erf(3) | Library Functions Manual | erf(3) |
NAME
erf, erff, erfl - error function
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>
double erf(double x); float erff(float x); long double erfl(long double x);
erf():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
erff(), erfl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 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 value of 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 |
erf (), erff (), erfl () | Thread safety | MT-Safe |
STANDARDS
C11, POSIX.1-2008.
HISTORY
C99, POSIX.1-2001.
The variant returning double also conforms to SVr4, 4.3BSD.
SEE ALSO
2024-05-02 | Linux man-pages 6.9.1 |