дополнительные функции ошибок (complementary error functions)
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)
erfc, erfcf, erfcl — complementary error functions
Синопсис (Synopsis)
#include <math.h>
double erfc(double x);
float erfcf(float x);
long double erfcl(long double x);
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 complementary error function
1.0 - erf(x).
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
value of the complementary error function.
If the correct value would cause underflow, and is not
representable, a range error may occur, and erfc(), erfcf(), and
erfcl() shall return 0.0, or (if the IEC 60559 Floating-Point
option is not supported) an implementation-defined value no
greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN,
respectively.
If x is NaN, a NaN shall be returned.
If x is ±0, +1 shall be returned.
If x is -Inf, +2 shall be returned.
If x is +Inf, +0 shall be returned.
If the correct value would cause underflow and is representable,
a range error may occur and the correct value shall be returned.
Ошибки (Error)
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)
None.
Использование в приложениях (Application usage)
The erfc() function is provided because of the extreme loss of
relative accuracy if erf(x) is called for large x and the result
subtracted from 1.0.
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)
erf(3p), feclearexcept(3p), fetestexcept(3p), isnan(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
