erf, erff, erfl, - error function
#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():
_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
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
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).
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.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
erf (), erff (), erfl () |
Thread safety |
MT-Safe |
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD.
cerf(3),
erfc(3),
exp(3)