# File nat_simprocs.ML

    (*  Title:      HOL/nat_simprocs.ML
        ID:         $Id: nat_simprocs.ML,v 1.33 2005/08/01 17:20:26 wenzelm Exp $
        Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
        Copyright   2000  University of Cambridge

    Simprocs for nat numerals.
    *)

    val Let_number_of = thm"Let_number_of";
    val Let_0 = thm"Let_0";
    val Let_1 = thm"Let_1";

    structure Nat_Numeral_Simprocs =
    struct

    (*Maps n to #n for n = 0, 1, 2*)
    val numeral_syms =
           [nat_numeral_0_eq_0 RS sym, nat_numeral_1_eq_1 RS sym, numeral_2_eq_2 RS sym];
    val numeral_sym_ss = HOL_ss addsimps numeral_syms;

    fun rename_numerals th =
        simplify numeral_sym_ss (Thm.transfer (the_context ()) th);

    (*Utilities*)

    fun mk_numeral n = HOLogic.number_of_const HOLogic.natT $ HOLogic.mk_bin n;

    (*Decodes a unary or binary numeral to a NATURAL NUMBER*)
    fun dest_numeral (Const ("0", _)) = 0
      | dest_numeral (Const ("Suc", _) $ t) = 1 + dest_numeral t
      | dest_numeral (Const("Numeral.number_of", _) $ w) =
          (IntInf.max (0, HOLogic.dest_binum w)
           handle TERM _ => raise TERM("Nat_Numeral_Simprocs.dest_numeral:1", [w]))
      | dest_numeral t = raise TERM("Nat_Numeral_Simprocs.dest_numeral:2", [t]);

    fun find_first_numeral past (t::terms) =
            ((dest_numeral t, t, rev past @ terms)
             handle TERM _ => find_first_numeral (t::past) terms)
      | find_first_numeral past [] = raise TERM("find_first_numeral", []);

    val zero = mk_numeral 0;
    val mk_plus = HOLogic.mk_binop "op +";

    (*Thus mk_sum[t] yields t+0; longer sums don't have a trailing zero*)
    fun mk_sum []        = zero
      | mk_sum [t,u]     = mk_plus (t, u)
      | mk_sum (t :: ts) = mk_plus (t, mk_sum ts);

    (*this version ALWAYS includes a trailing zero*)
    fun long_mk_sum []        = HOLogic.zero
      | long_mk_sum (t :: ts) = mk_plus (t, mk_sum ts);

    val dest_plus = HOLogic.dest_bin "op +" HOLogic.natT;

    (*extract the outer Sucs from a term and convert them to a binary numeral*)
    fun dest_Sucs (k, Const ("Suc", _) $ t) = dest_Sucs (k+1, t)
      | dest_Sucs (0, t) = t
      | dest_Sucs (k, t) = mk_plus (mk_numeral k, t);

    fun dest_sum t =
          let val (t,u) = dest_plus t
          in  dest_sum t @ dest_sum u  end
          handle TERM _ => [t];

    fun dest_Sucs_sum t = dest_sum (dest_Sucs (0,t));

    (** Other simproc items **)

    val trans_tac = Int_Numeral_Simprocs.trans_tac;

    val bin_simps =
         [nat_numeral_0_eq_0 RS sym, nat_numeral_1_eq_1 RS sym,
          add_nat_number_of, nat_number_of_add_left,
          diff_nat_number_of, le_number_of_eq_not_less,
          mult_nat_number_of, nat_number_of_mult_left,
          less_nat_number_of,
          Let_number_of, nat_number_of] @
         bin_arith_simps @ bin_rel_simps;

    fun prep_simproc (name, pats, proc) =
      Simplifier.simproc (Theory.sign_of (the_context ())) name pats proc;

    (*** CancelNumerals simprocs ***)

    val one = mk_numeral 1;
    val mk_times = HOLogic.mk_binop "op *";

    fun mk_prod [] = one
      | mk_prod [t] = t
      | mk_prod (t :: ts) = if t = one then mk_prod ts
                            else mk_times (t, mk_prod ts);

    val dest_times = HOLogic.dest_bin "op *" HOLogic.natT;

    fun dest_prod t =
          let val (t,u) = dest_times t
          in  dest_prod t @ dest_prod u  end
          handle TERM _ => [t];

