**clog**

**CLOG(3)** Linux Programmer's Manual **CLOG(3)**
NAME
clog, clogf, clogl - natural logarithm of a complex number
SYNOPSIS
#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.
DESCRIPTION
These functions calculate the complex natural logarithm of z, with a
branch cut along the negative real axis.
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.
VERSIONS
These functions first appeared in glibc in version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
**attributes(7)**.
+-------------------------+---------------+---------+
|Interface | Attribute | Value |
+-------------------------+---------------+---------+
|clog(), clogf(), clogl() | Thread safety | MT-Safe |
+-------------------------+---------------+---------+
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
SEE ALSO
**cabs(3)**, **cexp(3)**, **clog10(3)**, **clog2(3)**, **complex(7)**
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2017-09-15 **CLOG(3)**

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