/*****************************************************************************
*                                                                            *
*   PROD.SPL    Copyright (C) 1998-2003 DSP Development Corporation          *
*                               All Rights Reserved                          *
*                                                                            *
*   Author:      Matthew Tom                                                 *
*                                                                            *
*   Synopsis:    Calculates the product of the entries of a series           *
*                                                                            *
*   Revisions:    3 May 1998  MAT  Creation                                  *
*                 9 Jun 1998  MAT  Help Menu Entry                           *
*                13 Apr 2000  RRR  colreduce                                 *
*                27 Jul 2001  RRR  refseries                                 *
*                21 Feb 2003  RRR  prod({}) == 1                             *
*                                                                            *
*****************************************************************************/

#include 

#if @HELP_PROD

    PROD

    Purpose: Calculates the product of all values of a series or array.

    Syntax:  PROD(x)

              x - input series or array, defaults to current window

    Returns: A scalar

    Example:

         PROD({5, 9, 2, 0.5})


         returns 45

    Example:

         a = {{1, 2, 3},
              {4, 5, 6},
              {7, 8, 9}}

         PROD(a)


         returns 362880


    See Also:
             Colprod
             Sum

#endif


/* product of a series or array */
prod(s)
{
        local r;

        /* default to current series */
        if (argc < 1) s = refseries(1);

        /* convert to series if required */
        if (not(isarray(s)))
        {
                s = castseries(s);
        }

        if (length(s) == 0)
        {
                /* special case for empty series */
                r = 1;
        }
        else
        {
                /* unravel in case input is array - colreduce does the rest */
                r = colreduce(unravel(s), "*");

                /* cast to scalar */
                if (iscomplx(r)) r = castcomplex(r);
                else r = castreal(r);
        }

        return(r);
}