# Build table layout of elements `E` for the holder `h`.
	#
	# `null` is used to fill places without elements (holes).
	fun build_layout(h: H): Array[nullable E]
	do
		var table = new Array[nullable E]
		for s in poset[h].greaters do
			var bucket = buckets.get_or_null(s)
			if bucket == null then continue
			for e in bucket do
				var color = colors[e]
				if table.length <= color then
					for i in [table.length .. color[ do
						table[i] = null
					end
				else
					assert table[color] == null else print "in {h}, for {color}: {table[color] or else ""} vs {e}"
				end
				table[color] = e
			end
		end
		return table
	end