    (*DON'T do the obvious simplifications; that would create special cases*)
    fun mk_coeff (k,t) = mk_times (mk_numeral k, t);

    (*Express t as a product of (possibly) a numeral with other factors, sorted*)
    fun dest_coeff t =
        let val ts = sort Term.term_ord (dest_prod t)
            val (n, _, ts') = find_first_numeral [] ts
                              handle TERM _ => (1, one, ts)
        in (n, mk_prod ts') end;

    (*Find first coefficient-term THAT MATCHES u*)
    fun find_first_coeff past u [] = raise TERM("find_first_coeff", [])
      | find_first_coeff past u (t::terms) =
            let val (n,u') = dest_coeff t
            in  if u aconv u' then (n, rev past @ terms)
                              else find_first_coeff (t::past) u terms
            end
            handle TERM _ => find_first_coeff (t::past) u terms;

    (*Simplify 1*n and n*1 to n*)
    val add_0s  = map rename_numerals [add_0, add_0_right];
    val mult_1s = map rename_numerals [thm"nat_mult_1", thm"nat_mult_1_right"];

    (*Final simplification: cancel + and *; replace Numeral0 by 0 and Numeral1 by 1*)

    (*And these help the simproc return False when appropriate, which helps
      the arith prover.*)
    val contra_rules = [add_Suc, add_Suc_right, Zero_not_Suc, Suc_not_Zero,
                        le_0_eq];

    val simplify_meta_eq =
        Int_Numeral_Simprocs.simplify_meta_eq
            ([nat_numeral_0_eq_0, numeral_1_eq_Suc_0, add_0, add_0_right,
              mult_0, mult_0_right, mult_1, mult_1_right] @ contra_rules);

    (** Restricted version of dest_Sucs_sum for nat_combine_numerals:
        Simprocs never apply unless the original expression contains at least one
        numeral in a coefficient position.
    **)

    fun ignore_Sucs (Const ("Suc", _) $ t) = ignore_Sucs t
      | ignore_Sucs t = t;

    fun is_numeral (Const("Numeral.number_of", _) $ w) = true
      | is_numeral _ = false;

    fun prod_has_numeral t = exists is_numeral (dest_prod t);

    fun restricted_dest_Sucs_sum t =
        if exists prod_has_numeral (dest_sum (ignore_Sucs t))
        then dest_Sucs_sum t
        else raise TERM("Nat_Numeral_Simprocs.restricted_dest_Sucs_sum", [t]);

    (*Like HOL_ss but with an ordering that brings numerals to the front
      under AC-rewriting.*)
    val num_ss = Int_Numeral_Simprocs.num_ss;

    (*** Applying CancelNumeralsFun ***)

    structure CancelNumeralsCommon =
      struct
      val mk_sum            = (fn T:typ => mk_sum)
      val dest_sum          = dest_Sucs_sum
      val mk_coeff          = mk_coeff
      val dest_coeff        = dest_coeff
      val find_first_coeff  = find_first_coeff []
      val trans_tac         = fn _ => trans_tac
      fun norm_tac ss =
        let val num_ss' = Simplifier.inherit_bounds ss num_ss in
          ALLGOALS (simp_tac (num_ss' addsimps numeral_syms @ add_0s @ mult_1s @
                                    [Suc_eq_add_numeral_1_left] @ add_ac))
          THEN ALLGOALS (simp_tac (num_ss' addsimps bin_simps @ add_ac @ mult_ac))
        end
      fun numeral_simp_tac ss =
        ALLGOALS (simp_tac (Simplifier.inherit_bounds ss HOL_ss addsimps add_0s @ bin_simps))
      val simplify_meta_eq  = simplify_meta_eq
      end;

    structure EqCancelNumerals = CancelNumeralsFun
     (open CancelNumeralsCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_eq
      val dest_bal = HOLogic.dest_bin "op =" HOLogic.natT
      val bal_add1 = nat_eq_add_iff1 RS trans
      val bal_add2 = nat_eq_add_iff2 RS trans
    );

