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ERF(3) Linux Programmer's Manual ERF(3)

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():
         _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

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 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 |
     +----------------------+---------------+---------+

CONFORMING TO

     C99, POSIX.1-2001, POSIX.1-2008.

     The variant returning double also conforms to SVr4, 4.3BSD.