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).

       allbox; lbw21 lb lb l l l.  Interface Attribute Value T{ erf(), erff(),
       erfl() T}   Thread safety  MT-Safe

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

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

SEE ALSO
       cerf(3), erfc(3), exp(3)

COLOPHON
       This  page  is  part of release 4.16 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.



GNU                               2017-09-15                            ERF(3)