fact: Definition σ (i: bool) (p: list constraint) : term := fold_right (fun '((a, x), (y, b)) s => arr (ρ i a b x y) s) (atom (to_nat (0, 4))) p.
imports: List Undecidability.SemiUnification.SemiU Undecidability.SemiUnification.Util(Enumerable) ssreflect ssrfun ssrbool