dlinfo.3: ATTRIBUTES: Note function that is thread-safe

[thirdparty/man-pages.git] / man3 / carg.3

.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" Distributed under GPL
.\" %%%LICENSE_END
.\"
.TH CARG 3 2015-04-19 "" "Linux Programmer's Manual"
.SH NAME
carg, cargf, cargl \- calculate the complex argument
.SH SYNOPSIS
.B #include <complex.h>
.sp
.BI "double carg(double complex " z ");"
.br
.BI "float cargf(float complex " z ");"
.br
.BI "long double cargl(long double complex " z ");"
.sp
Link with \fI\-lm\fP.
.SH DESCRIPTION
These functions calculate the complex argument (also called phase angle) of
.IR z ,
with a branch cut along the negative real axis.

A complex number can be described by two real coordinates.
One may use rectangular coordinates and gets

.nf
    z = x + I * y
.fi

where
.IR "x\ =\ creal(z)"
and
.IR "y\ =\ cimag(z)" .
.LP
Or one may use polar coordinates and gets
.nf

    z = r * cexp(I * a)

.fi
where
.IR "r\ =\ cabs(z)"
is the "radius", the "modulus", the absolute value of
.IR z ,
and
.IR "a\ =\ carg(z)"
is the "phase angle", the argument of
.IR z .
.LP
One has:
.nf

    tan(carg(z)) = cimag(z) / creal(z)
.fi
.SH RETURN VALUE
The return value is the range of [\-pi,pi].
.SH VERSIONS
These functions first appeared in glibc in version 2.1.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw24 lb lb
l l l.
Interface	Attribute	Value
T{
.BR carg (),
.BR cargf (),
.BR cargl ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
.SH SEE ALSO
.BR cabs (3),
.BR complex (7)