# File lib/cidr.rb, line 451
    def [](index)
        raise ArgumentError, "Integer expected for argument 'index' but " +
                             "#{index.class} provided." if (!index.kind_of?(Integer) )

        addr = @network + index
        if ( (@hostmask | addr) == (@hostmask | @network) )
            addr = NetAddr.cidr_build(@version, addr)
        else
            raise BoundaryError, "Index of #{index} returns IP that is out of " +
                                 "bounds of CIDR network."
        end

        return(addr)
    end