Returns the error function of its argument.

    Format

      #include  <math.h>

      double erf  (double x);

      float erff  (float x); (Integrity servers, Alpha)

      long double erfl  (long double x); (Integrity servers, Alpha)

      double erfc  (double x); (Integrity servers, Alpha)

      float erfcf  (float x); (Integrity servers, Alpha)

      long double erfcl  (long double x); (Integrity servers, Alpha)