erf(3) - Linux man page
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.
Conforming To
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.