erf man page

erf, erff, erfl, — error function

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 versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

erff(), erfl():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 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 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

Conforming to

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

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

See Also

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

Colophon

This page is part of release 4.08 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Referenced By

erfc(3).

erff(3) and erfl(3) are aliases of erf(3).

2016-03-15 GNU Linux Programmer's Manual