src/Provers/Arith/fast_lin_arith.ML
author haftmann
Mon May 21 19:11:42 2007 +0200 (2007-05-21)
changeset 23063 b4ee6ec4f9c6
parent 23025 7507f94adc32
child 23190 d45c4d6c5f15
permissions -rw-r--r--
tuned
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(*  Title:      Provers/Arith/fast_lin_arith.ML
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    ID:         $Id$
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    Author:     Tobias Nipkow
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    Copyright   1998  TU Munich
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A generic linear arithmetic package.
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It provides two tactics
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    lin_arith_tac:         int -> tactic
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cut_lin_arith_tac: thms -> int -> tactic
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and a simplification procedure
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    lin_arith_prover: theory -> simpset -> term -> thm option
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Only take premises and conclusions into account that are already (negated)
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(in)equations. lin_arith_prover tries to prove or disprove the term.
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*)
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(* Debugging: set Fast_Arith.trace *)
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(*** Data needed for setting up the linear arithmetic package ***)
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signature LIN_ARITH_LOGIC =
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sig
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  val conjI       : thm  (* P ==> Q ==> P & Q *)
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  val ccontr      : thm  (* (~ P ==> False) ==> P *)
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  val notI        : thm  (* (P ==> False) ==> ~ P *)
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  val not_lessD   : thm  (* ~(m < n) ==> n <= m *)
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  val not_leD     : thm  (* ~(m <= n) ==> n < m *)
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  val sym         : thm  (* x = y ==> y = x *)
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  val mk_Eq       : thm -> thm
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  val atomize     : thm -> thm list
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  val mk_Trueprop : term -> term
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  val neg_prop    : term -> term
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  val is_False    : thm -> bool
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  val is_nat      : typ list * term -> bool
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  val mk_nat_thm  : theory -> term -> thm
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end;
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(*
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mk_Eq(~in) = `in == False'
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mk_Eq(in) = `in == True'
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where `in' is an (in)equality.
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neg_prop(t) = neg  if t is wrapped up in Trueprop and
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  neg is the (logically) negated version of t, where the negation
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  of a negative term is the term itself (no double negation!);
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is_nat(parameter-types,t) =  t:nat
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mk_nat_thm(t) = "0 <= t"
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*)
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signature LIN_ARITH_DATA =
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sig
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  (* internal representation of linear (in-)equations: *)
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  type decompT = (term * Rat.rat) list * Rat.rat * string * (term * Rat.rat) list * Rat.rat * bool
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  val decomp: theory -> term -> decompT option
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  val domain_is_nat : term -> bool
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  (* preprocessing, performed on a representation of subgoals as list of premises: *)
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  val pre_decomp: theory -> typ list * term list -> (typ list * term list) list
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  (* preprocessing, performed on the goal -- must do the same as 'pre_decomp': *)
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  val pre_tac   : int -> Tactical.tactic
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  val number_of : IntInf.int * typ -> term
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end;
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(*
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decomp(`x Rel y') should yield (p,i,Rel,q,j,d)
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   where Rel is one of "<", "~<", "<=", "~<=" and "=" and
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         p (q, respectively) is the decomposition of the sum term x
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         (y, respectively) into a list of summand * multiplicity
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         pairs and a constant summand and d indicates if the domain
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         is discrete.
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domain_is_nat(`x Rel y') t should yield true iff x is of type "nat".
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The relationship between pre_decomp and pre_tac is somewhat tricky.  The
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internal representation of a subgoal and the corresponding theorem must
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be modified by pre_decomp (pre_tac, resp.) in a corresponding way.  See
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the comment for split_items below.  (This is even necessary for eta- and
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beta-equivalent modifications, as some of the lin. arith. code is not
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insensitive to them.)
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ss must reduce contradictory <= to False.
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   It should also cancel common summands to keep <= reduced;
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   otherwise <= can grow to massive proportions.
