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   erf    ( 3 )

функция ошибки (error function)

Имя (Name)

erf, erff, erfl - error function

Синопсис (Synopsis)

#include <math.h>

double erf(double x); float erff(float x); long double erfl(long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

erf(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

erff(), erfl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


Описание (Description)

These functions return the error function of x, defined as

erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(-t*t) dt


Возвращаемое значение (Return value)

On success, these functions return the value of the error
       function of x, a value in the range [-1, 1].

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is positive infinity (negative infinity), +1 (-1) is returned.

If x is subnormal, a range error occurs, and the return value is 2*x/sqrt(pi).


Ошибки (Error)

See math_error(7) for information on how to determine whether an
       error has occurred when calling these functions.

The following errors can occur:

Range error: result underflow (x is subnormal) An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno.


Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface Attribute Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │erf(), erff(), erfl() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘


Стандарты (Conforming to)

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD.


Смотри также (See also)

cerf(3), erfc(3), exp(3)