fact: Definition nds_fixpt_eq f := forall n, natp n -> \2c <=c n -> f n = \csup (fun_image (Zo Nat (fun k => \0c <c k /\ k <c n )) (fun k => (ndsC k) *c (f (n -c k)))).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)