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

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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
       These functions shall compute the value of the  square  root  of  x**2+
       y**2 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 is 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
       None.
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  (inex-
       act) 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
       feclearexcept(), fetestexcept(), isnan(), sqrt(), the Base  Definitions
       volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi-
       tions for Mathematical Functions, <math.h>
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 .

IEEE/The Open Group                  2003                            HYPOT(3P)