    structure LessCancelNumerals = CancelNumeralsFun
     (open CancelNumeralsCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <"
      val dest_bal = HOLogic.dest_bin "op <" HOLogic.natT
      val bal_add1 = nat_less_add_iff1 RS trans
      val bal_add2 = nat_less_add_iff2 RS trans
    );

    structure LeCancelNumerals = CancelNumeralsFun
     (open CancelNumeralsCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <="
      val dest_bal = HOLogic.dest_bin "op <=" HOLogic.natT
      val bal_add1 = nat_le_add_iff1 RS trans
      val bal_add2 = nat_le_add_iff2 RS trans
    );

    structure DiffCancelNumerals = CancelNumeralsFun
     (open CancelNumeralsCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binop "op -"
      val dest_bal = HOLogic.dest_bin "op -" HOLogic.natT
      val bal_add1 = nat_diff_add_eq1 RS trans
      val bal_add2 = nat_diff_add_eq2 RS trans
    );

    val cancel_numerals =
      map prep_simproc
       [("nateq_cancel_numerals",
         ["(l::nat) + m = n", "(l::nat) = m + n",
          "(l::nat) * m = n", "(l::nat) = m * n",
          "Suc m = n", "m = Suc n"],
         EqCancelNumerals.proc),
        ("natless_cancel_numerals",
         ["(l::nat) + m < n", "(l::nat) < m + n",
          "(l::nat) * m < n", "(l::nat) < m * n",
          "Suc m < n", "m < Suc n"],
         LessCancelNumerals.proc),
        ("natle_cancel_numerals",
         ["(l::nat) + m <= n", "(l::nat) <= m + n",
          "(l::nat) * m <= n", "(l::nat) <= m * n",
          "Suc m <= n", "m <= Suc n"],
         LeCancelNumerals.proc),
        ("natdiff_cancel_numerals",
         ["((l::nat) + m) - n", "(l::nat) - (m + n)",
          "(l::nat) * m - n", "(l::nat) - m * n",
          "Suc m - n", "m - Suc n"],
         DiffCancelNumerals.proc)];

    (*** Applying CombineNumeralsFun ***)

    structure CombineNumeralsData =
      struct
      val add               = IntInf.+
      val mk_sum            = (fn T:typ => long_mk_sum)  (*to work for 2*x + 3*x *)
      val dest_sum          = restricted_dest_Sucs_sum
      val mk_coeff          = mk_coeff
      val dest_coeff        = dest_coeff
      val left_distrib      = left_add_mult_distrib RS trans
      val prove_conv        = Bin_Simprocs.prove_conv_nohyps
      val trans_tac         = fn _ => trans_tac
      fun norm_tac ss =
        let val num_ss' = Simplifier.inherit_bounds ss num_ss in
          ALLGOALS (simp_tac (num_ss' addsimps numeral_syms @ add_0s @ mult_1s @
                                  [Suc_eq_add_numeral_1] @ add_ac))
          THEN ALLGOALS (simp_tac (num_ss' addsimps bin_simps @ add_ac @ mult_ac))
        end
      fun numeral_simp_tac ss =
        ALLGOALS (simp_tac (Simplifier.inherit_bounds ss HOL_ss addsimps add_0s @ bin_simps))
      val simplify_meta_eq  = simplify_meta_eq
      end;

    structure CombineNumerals = CombineNumeralsFun(CombineNumeralsData);

    val combine_numerals =
      prep_simproc ("nat_combine_numerals", ["(i::nat) + j", "Suc (i + j)"], CombineNumerals.proc);

    (*** Applying CancelNumeralFactorFun ***)

    structure CancelNumeralFactorCommon =
      struct
      val mk_coeff          = mk_coeff
      val dest_coeff        = dest_coeff
      val trans_tac         = fn _ => trans_tac
      fun norm_tac ss =
        let val num_ss' = Simplifier.inherit_bounds ss num_ss in
          ALLGOALS (simp_tac (num_ss' addsimps numeral_syms @ add_0s @ mult_1s @
                                    [Suc_eq_add_numeral_1_left] @ add_ac))
          THEN ALLGOALS (simp_tac (num_ss' addsimps bin_simps @ add_ac @ mult_ac))
        end
      fun numeral_simp_tac ss =
        ALLGOALS (simp_tac (Simplifier.inherit_bounds ss HOL_ss addsimps bin_simps))
      val simplify_meta_eq  = simplify_meta_eq
      end

