erf(), erff(), erfl()

Updated: April 19, 2023

Compute the error function of a number

Synopsis:

#include <math.h>

double erf ( double x );

float erff ( float x );

long double erfl ( long double x );

Arguments:

x
The number for which you want to compute the error function.

Library:

libm
The general-purpose math library.
libm-sve
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.

Description:

The erf(), erff(), and erfl() functions compute the following:

If x is large and the result of erf() is subtracted from 1.0, the results aren't very accurate; use erfc() instead.

This equality is true: erf(-x) = -erf(x)

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Returns:

The value of the error function.

If x is: These functions return: Errors:
±0.0 0.0, with the same sign as x
A value that would cause underflow x FE_UNDERFLOW
±Inf 1.0, with the same sign as x
NaN NaN

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

Classification:

C11, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes