.\" Copyright (c) 2006 Apple Computer .\" .Dd November 9, 2006 .Dt CLOG 3 .Os BSD 4 .Sh NAME .Nm clog .Nd complex logarithm function .Sh SYNOPSIS .Fd #include <complex.h> .Ft double complex .Fn clog "double complex z" .Ft long double complex .Fn clogl "long double complex z" .Ft float complex .Fn clogf "float complex z" .Sh DESCRIPTION .Fn clog "z" returns the complex logarithm of .Fa z . .Pp clog(conj(z)) = conj(clog(z)), for all complex floating-point numbers z. .Sh SPECIAL VALUES The conjugate symmetry of clog() is used to abbreviate the specification of special values. .Pp .Fn clog "-0 + 0i" returns -inf + Pi i and raises the divide-by-zero flag. .Pp .Fn clog "0 + 0i" returns -inf + 0i and raises the divide-by-zero flag. .Pp .Fn clog "x + inf i" returns inf + Pi/2 i, for finite x. .Pp .Fn clog "x + NaN i" returns NaN + NaN i. .Pp .Fn clog "-inf + yi" returns inf + Pi i, for finite positive y. .Pp .Fn clog "inf + yi" returns inf + 0i, for finite positive y. .Pp .Fn clog "-inf + inf i" returns inf + 3Pi/4 i. .Pp .Fn clog "inf + inf i" returns inf + Pi/4 i. .Pp .Fn clog "ħinf + NaN i" returns inf + NaN i. .Pp .Fn clog "NaN + yi" returns NaN + NaN i, for finite y. .Pp .Fn clog "NaN + inf i" returns inf + NaN i. .Pp .Fn clog "NaN + NaN i" returns NaN + NaN i. .Pp .Sh NOTES .Sh SEE ALSO .Xr cexp 3 .Xr log 3 .Xr complex 3 .Sh STANDARDS The .Fn clog function conforms to ISO/IEC 9899:1999(E).