    structure DivCancelNumeralFactor = CancelNumeralFactorFun
     (open CancelNumeralFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binop "Divides.op div"
      val dest_bal = HOLogic.dest_bin "Divides.op div" HOLogic.natT
      val cancel = nat_mult_div_cancel1 RS trans
      val neg_exchanges = false
    )

    structure EqCancelNumeralFactor = CancelNumeralFactorFun
     (open CancelNumeralFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_eq
      val dest_bal = HOLogic.dest_bin "op =" HOLogic.natT
      val cancel = nat_mult_eq_cancel1 RS trans
      val neg_exchanges = false
    )

    structure LessCancelNumeralFactor = CancelNumeralFactorFun
     (open CancelNumeralFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <"
      val dest_bal = HOLogic.dest_bin "op <" HOLogic.natT
      val cancel = nat_mult_less_cancel1 RS trans
      val neg_exchanges = true
    )

    structure LeCancelNumeralFactor = CancelNumeralFactorFun
     (open CancelNumeralFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <="
      val dest_bal = HOLogic.dest_bin "op <=" HOLogic.natT
      val cancel = nat_mult_le_cancel1 RS trans
      val neg_exchanges = true
    )

    val cancel_numeral_factors =
      map prep_simproc
       [("nateq_cancel_numeral_factors",
         ["(l::nat) * m = n", "(l::nat) = m * n"],
         EqCancelNumeralFactor.proc),
        ("natless_cancel_numeral_factors",
         ["(l::nat) * m < n", "(l::nat) < m * n"],
         LessCancelNumeralFactor.proc),
        ("natle_cancel_numeral_factors",
         ["(l::nat) * m <= n", "(l::nat) <= m * n"],
         LeCancelNumeralFactor.proc),
        ("natdiv_cancel_numeral_factors",
         ["((l::nat) * m) div n", "(l::nat) div (m * n)"],
         DivCancelNumeralFactor.proc)];

    (*** Applying ExtractCommonTermFun ***)

    (*this version ALWAYS includes a trailing one*)
    fun long_mk_prod []        = one
      | long_mk_prod (t :: ts) = mk_times (t, mk_prod ts);

    (*Find first term that matches u*)
    fun find_first past u []         = raise TERM("find_first", [])
      | find_first past u (t::terms) =
            if u aconv t then (rev past @ terms)
            else find_first (t::past) u terms
            handle TERM _ => find_first (t::past) u terms;

    (** Final simplification for the CancelFactor simprocs **)
    val simplify_one =
        Int_Numeral_Simprocs.simplify_meta_eq
           [mult_1_left, mult_1_right, div_1, numeral_1_eq_Suc_0];

    fun cancel_simplify_meta_eq cancel_th ss th =
        simplify_one ss (([th, cancel_th]) MRS trans);

    structure CancelFactorCommon =
      struct
      val mk_sum            = (fn T:typ => long_mk_prod)
      val dest_sum          = dest_prod
      val mk_coeff          = mk_coeff
      val dest_coeff        = dest_coeff
      val find_first        = find_first []
      val trans_tac         = fn _ => trans_tac
      fun norm_tac ss =
        ALLGOALS (simp_tac (Simplifier.inherit_bounds ss HOL_ss addsimps mult_1s @ mult_ac))
      end;

    structure EqCancelFactor = ExtractCommonTermFun
     (open CancelFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_eq
      val dest_bal = HOLogic.dest_bin "op =" HOLogic.natT
      val simplify_meta_eq  = cancel_simplify_meta_eq nat_mult_eq_cancel_disj
    );

    structure LessCancelFactor = ExtractCommonTermFun
     (open CancelFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <"
      val dest_bal = HOLogic.dest_bin "op <" HOLogic.natT
      val simplify_meta_eq  = cancel_simplify_meta_eq nat_mult_less_cancel_disj
    );

