Section AssocTheorems.
Context {e: expr}
{Mono: Monotonicity L Gamma prodp}
{Assoc: Associativity L Gamma prodp}.
Context {LU: LeftUnit L Gamma e prodp}
{RU: RightUnit L Gamma e prodp}.

Lemma assoc_fold_left_fold_right_equiv: forall xs,
|-- fold_left prodp xs e <--> fold_right prodp e xs.