Canonical Structure CompH_NT := Build_NT Ast_nt_law.Infix "o_NTh" := CompH_NT (at level 20, right associativity).

Lemma InterChange_law : (T o_NTh T') o_NTv U o_NTh U' =_NT (T o_NTv U) o_NTh T' o_NTv U'.