PHP does not have the following math function in any extensions:
frexp() - Extract Mantissa and Exponent of the Floating-Point Value
I've digged many C source codes, and found the simplest implementation as follows:
<?php
function frexp ( $float ) {
$exponent = ( floor(log($float, 2)) + 1 );
$mantissa = ( $float * pow(2, -$exponent) );
return(
array($mantissa, $exponent)
);
}
print_r(frexp(0.0345));
print_r(frexp(21.539));
?>
Array
(
[0] => 0.552
[1] => -4
)
Array
(
[0] => 0.67309375
[1] => 5
)
I have compared the results using a lot of floats against C's frexp function - they are the same.
Note that C and PHP uses different float precisions, for example "4619.3" gives:
C: 0.56387939453125, 13
PHP: 0.563879394531, 13
/Assuming default configurations./
