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# erf(3)

GNU
2017-09-15
Aliases: erfc(3), erfc(3), erfc(3), erff(3), erff(3), erff(3), erff(3), erff(3), erff(3), erff(3), erff(3), erff(3), erff(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3), erfl(3)

### manpages-dev

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### man-pages

Linux kernel and C library user-space interface documentation

## 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():
_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).
 Interface Attribute Value Thread safety MT-Safe

## CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD.