Section Coinc_refl.
Context {AR : Arity}.
Definition pick_variety_auxCP {m : nat} (s : SS.elt) (cp : cartesianPower positive (S (S m))) : bool.
Definition pick_variety (s : SS.elt) (st : STt) :=
STexists_ (fun t => pick_variety_aux s t) st.
Definition exists_witness (f : SS.elt -> bool) (s : SS.t) : option SS.elt :=
SS.choose (SS.filter f s).
Definition pick_varieties_aux (s1 : SS.elt) (ss : SS.t) (st : STt)
: (option (SS.elt * SS.elt)) :=
match ((exists_witness (fun s2 => let i := S.inter s1 s2 in
pick_variety i st)) ss) with
| None => None
| Some s2 => Some(s1,s2)
end.
Definition pick_varieties (ss : SS.t) (st : STt)
: (option (SS.elt * SS.elt)) :=
match (exists_witness (fun s =>
match (pick_varieties_aux s (SS.remove s ss) st) with
| None => false
| _ => true
end) ss) with
| None => None
| Some s1 => pick_varieties_aux s1 (SS.remove s1 ss) st
end.
Definition eqop (p1 p2 : option SS.elt) :=
match p1,p2 with
| None, None => True
| Some s1, Some s2 => True
| _, _ => False
end.
Definition eqopp (p1 p2 : option (SS.elt * SS.elt)) :=
match p1,p2 with
| None, None => True
| Some s1, Some s2 => True
| _, _ => False
end.

Lemma pick_varieties_ok_1 : forall s1 s2 ss st,
pick_varieties ss st = Some(s1,s2) ->
SS.In s1 ss.