    structure LeCancelFactor = ExtractCommonTermFun
     (open CancelFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binrel "op <="
      val dest_bal = HOLogic.dest_bin "op <=" HOLogic.natT
      val simplify_meta_eq  = cancel_simplify_meta_eq nat_mult_le_cancel_disj
    );

    structure DivideCancelFactor = ExtractCommonTermFun
     (open CancelFactorCommon
      val prove_conv = Bin_Simprocs.prove_conv
      val mk_bal   = HOLogic.mk_binop "Divides.op div"
      val dest_bal = HOLogic.dest_bin "Divides.op div" HOLogic.natT
      val simplify_meta_eq  = cancel_simplify_meta_eq nat_mult_div_cancel_disj
    );

    val cancel_factor =
      map prep_simproc
       [("nat_eq_cancel_factor",
         ["(l::nat) * m = n", "(l::nat) = m * n"],
         EqCancelFactor.proc),
        ("nat_less_cancel_factor",
         ["(l::nat) * m < n", "(l::nat) < m * n"],
         LessCancelFactor.proc),
        ("nat_le_cancel_factor",
         ["(l::nat) * m <= n", "(l::nat) <= m * n"],
         LeCancelFactor.proc),
        ("nat_divide_cancel_factor",
         ["((l::nat) * m) div n", "(l::nat) div (m * n)"],
         DivideCancelFactor.proc)];

    end;

    Addsimprocs Nat_Numeral_Simprocs.cancel_numerals;
    Addsimprocs [Nat_Numeral_Simprocs.combine_numerals];
    Addsimprocs Nat_Numeral_Simprocs.cancel_numeral_factors;
    Addsimprocs Nat_Numeral_Simprocs.cancel_factor;

    (*examples:
    print_depth 22;
    set timing;
    set trace_simp;
    fun test s = (Goal s; by (Simp_tac 1));

    (*cancel_numerals*)
    test "l +( 2) + (2) + 2 + (l + 2) + (oo  + 2) = (uu::nat)";
    test "(2*length xs < 2*length xs + j)";
    test "(2*length xs < length xs * 2 + j)";
    test "2*u = (u::nat)";
    test "2*u = Suc (u)";
    test "(i + j + 12 + (k::nat)) - 15 = y";
    test "(i + j + 12 + (k::nat)) - 5 = y";
    test "Suc u - 2 = y";
    test "Suc (Suc (Suc u)) - 2 = y";
    test "(i + j + 2 + (k::nat)) - 1 = y";
    test "(i + j + 1 + (k::nat)) - 2 = y";

    test "(2*x + (u*v) + y) - v*3*u = (w::nat)";
    test "(2*x*u*v + 5 + (u*v)*4 + y) - v*u*4 = (w::nat)";
    test "(2*x*u*v + (u*v)*4 + y) - v*u = (w::nat)";
    test "Suc (Suc (2*x*u*v + u*4 + y)) - u = w";
    test "Suc ((u*v)*4) - v*3*u = w";
    test "Suc (Suc ((u*v)*3)) - v*3*u = w";

    test "(i + j + 12 + (k::nat)) = u + 15 + y";
    test "(i + j + 32 + (k::nat)) - (u + 15 + y) = zz";
    test "(i + j + 12 + (k::nat)) = u + 5 + y";
    (*Suc*)
    test "(i + j + 12 + k) = Suc (u + y)";
    test "Suc (Suc (Suc (Suc (Suc (u + y))))) <= ((i + j) + 41 + k)";
    test "(i + j + 5 + k) < Suc (Suc (Suc (Suc (Suc (u + y)))))";
    test "Suc (Suc (Suc (Suc (Suc (u + y))))) - 5 = v";
    test "(i + j + 5 + k) = Suc (Suc (Suc (Suc (Suc (Suc (Suc (u + y)))))))";
    test "2*y + 3*z + 2*u = Suc (u)";
    test "2*y + 3*z + 6*w + 2*y + 3*z + 2*u = Suc (u)";
    test "2*y + 3*z + 6*w + 2*y + 3*z + 2*u = 2*y' + 3*z' + 6*w' + 2*y' + 3*z' + u + (vv::nat)";
    test "6 + 2*y + 3*z + 4*u = Suc (vv + 2*u + z)";
    test "(2*n*m) < (3*(m*n)) + (u::nat)";

