log1p, log1pf—log of 1 + x #include <math.h>
double log1p(double x);
float log1pf(float x);
Description
log1p calculates
the natural logarithm of 1+x. You can use log1p rather
than `log(1+x)' for greater precision when x is very
small.
log1pf calculates the same thing, but accepts and returns
float values rather than double.
Returns
log1p returns a double, the natural log of 1+x.
log1pf returns a float, the natural log of 1+x.
Portability
Neither log1p nor log1pf is required by ANSI C or by the System V
Interface Definition (Issue 2).