fun computeminmax(o: MGroup) do
		if not tree.sub.has_key(o) then
			mins[o] = null
			maxs[o] = null
			return
		end
		var subs = tree.sub[o]
		var minres = mini(subs.first)
		var maxres = maxi(subs.first)
		var order = o.model.mmodule_importation_hierarchy
		for o2 in subs do
			var c = mini(o2)
			if c == null then continue
			if minres == null or order.compare(minres, c) > 0 then minres = c
			c = maxi(o2)
			if c == null then continue
			if maxres == null or order.compare(maxres, c) < 0 then maxres = c
		end
		mins[o] = minres
		maxs[o] = maxres
		#if minres != maxres then print "* {o} {minres}..{maxres}"
	end