fact: Definition subst_abs {L : lambda_calculus_data} {m n} l (f : stn m → L n) : subst (abs l) f = abs (subst l (extend_tuple (λ i, inflate (f i)) (var (stnweq (inr tt))))) := pr12 (pr222 (pr222 L)) m n l f.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.StandardFiniteSets UniMath.Combinatorics.Tuples