Obtain the natural logarithm

[Classification]

Mathematical library

[Syntax]

#include <math.h>

float __far logf(float x);

[Return value]

Returns the natural logarithm of x.

logf returns a Not-a-Number (NaN) and sets macro EDOM to global variable errno if x is negative.

If x is zero, it returns -∞ and sets macro ERANGE to global variable errno.

[Description]

This function calculates the natural logarithm of x, i.e., logarithm with base e.