local ecs = require "ecs" local w = ecs.world() w:register { name = "v", type = "int", } w:register { name = "marked" } for i = 1, 10 do w:new { v = i, marked = i % 2 == 1, } end for v in w:select "v:in marked?in" do print(v.v, v.marked) end print "Marked" for v in w:select "v:in marked" do print(v.v) end print "Not Marked" for v in w:select "v:in marked:absent" do print(v.v) end