'Pitchfork t p = (prototerm_grafted p t).
definition prototerm_root: prototerm → prototerm ≝
- λt,q. ∃r. q●r ϵ t.
+ λt,q. ∃r. r ϵ t⋔q.
interpretation
"root (prototerm)"
'UpTriangle t = (prototerm_root t).
+(* Basic inversions *********************************************************)
+
+lemma prototerm_grafted_inv_gen (t) (p) (q):
+ q ϵ t⋔p → p●q ϵ t.
+// qed-.
+
(* Basic constructions ******************************************************)
lemma prototerm_in_comp_root (p) (t):