log2.3: Fixed feature test macro requirements

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

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH HYPOT 3 2008-08-05 ""  "Linux Programmer's Manual"
.SH NAME
hypot, hypotf, hypotl \- Euclidean distance function
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double hypot(double " x ", double " y );
.br
.BI "float hypotf(float " x ", float " y );
.br
.BI "long double hypotl(long double " x ", long double " y );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR hypot ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or
.I cc\ -std=c99
.br
.BR hypotf (),
.BR hypotl ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
The
.BR hypot ()
function returns
.RI sqrt( x * x + y * y ).
This is the length of the hypotenuse of a right-angled triangle
with sides of length
.I x
and
.IR y ,
or the distance of the point
.RI ( x , y )
from the origin.

The calculation is performed without undue overflow or underflow
during the intermediate steps of the calculation.
.\" e.g., hypot(DBL_MIN, DBL_MIN) does the right thing, as does, say
.\" hypot(DBL_MAX/2.0, DBL_MAX/2.0).
.SH RETURN VALUE
On success, these functions return the length of a right-angled triangle
with sides of length
.I x
and
.IR y .

If
.I x
or
.I y
is an infinity,
positive infinity is returned.

If
.I x
or
.I y
is a NaN,
and the other argument is not an infinity,
a NaN is returned.

If the result overflows,
a range error occurs,
and the functions return
.BR HUGE_VAL ,
.BR HUGE_VALF ,
or
.BR HUGE_VALL ,
respectively.

If both arguments are subnormal, and the result is subnormal,
.\" Actually, could the result not be subnormal if both arguments
.\" are subnormal?  I think not -- mtk, Jul 2008
a range error occurs,
and the correct result is returned.
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.PP
The following errors can occur:
.TP
Range error: result overflow
.I errno
is set to
.BR ERANGE .
An overflow floating-point exception
.RB ( FE_OVERFLOW )
is raised.
.TP
Range error: result underflow
.\" .I errno
.\" is set to
.\" .BR ERANGE .
An underflow floating-point exception
.RB ( FE_UNDERFLOW )
is raised.
.IP
These functions do not set
.IR errno
for this case.
.\" FIXME . Is it intentional that these functions do not set errno?
.\" They do set errno for the overflow case.
.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6795
.SH "CONFORMING TO"
C99, POSIX.1-2001.
The variant returning
.I double
also conforms to
SVr4, 4.3BSD.
.SH "SEE ALSO"
.BR cabs (3),
.BR sqrt (3)