clog, clogf, clogl - 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`

.

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.

These functions first appeared in glibc in version 2.1.

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |

clog(), clogf(), clogl() | Thread safety | MT-Safe |

C99, POSIX.1-2001, POSIX.1-2008.

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/.