File arith_data.ML (Isabelle2005: October 2005)

# File arith_data.ML

    (*  Title:      HOL/arith_data.ML
        ID:         $Id: arith_data.ML,v 1.73 2005/09/23 20:21:51 wenzelm Exp $
        Author:     Markus Wenzel, Stefan Berghofer and Tobias Nipkow

    Various arithmetic proof procedures.
    *)

    (*---------------------------------------------------------------------------*)
    (* 1. Cancellation of common terms                                           *)
    (*---------------------------------------------------------------------------*)

    structure NatArithUtils =
    struct

    (** abstract syntax of structure nat: 0, Suc, + **)

    (* mk_sum, mk_norm_sum *)

    val one = HOLogic.mk_nat 1;
    val mk_plus = HOLogic.mk_binop "op +";

    fun mk_sum [] = HOLogic.zero
      | mk_sum [t] = t
      | mk_sum (t :: ts) = mk_plus (t, mk_sum ts);

    (*normal form of sums: Suc (... (Suc (a + (b + ...))))*)
    fun mk_norm_sum ts =
      let val (ones, sums) = List.partition (equal one) ts in
        funpow (length ones) HOLogic.mk_Suc (mk_sum sums)
      end;

    (* dest_sum *)

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

    fun dest_sum tm =
      if HOLogic.is_zero tm then []
      else
        (case try HOLogic.dest_Suc tm of
          SOME t => one :: dest_sum t
        | NONE =>
            (case try dest_plus tm of
              SOME (t, u) => dest_sum t @ dest_sum u
            | NONE => [tm]));

    (** generic proof tools **)

    (* prove conversions *)

    val mk_eqv = HOLogic.mk_Trueprop o HOLogic.mk_eq;

    fun prove_conv expand_tac norm_tac sg ss tu =
      mk_meta_eq (prove_goalw_cterm_nocheck [] (cterm_of sg (mk_eqv tu))
        (K [expand_tac, norm_tac ss]))
      handle ERROR => error ("The error(s) above occurred while trying to prove " ^
        (string_of_cterm (cterm_of sg (mk_eqv tu))));

    val subst_equals = prove_goal HOL.thy "[| t = s; u = t |] ==> u = s"
      (fn prems => [cut_facts_tac prems 1, SIMPSET' asm_simp_tac 1]);

    (* rewriting *)

    fun simp_all_tac rules ss =
      ALLGOALS (simp_tac (Simplifier.inherit_bounds ss HOL_ss addsimps rules));

    val add_rules = [add_Suc, add_Suc_right, add_0, add_0_right];
    val mult_rules = [mult_Suc, mult_Suc_right, mult_0, mult_0_right];

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

    end;

    signature ARITH_DATA =
    sig
      val nat_cancel_sums_add: simproc list
      val nat_cancel_sums: simproc list
    end;

    structure ArithData: ARITH_DATA =
    struct

    open NatArithUtils;

    (** cancel common summands **)

    structure Sum =
    struct
      val mk_sum = mk_norm_sum;
      val dest_sum = dest_sum;
      val prove_conv = prove_conv;
      fun norm_tac ss = simp_all_tac add_rules ss THEN simp_all_tac add_ac ss;
    end;

    fun gen_uncancel_tac rule ct =
      rtac (instantiate' [] [NONE, SOME ct] (rule RS subst_equals)) 1;

    (* nat eq *)

    structure EqCancelSums = CancelSumsFun
    (struct
      open Sum;
      val mk_bal = HOLogic.mk_eq;
      val dest_bal = HOLogic.dest_bin "op =" HOLogic.natT;
      val uncancel_tac = gen_uncancel_tac nat_add_left_cancel;
    end);

    (* nat less *)

    structure LessCancelSums = CancelSumsFun
    (struct
      open Sum;
      val mk_bal = HOLogic.mk_binrel "op <";
      val dest_bal = HOLogic.dest_bin "op <" HOLogic.natT;
      val uncancel_tac = gen_uncancel_tac nat_add_left_cancel_less;
    end);

