| CLOG(3) | Linux Programmer's Manual | CLOG(3) |
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.
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| 2017-09-15 |