Manual Pages  — CLOG

clog, clogf and clogl – complex natural logarithm functions

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES SEE ALSO STANDARDS

Math Library (libm, -lm)

#include <complex.h>

double complex
clog(double complex z);

float complex
clogf(float complex z);

long double complex
clogl(long double complex z);

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

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* π , +I* π ] along the imaginary axis. The function satisfies the relationship: clog(conj(z)) = conj(clog(z)).

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

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