fact: Fixpoint ptree_merge_pairs (p1 : ptree) (l : list ptree) : ptree := match l with | nil => p1 | p2 :: nil => ptree_meld p1 p2 | p2 :: p3 :: l' => ptree_meld (ptree_meld p1 p2) (ptree_merge_pairs p3 l') end.
imports: Coq(List Arith ZArith Psatz) mathcomp.ssreflect(ssrfun ssrbool fintype)