log
Computes the natural logarithm (base e) of x
#include <math.h>
double log (
double x);
The log function returns the natural logarithm of the argument. When the argument is outside the permissible range, errno is set and matherr is called. Unless matherr is replaced, matherr prints a diagnostic message using the stderr stream.
A domain error occurs if the argument is negative. A range error occurs if the argument is zero.
#include <math.h> #include <stdio.h> main () { printf ("%f\n", log (.5) ); }
produces the following:
-0.693147