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CLOG(3) FreeBSD Library Functions Manual CLOG(3) 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 SEE ALSO complex(3), log(3), math(3) STANDARDS The clog(), cexpf(), and clogl() functions conform to ISO/IEC 9899:1999 ("ISO C99"). FreeBSD 14.0-RELEASE-p11 June 6, 2018 FreeBSD 14.0-RELEASE-p11