Natural logarithm of 1 plus the argument

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double __far log1p(double x); (C99)

[Return value]

Returns the natural logarithm of 1 plus x.

If x is smaller than -1, returns a Not-a-Number (NaN) and sets macro EDOM to global variable errno.

If x is -1, returns -HUGE_VAL and sets macro ERANGE to global variable errno.

[Description]

This function calculates the natural logarithm of 1 plus x.