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.

SEE ALSO

       cerf(3), erfc(3), exp(3)

COLOPHON

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