    (* nat le *)

    structure LeCancelSums = CancelSumsFun
    (struct
      open Sum;
      val mk_bal = HOLogic.mk_binrel "op <=";
      val dest_bal = HOLogic.dest_bin "op <=" HOLogic.natT;
      val uncancel_tac = gen_uncancel_tac nat_add_left_cancel_le;
    end);

    (* nat diff *)

    structure DiffCancelSums = CancelSumsFun
    (struct
      open Sum;
      val mk_bal = HOLogic.mk_binop "op -";
      val dest_bal = HOLogic.dest_bin "op -" HOLogic.natT;
      val uncancel_tac = gen_uncancel_tac diff_cancel;
    end);

    (** prepare nat_cancel simprocs **)

    val nat_cancel_sums_add = map prep_simproc
      [("nateq_cancel_sums",
         ["(l::nat) + m = n", "(l::nat) = m + n", "Suc m = n", "m = Suc n"], EqCancelSums.proc),
       ("natless_cancel_sums",
         ["(l::nat) + m < n", "(l::nat) < m + n", "Suc m < n", "m < Suc n"], LessCancelSums.proc),
       ("natle_cancel_sums",
         ["(l::nat) + m <= n", "(l::nat) <= m + n", "Suc m <= n", "m <= Suc n"], LeCancelSums.proc)];

    val nat_cancel_sums = nat_cancel_sums_add @
      [prep_simproc ("natdiff_cancel_sums",
        ["((l::nat) + m) - n", "(l::nat) - (m + n)", "Suc m - n", "m - Suc n"], DiffCancelSums.proc)];

    end;

    open ArithData;

    (*---------------------------------------------------------------------------*)
    (* 2. Linear arithmetic                                                      *)
    (*---------------------------------------------------------------------------*)

    (* Parameters data for general linear arithmetic functor *)

    structure LA_Logic: LIN_ARITH_LOGIC =
    struct
    val ccontr = ccontr;
    val conjI = conjI;
    val notI = notI;
    val sym = sym;
    val not_lessD = linorder_not_less RS iffD1;
    val not_leD = linorder_not_le RS iffD1;

    fun mk_Eq thm = (thm RS Eq_FalseI) handle THM _ => (thm RS Eq_TrueI);

    val mk_Trueprop = HOLogic.mk_Trueprop;

    fun atomize thm = case #prop(rep_thm thm) of
        Const("Trueprop",_) $ (Const("op &",_) $ _ $ _) =>
        atomize(thm RS conjunct1) @ atomize(thm RS conjunct2)
      | _ => [thm];

    fun neg_prop(TP$(Const("Not",_)$t)) = TP$t
      | neg_prop(TP$t) = TP $ (Const("Not",HOLogic.boolT-->HOLogic.boolT)$t);

    fun is_False thm =
      let val _ $ t = #prop(rep_thm thm)
      in t = Const("False",HOLogic.boolT) end;

    fun is_nat(t) = fastype_of1 t = HOLogic.natT;

    fun mk_nat_thm sg t =
      let val ct = cterm_of sg t  and cn = cterm_of sg (Var(("n",0),HOLogic.natT))
      in instantiate ([],[(cn,ct)]) le0 end;

    end;

    (* arith theory data *)

    structure ArithTheoryData = TheoryDataFun
    (struct
      val name = "HOL/arith";
      type T = {splits: thm list, inj_consts: (string * typ)list, discrete: string  list, presburger: (int -> tactic) option};

      val empty = {splits = [], inj_consts = [], discrete = [], presburger = NONE};
      val copy = I;
      val extend = I;
      fun merge _ ({splits= splits1, inj_consts= inj_consts1, discrete= discrete1, presburger= presburger1},
                 {splits= splits2, inj_consts= inj_consts2, discrete= discrete2, presburger= presburger2}) =
       {splits = Drule.merge_rules (splits1, splits2),
        inj_consts = merge_lists inj_consts1 inj_consts2,
        discrete = merge_lists discrete1 discrete2,
        presburger = (case presburger1 of NONE => presburger2 | p => p)};
      fun print _ _ = ();
    end);

