функция евклидова расстояния (euclidean distance function)
Пролог (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.
Имя (Name)
hypot, hypotf, hypotl — Euclidean distance function
Синопсис (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);
Описание (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.
Возвращаемое значение (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.
Ошибки (Error)
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.
Примеры (Examples)
See the EXAMPLES section in atan2().
Использование в приложениях (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.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
atan2(3p), feclearexcept(3p), fetestexcept(3p), isnan(3p),
sqrt(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
