stackInSomeState : {l m : Level } {D : Set l} {t : Set m } (s : SingleLinkedStack D ) -> Stack {l} {m} D {t}  ( SingleLinkedStack  D )
stackInSomeState s =  record { stack = s ; stackMethods = singleLinkedStackSpec }

push->push->pop2 : {l : Level } {D : Set l} (x y : D ) (s : SingleLinkedStack D ) ->
pushStack ( stackInSomeState s )  x ( \s1 -> pushStack s1 y ( \s2 -> pop2Stack s2 ( \s3 y1 x1 -> (Just x ≡ x1 ) ∧ (Just y ≡ y1 ) ) ))
push->push->pop2 {l} {D} x y s = record { pi1 = refl ; pi2 = refl }