fact: Definition subst_var (E': context) (t': type) {E: context} {t: type} (v: var (E' ++ t' :: E) t) (b: term E t') : { c : term (E' ++ E) t | forall e, dterm c e = dvar v (unsubst_env E' t' E e (dterm b (proj_env E' E e))) }.
imports: Coq(Bool String List Program.Equality) CDF(Sequences)