fact: Fixpoint find_just_one_aux (n : state) (g : grid) (st : state) : jRes := if st is (_, p, bs) :: st1 then if n is _ :: n1 then try_just_one (behead bs) p 1 g st1 (find_just_one_aux n1) else jNone else jOne g.
imports: mathcomp(all_ssreflect) mathcomp(zify)