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)

1  –  Argument

 x

    A radian expressed as a real number.

2  –  Description

    The erf functions return the error function of x, where erf(x),
    erff(x), and erfl(x) equal 2/sqrt(pi) times the area under the
    curve e**(-t**2) between 0 and x.

    The erfc functions return (1.0 - erf(x)). The erfc function can
    result in an underflow as x gets large.

3  –  Return Values

    x                  The value of the error function (erf) or
                       complementary error function (erfc).
    NaN                x is NaN; errno is set to EDOM.
    0                  Underflow occurred; errno is set to ERANGE.