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*)
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signature FAST_LIN_ARITH =
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sig
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  val map_data: ({add_mono_thms: thm list, mult_mono_thms: thm list, inj_thms: thm list,
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                 lessD: thm list, neqE: thm list, simpset: Simplifier.simpset}
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                 -> {add_mono_thms: thm list, mult_mono_thms: thm list, inj_thms: thm list,
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                     lessD: thm list, neqE: thm list, simpset: Simplifier.simpset})
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                -> theory -> theory
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  val trace: bool ref
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  val fast_arith_neq_limit: int ref
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  val lin_arith_prover: theory -> simpset -> term -> thm option
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  val     lin_arith_tac:    bool -> int -> tactic
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  val cut_lin_arith_tac: simpset -> int -> tactic
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end;
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functor Fast_Lin_Arith(structure LA_Logic:LIN_ARITH_LOGIC
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                       and       LA_Data:LIN_ARITH_DATA) : FAST_LIN_ARITH =
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struct
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(** theory data **)
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structure Data = TheoryDataFun
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(
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  type T = {add_mono_thms: thm list, mult_mono_thms: thm list, inj_thms: thm list,
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            lessD: thm list, neqE: thm list, simpset: Simplifier.simpset};
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  val empty = {add_mono_thms = [], mult_mono_thms = [], inj_thms = [],
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               lessD = [], neqE = [], simpset = Simplifier.empty_ss};
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  val copy = I;
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  val extend = I;
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  fun merge _
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    ({add_mono_thms= add_mono_thms1, mult_mono_thms= mult_mono_thms1, inj_thms= inj_thms1,
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      lessD = lessD1, neqE=neqE1, simpset = simpset1},
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     {add_mono_thms= add_mono_thms2, mult_mono_thms= mult_mono_thms2, inj_thms= inj_thms2,
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      lessD = lessD2, neqE=neqE2, simpset = simpset2}) =
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    {add_mono_thms = Drule.merge_rules (add_mono_thms1, add_mono_thms2),
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     mult_mono_thms = Drule.merge_rules (mult_mono_thms1, mult_mono_thms2),
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     inj_thms = Drule.merge_rules (inj_thms1, inj_thms2),
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     lessD = Drule.merge_rules (lessD1, lessD2),
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     neqE = Drule.merge_rules (neqE1, neqE2),
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     simpset = Simplifier.merge_ss (simpset1, simpset2)};
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);
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val map_data = Data.map;
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(*** A fast decision procedure ***)
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(*** Code ported from HOL Light ***)
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(* possible optimizations:
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   use (var,coeff) rep or vector rep  tp save space;
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   treat non-negative atoms separately rather than adding 0 <= atom
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*)
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val trace = ref false;
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datatype lineq_type = Eq | Le | Lt;
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datatype injust = Asm of int
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                | Nat of int (* index of atom *)
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                | LessD of injust
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                | NotLessD of injust
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                | NotLeD of injust
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                | NotLeDD of injust
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                | Multiplied of IntInf.int * injust
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                | Multiplied2 of IntInf.int * injust
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                | Added of injust * injust;
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datatype lineq = Lineq of IntInf.int * lineq_type * IntInf.int list * injust;
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(* ------------------------------------------------------------------------- *)
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(* Finding a (counter) example from the trace of a failed elimination        *)
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(* ------------------------------------------------------------------------- *)
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(* Examples are represented as rational numbers,                             *)
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(* Dont blame John Harrison for this code - it is entirely mine. TN          *)
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exception NoEx;
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(* Coding: (i,true,cs) means i <= cs and (i,false,cs) means i < cs.
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   In general, true means the bound is included, false means it is excluded.
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   Need to know if it is a lower or upper bound for unambiguous interpretation!
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*)
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fun elim_eqns (Lineq (i, Le, cs, _)) = [(i, true, cs)]
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  | elim_eqns (Lineq (i, Eq, cs, _)) = [(i, true, cs),(~i, true, map ~ cs)]
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  | elim_eqns (Lineq (i, Lt, cs, _)) = [(i, false, cs)];
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(* PRE: ex[v] must be 0! *)
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fun eval ex v (a:IntInf.int,le,cs:IntInf.int list) =
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  let
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    val rs = map Rat.rat_of_int cs;
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    val rsum = fold2 (Rat.add oo Rat.mult) rs ex Rat.zero;
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  in (Rat.mult (Rat.add (Rat.rat_of_int a) (Rat.neg rsum)) (Rat.inv (nth rs v)), le) end;
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(* If nth rs v < 0, le should be negated.
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   Instead this swap is taken into account in ratrelmin2.
