expm1

(PHP 4 >= 4.0.7, PHP 5)

expm1 — Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero

설명

float expm1 ( float $arg )

Warning

This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function at your own risk.

expm1() returns the equivalent to 'exp(arg ) - 1' computed in a way that is accurate even if the value of arg is near zero, a case where 'exp (arg ) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal.

Note: 이 함수는 윈도우 플랫폼에서는 작동하지 않습니다.

매개변수

arg: The argument to process

반환값

'e' to the power of arg minus one

참고

add a note User Contributed Notes
expm1

hagen at von-eitzen dot de
24-Feb-2003 03:57


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);

}

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floor

exp

Last updated: Sun, 25 Nov 2007