ERF

Section: Linux Programmer's Manual (3)
Updated: 2013-10-29
Index Return to Main 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

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Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
Multithreading (see pthreads(7))
CONFORMING TO
SEE ALSO
COLOPHON