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.

SEE ALSO

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

COLOPHON

   This  page  is  part of release 4.09 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/.


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