clog2.3m (2010 09)

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clog2(3M) clog2(3M)

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NAME

clog2(), clog2f(), clog2l(), clog2w(), clog2q() - complex base-2 logarithm functions

SYNOPSIS

#include <complex.h>

double complex clog2(double complex z);

float complex clog2f(float complex z);

long double complex clog2l(long double complex z);

extended complex clog2w(extended complex

z);

quad complex clog2q(quad complex z);

DESCRIPTION

clog2() returns the complex base-2 logarithm of z in the range of a strip mathematically unbounded

along the real axis and in the interval [-iPi/

log(2),+iPi/log(2)] along the imaginary axis. There is a

branch cut along the negative real axis.

clog2f() is a float complex version of clog2()

; it takes a float complex argument and

returns a

float complex result.

clog2l() is a long double complex version of clog2(); it takes a long double complex argu-

ment and returns a long double complex result.

clog2w() is an extended complex version of clog2(); it takes an extended complex argument

and returns an extended complex result.

clog2q() is equivalent to clog2l() on HP-UX systems.

USAGE

To use these functions, compile with the default

-Ae option. To use clog2w()

or clog2q(), compile

with the

-fpwidetypes option. Make sure your program includes <complex.h>. Link in the math

library by specifying -lm on the compiler or linker command line.

RETURN VALUE

clog2(conj(z)) = conj(clog2(z)).

clog2(-0+i0) returns -Inf+iPi/log(2) and raises the divide-by-zero ﬂoating-point exception.

clog2(+0+i0) returns -Inf+i0 and raises the divide-by-zero ﬂoating-point exception.

clog2(x+iInf) returns +Inf+iPi/(2log(2)), for ﬁnite x.

clog2(x+iNaN) returns NaN+iNaN and optionally raises the invalid ﬂoating-point exception, for ﬁnite

clog2(-Inf+iy) returns +Inf+iPi/log(2), for ﬁnite positive-signed y.

clog2(+Inf+iy) returns +Inf+i0, for ﬁnite positive-signed y.

clog2(-Inf+iInf) returns +Inf+i3Pi/(4log(2)).

clog2(+Inf+iInf) returns +Inf+iPi/(4log(2)).

clog2(±Inf+iNaN) returns +Inf+iNaN.

clog2(NaN+iy) returns NaN+iNaN and optionally raises the invalid ﬂoating-point exception, for ﬁnite

clog2(NaN+iInf) returns +Inf+iNaN.

clog2(NaN+iNaN) returns NaN+iNaN.

ERRORS

No errors are deﬁned.