    test "(Suc (Suc (Suc (Suc (Suc (Suc (case length (f c) of 0 => 0 | Suc k => k)))))) <= Suc 0)";

    test "Suc (Suc (Suc (Suc (Suc (Suc (length l1 + length l2)))))) <= length l1";

    test "( (Suc (Suc (Suc (Suc (Suc (length (compT P E A ST mxr e) + length l3)))))) <= length (compT P E A ST mxr e))";

    test "( (Suc (Suc (Suc (Suc (Suc (length (compT P E A ST mxr e) + length (compT P E (A Un \<A> e) ST mxr c))))))) <= length (compT P E A ST mxr e))";

    (*negative numerals: FAIL*)
    test "(i + j + -23 + (k::nat)) < u + 15 + y";
    test "(i + j + 3 + (k::nat)) < u + -15 + y";
    test "(i + j + -12 + (k::nat)) - 15 = y";
    test "(i + j + 12 + (k::nat)) - -15 = y";
    test "(i + j + -12 + (k::nat)) - -15 = y";

    (*combine_numerals*)
    test "k + 3*k = (u::nat)";
    test "Suc (i + 3) = u";
    test "Suc (i + j + 3 + k) = u";
    test "k + j + 3*k + j = (u::nat)";
    test "Suc (j*i + i + k + 5 + 3*k + i*j*4) = (u::nat)";
    test "(2*n*m) + (3*(m*n)) = (u::nat)";
    (*negative numerals: FAIL*)
    test "Suc (i + j + -3 + k) = u";

    (*cancel_numeral_factors*)
    test "9*x = 12 * (y::nat)";
    test "(9*x) div (12 * (y::nat)) = z";
    test "9*x < 12 * (y::nat)";
    test "9*x <= 12 * (y::nat)";

    (*cancel_factor*)
    test "x*k = k*(y::nat)";
    test "k = k*(y::nat)";
    test "a*(b*c) = (b::nat)";
    test "a*(b*c) = d*(b::nat)*(x*a)";

    test "x*k < k*(y::nat)";
    test "k < k*(y::nat)";
    test "a*(b*c) < (b::nat)";
    test "a*(b*c) < d*(b::nat)*(x*a)";

    test "x*k <= k*(y::nat)";
    test "k <= k*(y::nat)";
    test "a*(b*c) <= (b::nat)";
    test "a*(b*c) <= d*(b::nat)*(x*a)";

    test "(x*k) div (k*(y::nat)) = (uu::nat)";
    test "(k) div (k*(y::nat)) = (uu::nat)";
    test "(a*(b*c)) div ((b::nat)) = (uu::nat)";
    test "(a*(b*c)) div (d*(b::nat)*(x*a)) = (uu::nat)";
    *)

    (*** Prepare linear arithmetic for nat numerals ***)

    local

    (* reduce contradictory <= to False *)
    val add_rules =
      [thm "Let_number_of", Let_0, Let_1, nat_0, nat_1,
       add_nat_number_of, diff_nat_number_of, mult_nat_number_of,
       eq_nat_number_of, less_nat_number_of, le_number_of_eq_not_less,
       le_Suc_number_of,le_number_of_Suc,
       less_Suc_number_of,less_number_of_Suc,
       Suc_eq_number_of,eq_number_of_Suc,
       mult_Suc, mult_Suc_right,
       eq_number_of_0, eq_0_number_of, less_0_number_of,
       of_int_number_of_eq, of_nat_number_of_eq, nat_number_of, if_True, if_False];

    val simprocs = [Nat_Numeral_Simprocs.combine_numerals]@
                    Nat_Numeral_Simprocs.cancel_numerals;

    in

    val nat_simprocs_setup =
     [Fast_Arith.map_data (fn {add_mono_thms, mult_mono_thms, inj_thms, lessD, neqE, simpset} =>
       {add_mono_thms = add_mono_thms, mult_mono_thms = mult_mono_thms,
        inj_thms = inj_thms, lessD = lessD, neqE = neqE,
        simpset = simpset addsimps add_rules
                          addsimprocs simprocs})];

    end;