.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "<complex.h>" 0P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" <complex.h> 
.SH NAME
complex.h \- complex arithmetic
.SH SYNOPSIS
.LP
\fB#include <complex.h>\fP
.SH DESCRIPTION
.LP
The \fI<complex.h>\fP header shall define the following macros:
.TP 7
complex
Expands to \fB_Complex\fP.
.TP 7
_Complex_I
Expands to a constant expression of type \fBconst float _Complex\fP,
with the value of the imaginary unit (that is, a number
\fIi\fP such that \fIi\fP**2=-1).
.TP 7
imaginary
Expands to \fB_Imaginary\fP.
.TP 7
_Imaginary_I
Expands to a constant expression of type \fBconst float _Imaginary\fP
with the value of the imaginary unit.
.TP 7
I
Expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
defined, I expands to _Complex_I.
.sp
.LP
The macros imaginary and _Imaginary_I shall be defined if and only
if the implementation supports imaginary types.
.LP
An application may undefine and then, perhaps, redefine the complex,
imaginary, and I macros.
.LP
The following shall be declared as functions and may also be defined
as macros. Function prototypes shall be provided.
.sp
.RS
.nf

\fBdouble               cabs(double complex);
float                cabsf(float complex);
long double          cabsl(long double complex);
double complex       cacos(double complex);
float complex        cacosf(float complex);
double complex       cacosh(double complex);
float complex        cacoshf(float complex);
long double complex  cacoshl(long double complex);
long double complex  cacosl(long double complex);
double               carg(double complex);
float                cargf(float complex);
long double          cargl(long double complex);
double complex       casin(double complex);
float complex        casinf(float complex);
double complex       casinh(double complex);
float complex        casinhf(float complex);
long double complex  casinhl(long double complex);
long double complex  casinl(long double complex);
double complex       catan(double complex);
float complex        catanf(float complex);
double complex       catanh(double complex);
float complex        catanhf(float complex);
long double complex  catanhl(long double complex);
long double complex  catanl(long double complex);
double complex       ccos(double complex);
float complex        ccosf(float complex);
double complex       ccosh(double complex);
float complex        ccoshf(float complex);
long double complex  ccoshl(long double complex);
long double complex  ccosl(long double complex);
double complex       cexp(double complex);
float complex        cexpf(float complex);
long double complex  cexpl(long double complex);
double               cimag(double complex);
float                cimagf(float complex);
long double          cimagl(long double complex);
double complex       clog(double complex);
float complex        clogf(float complex);
long double complex  clogl(long double complex);
double complex       conj(double complex);
float complex        conjf(float complex);
long double complex  conjl(long double complex);
double complex       cpow(double complex, double complex);
float complex        cpowf(float complex, float complex);
long double complex  cpowl(long double complex, long double complex);
double complex       cproj(double complex);
float complex        cprojf(float complex);
long double complex  cprojl(long double complex);
double               creal(double complex);
float                crealf(float complex);
long double          creall(long double complex);
double complex       csin(double complex);
float complex        csinf(float complex);
double complex       csinh(double complex);
float complex        csinhf(float complex);
long double complex  csinhl(long double complex);
long double complex  csinl(long double complex);
double complex       csqrt(double complex);
float complex        csqrtf(float complex);
long double complex  csqrtl(long double complex);
double complex       ctan(double complex);
float complex        ctanf(float complex);
double complex       ctanh(double complex);
float complex        ctanhf(float complex);
long double complex  ctanhl(long double complex);
long double complex  ctanl(long double complex);
\fP
.fi
.RE
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
Values are interpreted as radians, not degrees.
.SH RATIONALE
.LP
The choice of \fII\fP instead of \fIi\fP for the imaginary unit concedes
to the widespread use of the identifier \fIi\fP for
other purposes. The application can use a different identifier, say
\fIj\fP, for the imaginary unit by following the inclusion of
the \fI<complex.h>\fP header with:
.sp
.RS
.nf

\fB#undef I
#define j _Imaginary_I
\fP
.fi
.RE
.LP
An \fII\fP suffix to designate imaginary constants is not required,
as multiplication by \fII\fP provides a sufficiently
convenient and more generally useful notation for imaginary terms.
The corresponding real type for the imaginary unit is
\fBfloat\fP, so that use of \fII\fP for algorithmic or notational
convenience will not result in widening types.
.LP
On systems with imaginary types, the application has the ability to
control whether use of the macro I introduces an imaginary
type, by explicitly defining I to be _Imaginary_I or _Complex_I. Disallowing
imaginary types is useful for some applications
intended to run on implementations without support for such types.
.LP
The macro _Imaginary_I provides a test for whether imaginary types
are supported.
.LP
The \fIcis\fP() function (\fIcos\fP(\fIx\fP) + \fII\fP*\fIsin\fP(\fIx\fP))
was considered but rejected because its
implementation is easy and straightforward, even though some implementations
could compute sine and cosine more efficiently in
tandem.
.SH FUTURE DIRECTIONS
.LP
The following function names and the same names suffixed with \fIf\fP
or \fIl\fP are reserved for future use, and may be added
to the declarations in the \fI<complex.h>\fP header.
.TS C
center; lw(26) lw(26) lw(26).
T{
.br
\fIcerf\fP()
.br
\fIcerfc\fP()
.br
\fIcexp2\fP()
.br
\ 
T}	T{
.br
\fIcexpm1\fP()
.br
\fIclog10\fP()
.br
\fIclog1p\fP()
.br
\ 
T}	T{
.br
\fIclog2\fP()
.br
\fIclgamma\fP()
.br
\fIctgamma\fP()
.br
\ 
T}
.TE
.SH SEE ALSO
.LP
The System Interfaces volume of IEEE\ Std\ 1003.1-2001, \fIcabs\fP(),
\fIcacos\fP(), \fIcacosh\fP(), \fIcarg\fP(), \fIcasin\fP(), \fIcasinh\fP(),
\fIcatan\fP(), \fIcatanh\fP(), \fIccos\fP(), \fIccosh\fP(), \fIcexp\fP(),
\fIcimag\fP(), \fIclog\fP(), \fIconj\fP(), \fIcpow\fP(), \fIcproj\fP(),
\fIcreal\fP(), \fIcsin\fP(), \fIcsinh\fP(), \fIcsqrt\fP(), \fIctan\fP(),
\fIctanh\fP()
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .