ERF

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
COLOPHON

NAME

erf, erff, erfl, − error function

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():

_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

erff(), erfl():

_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

DESCRIPTION

The erf() function returns 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).

CONFORMING TO

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.