::math::stats::proportional_weighted_shares --
        #
        # Return the proportional_weighted_shares from quantity by two or more given ratios
        #
        # Arguments:
        #    quantity   first value is quantity
        #    args       second, third,  and sucessive values
        #               are two or more given ratios (usually integers in high school)
        #               However, decimal fractions for both quantity and args seem
        #               to be reasonably accurate to TCL precison.
        # Conditions and answer checks
        #       The quantity must be larger than 0
        #       The number of args must be larger than 2
        #       If sum of parts equals zero, formula is undefined
        #       Number of parts should be equal to [ llength $args ]
        #       Total value of parts should be equal to quantity entry
        #       The solution may not be unique in that more than one
        #       set of shares may have or generate the same multiple ratios.
        # Results: parts of quantity into proportional weighted shares