    fun arith_split_add (thy, thm) = (ArithTheoryData.map (fn {splits,inj_consts,discrete,presburger} =>
      {splits= thm::splits, inj_consts= inj_consts, discrete= discrete, presburger= presburger}) thy, thm);

    fun arith_discrete d = ArithTheoryData.map (fn {splits,inj_consts,discrete,presburger} =>
      {splits = splits, inj_consts = inj_consts, discrete = d :: discrete, presburger= presburger});

    fun arith_inj_const c = ArithTheoryData.map (fn {splits,inj_consts,discrete,presburger} =>
      {splits = splits, inj_consts = c :: inj_consts, discrete = discrete, presburger = presburger});

    structure LA_Data_Ref: LIN_ARITH_DATA =
    struct

    (* Decomposition of terms *)

    fun nT (Type("fun",[N,_])) = N = HOLogic.natT
      | nT _ = false;

    fun add_atom(t,m,(p,i)) = (case AList.lookup (op =) p t of NONE => ((t, m) :: p, i)
                               | SOME n => (AList.update (op =) (t, ratadd (n, m)) p, i));

    exception Zero;

    fun rat_of_term(numt,dent) =
      let val num = HOLogic.dest_binum numt and den = HOLogic.dest_binum dent
      in if den = 0 then raise Zero else int_ratdiv(num,den) end;

    (* Warning: in rare cases number_of encloses a non-numeral,
       in which case dest_binum raises TERM; hence all the handles below.
       Same for Suc-terms that turn out not to be numerals -
       although the simplifier should eliminate those anyway...
    *)

    fun number_of_Sucs (Const("Suc",_) $ n) = number_of_Sucs n + 1
      | number_of_Sucs t = if HOLogic.is_zero t then 0
                           else raise TERM("number_of_Sucs",[])

    (* decompose nested multiplications, bracketing them to the right and combining all
       their coefficients
    *)

    fun demult inj_consts =
    let
    fun demult((mC as Const("op *",_)) $ s $ t,m) = ((case s of
            Const("Numeral.number_of",_)$n
            => demult(t,ratmul(m,rat_of_intinf(HOLogic.dest_binum n)))
          | Const("uminus",_)$(Const("Numeral.number_of",_)$n)
            => demult(t,ratmul(m,rat_of_intinf(~(HOLogic.dest_binum n))))
          | Const("Suc",_) $ _
            => demult(t,ratmul(m,rat_of_int(number_of_Sucs s)))
          | Const("op *",_) $ s1 $ s2 => demult(mC $ s1 $ (mC $ s2 $ t),m)
          | Const("HOL.divide",_) $ numt $ (Const("Numeral.number_of",_)$dent) =>
              let val den = HOLogic.dest_binum dent
              in if den = 0 then raise Zero
                 else demult(mC $ numt $ t,ratmul(m, ratinv(rat_of_intinf den)))
              end
          | _ => atomult(mC,s,t,m)
          ) handle TERM _ => atomult(mC,s,t,m))
      | demult(atom as Const("HOL.divide",_) $ t $ (Const("Numeral.number_of",_)$dent), m) =
          (let val den = HOLogic.dest_binum dent
           in if den = 0 then raise Zero else demult(t,ratmul(m, ratinv(rat_of_intinf den))) end
           handle TERM _ => (SOME atom,m))
      | demult(Const("0",_),m) = (NONE, rat_of_int 0)
      | demult(Const("1",_),m) = (NONE, m)
      | demult(t as Const("Numeral.number_of",_)$n,m) =
          ((NONE,ratmul(m,rat_of_intinf(HOLogic.dest_binum n)))
           handle TERM _ => (SOME t,m))
      | demult(Const("uminus",_)$t, m) = demult(t,ratmul(m,rat_of_int(~1)))
      | demult(t as Const f $ x, m) =
          (if f mem inj_consts then SOME x else SOME t,m)
      | demult(atom,m) = (SOME atom,m)

    and atomult(mC,atom,t,m) = (case demult(t,m) of (NONE,m') => (SOME atom,m')
                                | (SOME t',m') => (SOME(mC $ atom $ t'),m'))
    in demult end;

