mirror of https://github.com/mkerrisk/man-pages
118 lines
3.8 KiB
Plaintext
118 lines
3.8 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
|
.TH "HYPOT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
|
.\" hypot
|
|
.SH NAME
|
|
hypot, hypotf, hypotl \- Euclidean distance function
|
|
.SH SYNOPSIS
|
|
.LP
|
|
\fB#include <math.h>
|
|
.br
|
|
.sp
|
|
double hypot(double\fP \fIx\fP\fB, double\fP \fIy\fP\fB);
|
|
.br
|
|
float hypotf(float\fP \fIx\fP\fB, float\fP \fIy\fP\fB);
|
|
.br
|
|
long double hypotl(long double\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);
|
|
.br
|
|
\fP
|
|
.SH DESCRIPTION
|
|
.LP
|
|
These functions shall compute the value of the square root of \fIx\fP**2+
|
|
\fIy\fP**2 without undue overflow or underflow.
|
|
.LP
|
|
An application wishing to check for error situations should set \fIerrno\fP
|
|
to zero and call
|
|
\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
|
|
On return, if \fIerrno\fP is non-zero or
|
|
\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
|
|
is non-zero, an error has occurred.
|
|
.SH RETURN VALUE
|
|
.LP
|
|
Upon successful completion, these functions shall return the length
|
|
of the hypotenuse of a right-angled triangle with sides of
|
|
length \fIx\fP and \fIy\fP.
|
|
.LP
|
|
If the correct value would cause overflow, a range error shall occur
|
|
and \fIhypot\fP(), \fIhypotf\fP(), and \fIhypotl\fP()
|
|
shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
|
|
respectively.
|
|
.LP
|
|
If
|
|
\fIx\fP or \fIy\fP is \(+-Inf, +Inf shall be returned (even if one
|
|
of \fIx\fP or \fIy\fP is NaN).
|
|
.LP
|
|
If \fIx\fP or \fIy\fP is NaN, and the other is not \(+-Inf, a NaN
|
|
shall be returned.
|
|
.LP
|
|
If both arguments are subnormal and the correct result is subnormal,
|
|
a range error may occur and the correct result is returned.
|
|
.SH ERRORS
|
|
.LP
|
|
These functions shall fail if:
|
|
.TP 7
|
|
Range\ Error
|
|
The result overflows.
|
|
.LP
|
|
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
|
|
then \fIerrno\fP shall be set to [ERANGE]. If the
|
|
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
|
|
then the overflow floating-point exception shall be
|
|
raised.
|
|
.sp
|
|
.LP
|
|
These functions may fail if:
|
|
.TP 7
|
|
Range\ Error
|
|
The result underflows.
|
|
.LP
|
|
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
|
|
then \fIerrno\fP shall be set to [ERANGE]. If the
|
|
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
|
|
then the underflow floating-point exception shall be
|
|
raised.
|
|
.sp
|
|
.LP
|
|
\fIThe following sections are informative.\fP
|
|
.SH EXAMPLES
|
|
.LP
|
|
None.
|
|
.SH APPLICATION USAGE
|
|
.LP
|
|
\fIhypot\fP(\fIx\fP,\fIy\fP), \fIhypot\fP(\fIy\fP,\fIx\fP), and \fIhypot\fP(\fIx\fP,
|
|
-\fIy\fP) are equivalent.
|
|
.LP
|
|
\fIhypot\fP(\fIx\fP, \(+-0) is equivalent to \fIfabs\fP(\fIx\fP).
|
|
.LP
|
|
Underflow only happens when both \fIx\fP and \fIy\fP are subnormal
|
|
and the (inexact) result is also subnormal.
|
|
.LP
|
|
These functions take precautions against overflow during intermediate
|
|
steps of the computation.
|
|
.LP
|
|
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
|
|
& MATH_ERREXCEPT) are independent of
|
|
each other, but at least one of them must be non-zero.
|
|
.SH RATIONALE
|
|
.LP
|
|
None.
|
|
.SH FUTURE DIRECTIONS
|
|
.LP
|
|
None.
|
|
.SH SEE ALSO
|
|
.LP
|
|
\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIisnan\fP() , \fIsqrt\fP()
|
|
, the Base Definitions volume of
|
|
IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions
|
|
for
|
|
Mathematical Functions, \fI<math.h>\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 .
|