ERF(3)
Linux Programmer’s Manual
ERF(3)
NAME
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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or cc -std=c99
erff(), erfl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600|| _ISOC99_SOURCE; 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.
CONFORMING TO
C99, POSIX.1-2001. 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 3.24 of the Linux man-pages project. A description of the project, and informa-
tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
GNU
2008-08-05
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