(*notation ( output) "prop" ("#_" [1000] 1000) *)
notation ( output) "Trueprop" ("#_" [1000] 1000)

ML {*
  fun dest_cbinop t =
    let
      val (t2, rhs) = Thm.dest_comb t;
      val (bop, lhs) = Thm.dest_comb t2;
    in
      (bop, (lhs, rhs))
    end
*}

ML {*
  fun dest_ceq t =
    let
      val (bop, pair) = dest_cbinop t;
      val (bop_s, _) = Term.dest_Const (Thm.term_of bop);
    in
      if bop_s = "op =" then pair else (raise CTERM ("Not an equality", [t]))
    end
*}

ML {*
  fun split_binop_conv t =
    let
      val (lhs, rhs) = dest_ceq t;
      val (bop, _) = dest_cbinop lhs;
      val [clT, cr2] = bop |> Thm.ctyp_of_term |> Thm.dest_ctyp;
      val [cmT, crT] = Thm.dest_ctyp cr2;
    in
      Drule.instantiate' [SOME clT, SOME cmT, SOME crT] [NONE, NONE, NONE, NONE, SOME bop] @{thm arg_cong2}
    end
*}


ML {*
  fun split_arg_conv t =
    let
      val (lhs, rhs) = dest_ceq t;
      val (lop, larg) = Thm.dest_comb lhs;
      val [caT, crT] = lop |> Thm.ctyp_of_term |> Thm.dest_ctyp;
    in
      Drule.instantiate' [SOME caT, SOME crT] [NONE, NONE, SOME lop] @{thm arg_cong}
    end
*}

ML {*
  fun split_binop_tac n thm =
    let
      val concl = Thm.cprem_of thm n;
      val (_, cconcl) = Thm.dest_comb concl;
      val rewr = split_binop_conv cconcl;
    in
      rtac rewr n thm
    end
      handle CTERM _ => Seq.empty
*}


ML {*
  fun split_arg_tac n thm =
    let
      val concl = Thm.cprem_of thm n;
      val (_, cconcl) = Thm.dest_comb concl;
      val rewr = split_arg_conv cconcl;
    in
      rtac rewr n thm
    end
      handle CTERM _ => Seq.empty
*}


lemma trueprop_cong:
  shows "(a \<equiv> b) \<Longrightarrow> (Trueprop a \<equiv> Trueprop b)"
  by auto

lemma list_induct_hol4:
  fixes P :: "'a list \<Rightarrow> bool"
  assumes a: "((P []) \<and> (\<forall>t. (P t) \<longrightarrow> (\<forall>h. (P (h # t)))))"
  shows "\<forall>l. (P l)"
  using a
  apply (rule_tac allI)
  apply (induct_tac "l")
  apply (simp)
  apply (metis)
  done

ML {*
val no_vars = Thm.rule_attribute (fn context => fn th =>
  let
    val ctxt = Variable.set_body false (Context.proof_of context);
    val ((_, [th']), _) = Variable.import true [th] ctxt;
  in th' end);
*}

(*lemma equality_twice:
  "a = c \<Longrightarrow> b = d \<Longrightarrow> (a = b \<longrightarrow> c = d)"
by auto*)