```CLOG(3)                   Linux Programmer's Manual                  CLOG(3)
```

## NAME         top

```       clog, clogf, clogl - natural logarithm of a complex number
```

## SYNOPSIS         top

```       #include <complex.h>

double complex clog(double complex z);
float complex clogf(float complex z);
long double complex clogl(long double complex z);

```

## DESCRIPTION         top

```       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         top

```       These functions first appeared in glibc in version 2.1.
```

## ATTRIBUTES         top

```       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         top

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

```       cabs(3), cexp(3), clog10(3), clog2(3), complex(7)
```

## COLOPHON         top

```       This page is part of release 5.01 of the Linux man-pages project.  A
description of the project, information about reporting bugs, and the
https://www.kernel.org/doc/man-pages/.

2017-09-15                          CLOG(3)
```