Delicious Bookmark this on Delicious Share on Facebook SlashdotSlashdot It! Digg! Digg



PHP : Function Reference : Mathematical Functions : expm1

expm1

Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero (PHP 4 >= 4.0.7, PHP 5)
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:

This function is not implemented on Windows platforms.

Parameters

arg

The argument to process

Return Values

'e' to the power of arg minus one

See Also
log1p()
exp()

Code Examples / Notes » expm1

hagen

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);
}


Change Language


Follow Navioo On Twitter
abs
acos
acosh
asin
asinh
atan2
atan
atanh
base_convert
bindec
ceil
cos
cosh
decbin
dechex
decoct
deg2rad
exp
expm1
floor
fmod
getrandmax
hexdec
hypot
is_finite
is_infinite
is_nan
lcg_value
log10
log1p
log
max
min
mt_getrandmax
mt_rand
mt_srand
octdec
pi
pow
rad2deg
rand
round
sin
sinh
sqrt
srand
tan
tanh
eXTReMe Tracker