    fun decomp2 inj_consts (rel,lhs,rhs) =
    let
    (* Turn term into list of summand * multiplicity plus a constant *)
    fun poly(Const("op +",_) $ s $ t, m, pi) = poly(s,m,poly(t,m,pi))
      | poly(all as Const("op -",T) $ s $ t, m, pi) =
          if nT T then add_atom(all,m,pi) else poly(s,m,poly(t,ratneg m,pi))
      | poly(all as Const("uminus",T) $ t, m, pi) =
          if nT T then add_atom(all,m,pi) else poly(t,ratneg m,pi)
      | poly(Const("0",_), _, pi) = pi
      | poly(Const("1",_), m, (p,i)) = (p,ratadd(i,m))
      | poly(Const("Suc",_)$t, m, (p,i)) = poly(t, m, (p,ratadd(i,m)))
      | poly(t as Const("op *",_) $ _ $ _, m, pi as (p,i)) =
          (case demult inj_consts (t,m) of
             (NONE,m') => (p,ratadd(i,m))
           | (SOME u,m') => add_atom(u,m',pi))
      | poly(t as Const("HOL.divide",_) $ _ $ _, m, pi as (p,i)) =
          (case demult inj_consts (t,m) of
             (NONE,m') => (p,ratadd(i,m'))
           | (SOME u,m') => add_atom(u,m',pi))
      | poly(all as (Const("Numeral.number_of",_)$t,m,(p,i))) =
          ((p,ratadd(i,ratmul(m,rat_of_intinf(HOLogic.dest_binum t))))
           handle TERM _ => add_atom all)
      | poly(all as Const f $ x, m, pi) =
          if f mem inj_consts then poly(x,m,pi) else add_atom(all,m,pi)
      | poly x  = add_atom x;

    val (p,i) = poly(lhs,rat_of_int 1,([],rat_of_int 0))
    and (q,j) = poly(rhs,rat_of_int 1,([],rat_of_int 0))

      in case rel of
           "op <"  => SOME(p,i,"<",q,j)
         | "op <=" => SOME(p,i,"<=",q,j)
         | "op ="  => SOME(p,i,"=",q,j)
         | _       => NONE
      end handle Zero => NONE;

    fun negate(SOME(x,i,rel,y,j,d)) = SOME(x,i,"~"^rel,y,j,d)
      | negate NONE = NONE;

    fun of_lin_arith_sort sg U =
      Type.of_sort (Sign.tsig_of sg) (U,["Ring_and_Field.ordered_idom"])

    fun allows_lin_arith sg discrete (U as Type(D,[])) =
          if of_lin_arith_sort sg U
          then (true, D mem discrete)
          else (* special cases *)
               if D mem discrete then (true,true) else (false,false)
      | allows_lin_arith sg discrete U = (of_lin_arith_sort sg U, false);

    fun decomp1 (sg,discrete,inj_consts) (T,xxx) =
      (case T of
         Type("fun",[U,_]) =>
           (case allows_lin_arith sg discrete U of
              (true,d) => (case decomp2 inj_consts xxx of NONE => NONE
                           | SOME(p,i,rel,q,j) => SOME(p,i,rel,q,j,d))
            | (false,_) => NONE)
       | _ => NONE);

    fun decomp2 data (_$(Const(rel,T)$lhs$rhs)) = decomp1 data (T,(rel,lhs,rhs))
      | decomp2 data (_$(Const("Not",_)$(Const(rel,T)$lhs$rhs))) =
          negate(decomp1 data (T,(rel,lhs,rhs)))
      | decomp2 data _ = NONE

    fun decomp sg =
      let val {discrete, inj_consts, ...} = ArithTheoryData.get sg
      in decomp2 (sg,discrete,inj_consts) end

    fun number_of(n,T) = HOLogic.number_of_const T $ (HOLogic.mk_bin n)

    end;

    structure Fast_Arith =
      Fast_Lin_Arith(structure LA_Logic=LA_Logic and LA_Data=LA_Data_Ref);

    val fast_arith_tac    = Fast_Arith.lin_arith_tac false
    and fast_ex_arith_tac = Fast_Arith.lin_arith_tac
    and trace_arith    = Fast_Arith.trace
    and fast_arith_neq_limit = Fast_Arith.fast_arith_neq_limit;

    local

    val isolateSuc =
      let val thy = theory "Nat"
      in prove_goal thy "Suc(i+j) = i+j + Suc 0"
         (fn _ => [simp_tac (simpset_of thy) 1])
      end;

