NAME

clog, clogf and clogl — complex natural logarithm functions

LIBRARY

Math Library (libm, -lm)

SYNOPSIS

#include <complex.h>

double complex
clog(double complex z);

float complex
clogf(float complex z);

long double complex
clogl(long double complex z);

DESCRIPTION

The clog(), clogf(), and clogl() functions compute the complex natural logarithm of z. with a branch cut along the negative real axis .

RETURN VALUES

The clog() function returns the complex natural logarithm value, in the range of a strip mathematically unbounded along the real axis and in the interval [-I* pi , +I* pi ] along the imaginary axis. The function satisfies the relationship: clog(conj(z)); = conj(clog(z));.

Argument	Return value	Comment
-0 + I*0	-infinity + I*pi	Divide-by-zero exception
		raised
+0 + I*0	-infinity + I*0	Divide by zero exception
		raised
x + I*infinity	+infinity + I*pi/2	For finite x
x + I*NaN	NaN + I*NaN	Optionally raises invalid
		floating-point exception
		for finite x
-infinity + I*y	+infinity + I*pi	For finite positive-signed y
+infinity + I*y	+infinity + I*0	For finite positive-signed y
-infinity + I*infinity	+infinity + I*3pi/4
+infinity + I*infinity	+infinity + I*pi/4
±infinity + I*NaN	+infinity + I*NaN
NaN + I*y	NaN + I*NaN	Optionally raises invalid
		floating-point exception
		for finite y
NaN + I*infinity	+infinity + I*NaN
NaN + I*NaN	NaN + I*NaN

STANDARDS

The clog(), cexpf(), and clogl() functions conform to ISO/IEC 9899:1999 (“ISO C99”).