lte Cons x' xs' Cons x xs lte xs' xs lte Cons x xs Nil False even Cons x Nil False even Cons x' Cons x xs even xs notEmpty Cons x xs True notEmpty Nil False lte Nil y True even Nil True goal x y and lte x y even x and False False False and True False False and False True False and True True True even 1 lte 2 True 0 Cons 2 Nil 0 notEmpty 1 and 2 goal 2 False 0 INNERMOST