
Then use float_equals($x, $y) instead of $x == $y.
Jasper
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