Compare this to log1p (which is its inverse).
Also, You may have to use a similar workaraound in case the underlying C library
does not support expm1:
function expm1($x) {
return ($x>-1.0e-6 && $x<1.0e-6) ? ($x + $x*$x/2) : (exp($x)-1);
}
expm1(PHP 4 >= 4.1.0, PHP 5) expm1 -- Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zeroDescriptionfloat expm1 ( float number )
expm1() returns the equivalent to 'exp(number) - 1' computed in a way that is accurate even if the value of number is near zero, a case where 'exp (number) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal.
expm1
hagen at von-eitzen dot de
24-Feb-2003 03:57
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exp