log1p : log1p « math.h « C Tutorial

Item	Value
Header file	math.h
Declaration	float log1pf(float num); double log1p(double num); long double log1pl(long double num);
Return	returns the natural logarithm for num+1.

#include <math.h>
  #include <stdio.h>

  int main(void)
  {
    double val = 1.0;

    do {
      printf("%f %f\n", val, log1p (val));
      val++;
    } while (val<11.0);

    return 0;
  }

1.000000 0.693147
2.000000 1.098612
3.000000 1.386294
4.000000 1.609438
5.000000 1.791759
6.000000 1.945910
7.000000 2.079442
8.000000 2.197225
9.000000 2.302585
10.000000 2.397895

19.44.log1p
	19.44.1.	log1p