#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)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
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
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.
The erf(), erff(), and erfl() functions are thread-safe.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.
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