# clog(3) — Linux manual page

```clog(3)                 Library Functions Manual                 clog(3)
```

## NAME         top

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

## LIBRARY         top

```       Math library (libm, -lm)
```

## 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.
```

## 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 │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## STANDARDS         top

```       C11, POSIX.1-2008.
```

## HISTORY         top

```       glibc 2.1.  C99, POSIX.1-2001.
```

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