erf(3)                              CLIX                              erf(3)



  NAME

    erf, erfc - Computes the error and complementary error functions

  LIBRARY

    Math Library (libm.a)

    Intergraph Math Library (libmath.a)

  SYNOPSIS

    #include <math.h>
    double erf(
      double x );

    double erfc(
      double x );

  PARAMETERS

    x      Specifies a double value.

  DESCRIPTION

    The erf() function computes the error function of x, defined as:
       x
    _2_∫e-t2dt
    \|π0
    The erfc() function computes 1.0 - erf(x).

    The erfc() function is provided because of the significant loss of
    relative accuracy if erf(x) is called for large values of x and the result
    is subtracted from 1.0.  For example, 12 decimal places are lost when
    calculating (1.0- erf(5)).

  NOTES

    The erf() and erfc() functions are supported for multi-threaded
    applications.

  RETURN VALUES

    Upon successful completion, the erf() and erfc() functions return the
    value of the error function and complementary error function,
    respectively.  If x is NaN, NaN is returned.  Otherwise, errno is set to
    indicate the error or NaN is returned.

  ERRORS

    If the erf() or erfc() function fails, errno may be set to the following



  2/94 - Intergraph Corporation                                              1

  erf(3)                              CLIX                              erf(3)



    value:

    [EDOM]    The value of x is NaN.

  RELATED INFORMATION

    Functions:  exp(3), isnan(3)















































  2                                              Intergraph Corporation - 2/94