    (* reduce contradictory <= to False.
       Most of the work is done by the cancel tactics.
    *)
    val add_rules =
     [add_zero_left,add_zero_right,Zero_not_Suc,Suc_not_Zero,le_0_eq,
      One_nat_def,isolateSuc,
      order_less_irrefl, zero_neq_one, zero_less_one, zero_le_one,
      zero_neq_one RS not_sym, not_one_le_zero, not_one_less_zero];

    val add_mono_thms_ordered_semiring = map (fn s => prove_goal (the_context ()) s
     (fn prems => [cut_facts_tac prems 1,
                   blast_tac (claset() addIs [add_mono]) 1]))
    ["(i <= j) & (k <= l) ==> i + k <= j + (l::'a::pordered_ab_semigroup_add)",
     "(i  = j) & (k <= l) ==> i + k <= j + (l::'a::pordered_ab_semigroup_add)",
     "(i <= j) & (k  = l) ==> i + k <= j + (l::'a::pordered_ab_semigroup_add)",
     "(i  = j) & (k  = l) ==> i + k  = j + (l::'a::pordered_ab_semigroup_add)"
    ];

    val mono_ss = simpset() addsimps
                    [add_mono,add_strict_mono,add_less_le_mono,add_le_less_mono];

    val add_mono_thms_ordered_field =
      map (fn s => prove_goal (the_context ()) s
                     (fn prems => [cut_facts_tac prems 1, asm_simp_tac mono_ss 1]))
        ["(i<j) & (k=l)   ==> i+k < j+(l::'a::pordered_cancel_ab_semigroup_add)",
         "(i=j) & (k<l)   ==> i+k < j+(l::'a::pordered_cancel_ab_semigroup_add)",
         "(i<j) & (k<=l)  ==> i+k < j+(l::'a::pordered_cancel_ab_semigroup_add)",
         "(i<=j) & (k<l)  ==> i+k < j+(l::'a::pordered_cancel_ab_semigroup_add)",
         "(i<j) & (k<l)   ==> i+k < j+(l::'a::pordered_cancel_ab_semigroup_add)"];

    in

    val init_lin_arith_data =
     Fast_Arith.setup @
     [Fast_Arith.map_data (fn {add_mono_thms, mult_mono_thms, inj_thms, lessD, ...} =>
       {add_mono_thms = add_mono_thms @
        add_mono_thms_ordered_semiring @ add_mono_thms_ordered_field,
        mult_mono_thms = mult_mono_thms,
        inj_thms = inj_thms,
        lessD = lessD @ [Suc_leI],
        neqE = [linorder_neqE_nat,
          get_thm (theory "Ring_and_Field") (Name "linorder_neqE_ordered_idom")],
        simpset = HOL_basic_ss addsimps add_rules
                       addsimprocs [ab_group_add_cancel.sum_conv,
                                    ab_group_add_cancel.rel_conv]
                       (*abel_cancel helps it work in abstract algebraic domains*)
                       addsimprocs nat_cancel_sums_add}),
      ArithTheoryData.init, arith_discrete "nat"];

    end;

    val fast_nat_arith_simproc =
      Simplifier.simproc (the_context ()) "fast_nat_arith"
        ["(m::nat) < n","(m::nat) <= n", "(m::nat) = n"] Fast_Arith.lin_arith_prover;

    (* Because of fast_nat_arith_simproc, the arithmetic solver is really only
    useful to detect inconsistencies among the premises for subgoals which are
    *not* themselves (in)equalities, because the latter activate
    fast_nat_arith_simproc anyway. However, it seems cheaper to activate the
    solver all the time rather than add the additional check. *)

