NAME | SYNOPSIS | DESCRIPTION | ERRORS (due to Roundoff) | RETURN VALUES | NOTES | ATTRIBUTES | SEE ALSO
#include <math.h>double exp(double x);
The exp function computes the exponential value of the given argument x .
The expm1 function computes the value exp(x)-1 accurately even for extremely small values of x .
The log function computes the natural logarithm of the argument x.
The log10 function computes the logarithm of argument x to base 10.
The log1p function computes the value of log(1+x) accurately even for extremely small values of x .
The pow computes the value of to the exponent
The exp(x), log(x), expm1(x) and log1p(x) functions are accurate to within a ulp , and log10(x) to within approximately 2 ulp s. A ulp is one Unit in the Last Place . The error in pow(x, y) is below about 2 ulp s when its magnitude is moderate, but increases as pow(x, y) approaches the over/underflow thresholds. Almost as many bits as are occupied by the floating-point format's exponent field could be lost; that is 11 bits for IEEE 754 Double. The worst errors observed during testing have been under 300 ulp s for IEEE 754 Double. Moderate values of pow are sufficiently accurate that pow(integer, integer) is precise until it is greater than 2**53 for IEEE 754.
These functions will return the appropriate computation unless an error occurs or an argument is out of range. The functions exp , expm1 and pow detect if the computed value will overflow, set errno to ERANGE and a system-dependent notification is performed. The pow(x, y) function checks whether x < 0 and y is not an integer; if this is true, errno is set to EDOM and a system-dependent notification is performed. errno is set to EDOM and a system-dependent notification is performed by log, unless x > 0, by log1p unless x > -1.
The function pow(x, 0) returns x**0 = 1 for all x including x = 0, , and NaN .
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
---|---|
Interface Stability | Evolving |
NAME | SYNOPSIS | DESCRIPTION | ERRORS (due to Roundoff) | RETURN VALUES | NOTES | ATTRIBUTES | SEE ALSO