[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    ERF(3) manual page Table of Contents

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 || _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

Multithreading (see pthreads(7) )

The erf(), erff(), and erfl() functions are thread-safe.

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 3.78 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 http://www.kernel.org/doc/man-pages/.

Table of Contents