const In : set set prop term iIn = In infix iIn 2000 2000 term Subq = \x:set.\y:set.!z:set.z iIn x -> z iIn y term nIn = \x:set.\y:set.~ x iIn y const ordsucc : set set var x:set var y:set hyp Subq x y hyp x = ordsucc y claim y iIn x -> y iIn y