*       # Return range n1 .. n2
        define('range(n1,n2)') :(range_end)
range   range = range n1 ','; n1 = lt(n1,n2) n1 + 1 :s(range)
        range rtab(1) . range :(return)
range_end

        define('rangex(range)d1,d2')
        num = ('-' | '') span('0123456789') :(rangex_end)
rangex  range num . d1 '-' num . d2 = range(d1,d2) :s(rangex)
        rangex = range :(return)
rangex_end

*       # Test and display
        output = rangex('-6,-3--1,3-5,7-11,14,15,17-20')
end