delim $$

     NAME
          erf, erfc - error function

     SYNOPSIS
          #include <math.h>

          double erf(x)
          double x;

          double erfc(x)
          double x;

     DESCRIPTION
          These functions calculate the error function erf(x) and the
          complementary error function erfc(x) = 1 - erf(x).  The
          error criterion for both erf and erfc is relative.

     DIAGNOSTICS
          There are no error returns.