Natural logarithm of a complex number

**#include <complex.h>**

**double complex clog(double complex ***z***);**

**float complex clogf(float complex ***z***);**

**long double complex clogl(long double complex ***z***);**

Link with *-lm*.

The logarithm **clog**() is the inverse function of the exponential **cexp**(3). Thus, if *y = clog(z)*, then *z = cexp(y)*. The imaginary part of *y* is chosen in the interval [-pi,pi].

One has:

clog(z) = log(cabs(z)) + I * carg(z)

Note that *z* close to zero will cause an overflow.

These functions first appeared in glibc in version 2.1.

C99.

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