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log, logf : natural logarithms

Synopsis

Section titled “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.


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**Authoritative source**: BUSMASTER DITA help source `log.dita`, compiled into `BUSMASTER.CHM` with the application.