HYPOT(3)                   POSIX Programmer's Manual                  HYPOT(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       hypot, hypotf, hypotl -- Euclidean distance function

SYNOPSIS
       #include <math.h>

       double hypot(double _x, double _y);
       float hypotf(float _x, float _y);
       long double hypotl(long double _x, long double _y);

DESCRIPTION
       The functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2017
       defers to the ISO C standard.

       These functions shall compute the value of the square root of _x2+_y2
       without undue overflow or underflow.

       An application wishing to check for error situations should set errno
       to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
       FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
       occurred.

RETURN VALUE
       Upon successful completion, these functions shall return the length of
       the hypotenuse of a right-angled triangle with sides of length _x and _y.

       If the correct value would cause overflow, a range error shall occur
       and hypot(), hypotf(), and hypotl() shall return the value of the macro
       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

       If _x or _y is +-Inf, +Inf shall be returned (even if one of _x or _y is
       NaN).

       If _x or _y is NaN, and the other is not +-Inf, a NaN shall be returned.

       If both arguments are subnormal and the correct result is subnormal, a
       range error may occur and the correct result shall be returned.

ERRORS
       These functions shall fail if:

       Range Error The result overflows.

                   If the integer expression (math__errhandling & MATH_ERRNO)
                   is non-zero, then errno 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.

       These functions may fail if:

       Range Error The result underflows.

                   If the integer expression (math__errhandling & MATH_ERRNO)
                   is non-zero, then errno 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.

       The following sections are informative.

EXAMPLES
       See the EXAMPLES section in atan2().

APPLICATION USAGE
       hypot(_x,_y), hypot(_y,_x), and hypot(_x, -_y) are equivalent.

       hypot(_x, +-0) is equivalent to fabs(_x).

       Underflow only happens when both _x and _y are subnormal and the
       (inexact) result is also subnormal.

       These functions take precautions against overflow during intermediate
       steps of the computation.

       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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       atan2(), feclearexcept(), fetestexcept(), isnan(), sqrt()

       The Base Definitions volume of POSIX.1-2017, Section 4.20, Treatment of
       Error Conditions for Mathematical Functions, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             HYPOT(3)
