| .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) |
| .\" |
| .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE) |
| .\" Distributed under GPL |
| .\" %%%LICENSE_END |
| .\" |
| .TH CLOG 3 2021-03-22 "" "Linux Programmer's Manual" |
| .SH NAME |
| clog, clogf, clogl \- natural logarithm of a complex number |
| .SH SYNOPSIS |
| .nf |
| .B #include <complex.h> |
| .PP |
| .BI "double complex clog(double complex " z ); |
| .BI "float complex clogf(float complex " z ); |
| .BI "long double complex clogl(long double complex " z ); |
| .PP |
| Link with \fI\-lm\fP. |
| .fi |
| .SH DESCRIPTION |
| These functions calculate the complex natural logarithm of |
| .IR z , |
| with a branch cut along the negative real axis. |
| .PP |
| The logarithm |
| .BR clog () |
| is the inverse function of the exponential |
| .BR cexp (3). |
| Thus, if \fIy\ =\ clog(z)\fP, then \fIz\ =\ cexp(y)\fP. |
| The imaginary part of |
| .I y |
| is chosen in the interval [\-pi,pi]. |
| .PP |
| One has: |
| .PP |
| .nf |
| clog(z) = log(cabs(z)) + I * carg(z) |
| .fi |
| .PP |
| Note that |
| .I z |
| close to zero will cause an overflow. |
| .SH VERSIONS |
| These functions first appeared in glibc in version 2.1. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR clog (), |
| .BR clogf (), |
| .BR clogl () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| C99, POSIX.1-2001, POSIX.1-2008. |
| .SH SEE ALSO |
| .BR cabs (3), |
| .BR cexp (3), |
| .BR clog10 (3), |
| .BR clog2 (3), |
| .BR complex (7) |
