log, logf[natural logarithms]

log, logf
[natural logarithms]

SYNOPSIS

#include <math.h> 
double log(double x); 
float logf(float x);

DESCRIPTION
Return the natural logarithm of x, that is, its logarithm base, e (where e is the base of the natural system of logarithms, 2.71828...). log and logf are identical, save for the return and argument types.

You can use the (non-ANSI) function, matherr, to specify error handling for these functions.

RETURNS
Normally, returns the calculated value. When x is zero, the returned value is -HUGE_VAL and errno is set to ERANGE. When x is negative, the returned value is -HUGE_VAL and errno is set to EDOM. You can control the error behavior via matherr.

COMPLIANCE
log is ANSI, logf is an extension.