    (* arith proof method *)

    (* FIXME: K true should be replaced by a sensible test to speed things up
       in case there are lots of irrelevant terms involved;
       elimination of min/max can be optimized:
       (max m n + k <= r) = (m+k <= r & n+k <= r)
       (l <= min m n + k) = (l <= m+k & l <= n+k)
    *)
    local

    fun raw_arith_tac ex i st =
      refute_tac (K true)
       (REPEAT o split_tac (#splits (ArithTheoryData.get (Thm.theory_of_thm st))))
       ((REPEAT_DETERM o etac linorder_neqE) THEN' fast_ex_arith_tac ex)
       i st;

    fun presburger_tac i st =
      (case ArithTheoryData.get (Thm.theory_of_thm st) of
         {presburger = SOME tac, ...} =>
           (warning "Trying full Presburger arithmetic ..."; tac i st)
       | _ => no_tac st);

    in

    val simple_arith_tac = FIRST' [fast_arith_tac,
      ObjectLogic.atomize_tac THEN' raw_arith_tac true];

    val arith_tac = FIRST' [fast_arith_tac,
      ObjectLogic.atomize_tac THEN' raw_arith_tac true,
      presburger_tac];

    val silent_arith_tac = FIRST' [fast_arith_tac,
      ObjectLogic.atomize_tac THEN' raw_arith_tac false,
      presburger_tac];

    fun arith_method prems =
      Method.METHOD (fn facts => HEADGOAL (Method.insert_tac (prems @ facts) THEN' arith_tac));

    end;

    (* antisymmetry:
       combines x <= y (or ~(y < x)) and y <= x (or ~(x < y)) into x = y

    local
    val antisym = mk_meta_eq order_antisym
    val not_lessD = linorder_not_less RS iffD1
    fun prp t thm = (#prop(rep_thm thm) = t)
    in
    fun antisym_eq prems thm =
      let
        val r = #prop(rep_thm thm);
      in
        case r of
          Tr $ ((c as Const("op <=",T)) $ s $ t) =>
            let val r' = Tr $ (c $ t $ s)
            in
              case Library.find_first (prp r') prems of
                NONE =>
                  let val r' = Tr $ (HOLogic.Not $ (Const("op <",T) $ s $ t))
                  in case Library.find_first (prp r') prems of
                       NONE => []
                     | SOME thm' => [(thm' RS not_lessD) RS (thm RS antisym)]
                  end
              | SOME thm' => [thm' RS (thm RS antisym)]
            end
        | Tr $ (Const("Not",_) $ (Const("op <",T) $ s $ t)) =>
            let val r' = Tr $ (Const("op <=",T) $ s $ t)
            in
              case Library.find_first (prp r') prems of
                NONE =>
                  let val r' = Tr $ (HOLogic.Not $ (Const("op <",T) $ t $ s))
                  in case Library.find_first (prp r') prems of
                       NONE => []
                     | SOME thm' =>
                         [(thm' RS not_lessD) RS ((thm RS not_lessD) RS antisym)]
                  end
              | SOME thm' => [thm' RS ((thm RS not_lessD) RS antisym)]
            end
        | _ => []
      end
      handle THM _ => []
    end;
    *)

    (* theory setup *)

    val arith_setup =
     [Simplifier.change_simpset_of (op addsimprocs) nat_cancel_sums] @
      init_lin_arith_data @
      [Simplifier.change_simpset_of (op addSolver)
       (mk_solver' "lin. arith." Fast_Arith.cut_lin_arith_tac),
      Simplifier.change_simpset_of (op addsimprocs) [fast_nat_arith_simproc],
      Method.add_methods
          [("arith", (arith_method o #2) oo Method.syntax Args.bang_facts,
    	"decide linear arithmethic")],
      Attrib.add_attributes [("arith_split",
        (Attrib.no_args arith_split_add,
         Attrib.no_args Attrib.undef_local_attribute),
        "declaration of split rules for arithmetic procedure")]];