erf - Man Page

error function

Library

Math library (libm, -lm)

Synopsis

#include <math.h>

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

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

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

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).

Errors

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.

Attributes

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

InterfaceAttributeValue
erf(), erff(), erfl()Thread safetyMT-Safe

Standards

C11, POSIX.1-2008.

History

C99, POSIX.1-2001.

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

See Also

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

Referenced By

cerf(3), cerfcx(3), cerfi(3), erfc(3).

The man pages erff(3) and erfl(3) are aliases of erf(3).

2023-10-31 Linux man-pages 6.06