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*)
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fun ratrelmin2 (x as (r, ler), y as (s, les)) =
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  case Rat.cmp (r, s)
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   of EQUAL => (r, (not ler) andalso (not les))
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    | LESS => x
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    | GREATER => y;
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fun ratrelmax2 (x as (r, ler), y as (s, les)) =
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  case Rat.cmp (r, s)
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   of EQUAL => (r, ler andalso les)
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    | LESS => y
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    | GREATER => x;
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val ratrelmin = foldr1 ratrelmin2;
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val ratrelmax = foldr1 ratrelmax2;
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fun ratexact up (r, exact) =
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  if exact then r else
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  let
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    val (p, q) = Rat.quotient_of_rat r;
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    val nth = Rat.inv (Rat.rat_of_int q);
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  in Rat.add r (if up then nth else Rat.neg nth) end;
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fun ratmiddle (r, s) = Rat.mult (Rat.add r s) (Rat.inv Rat.two);
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fun choose2 d ((lb, exactl), (ub, exactu)) =
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  let val ord = Rat.cmp_zero lb in
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  if (ord = LESS orelse exactl) andalso (ord = GREATER orelse exactu)
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    then Rat.zero
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    else if not d then
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      if ord = GREATER
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        then if exactl then lb else ratmiddle (lb, ub)
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        else if exactu then ub else ratmiddle (lb, ub)
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      else (*discrete domain, both bounds must be exact*)
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      if ord = GREATER
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        then let val lb' = Rat.roundup lb in
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          if Rat.le lb' ub then lb' else raise NoEx end
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        else let val ub' = Rat.rounddown ub in
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          if Rat.le lb ub' then ub' else raise NoEx end
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  end;
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fun findex1 discr (v, lineqs) ex =
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  let
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    val nz = filter (fn (Lineq (_, _, cs, _)) => nth cs v <> 0) lineqs;
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    val ineqs = maps elim_eqns nz;
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    val (ge, le) = List.partition (fn (_,_,cs) => nth cs v > 0) ineqs
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    val lb = ratrelmax (map (eval ex v) ge)
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    val ub = ratrelmin (map (eval ex v) le)
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  in nth_map v (K (choose2 (nth discr v) (lb, ub))) ex end;
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fun elim1 v x =
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  map (fn (a,le,bs) => (Rat.add a (Rat.neg (Rat.mult (nth bs v) x)), le,
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                        nth_map v (K Rat.zero) bs));
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fun single_var v (_, _, cs) = case filter_out (curry (op =) EQUAL o Rat.cmp_zero) cs
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 of [x] => x =/ nth cs v
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  | _ => false;
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(* The base case:
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   all variables occur only with positive or only with negative coefficients *)
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fun pick_vars discr (ineqs,ex) =
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  let val nz = filter_out (fn (_,_,cs) => forall (curry (op =) EQUAL o Rat.cmp_zero) cs) ineqs
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  in case nz of [] => ex
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     | (_,_,cs) :: _ =>
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       let val v = find_index (not o curry (op =) EQUAL o Rat.cmp_zero) cs
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           val d = nth discr v;
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           val pos = not (Rat.cmp_zero (nth cs v) = LESS);
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           val sv = filter (single_var v) nz;
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           val minmax =
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             if pos then if d then Rat.roundup o fst o ratrelmax
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                         else ratexact true o ratrelmax
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                    else if d then Rat.rounddown o fst o ratrelmin
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                         else ratexact false o ratrelmin
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           val bnds = map (fn (a,le,bs) => (Rat.mult a (Rat.inv (nth bs v)), le)) sv
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           val x = minmax((Rat.zero,if pos then true else false)::bnds)
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           val ineqs' = elim1 v x nz
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           val ex' = nth_map v (K x) ex
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       in pick_vars discr (ineqs',ex') end
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  end;
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fun findex0 discr n lineqs =
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  let val ineqs = maps elim_eqns lineqs
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      val rineqs = map (fn (a,le,cs) => (Rat.rat_of_int a, le, map Rat.rat_of_int cs))
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                       ineqs
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  in pick_vars discr (rineqs,replicate n Rat.zero) end;
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(* ------------------------------------------------------------------------- *)
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(* End of counter example finder. The actual decision procedure starts here. *)
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(* ------------------------------------------------------------------------- *)
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(* ------------------------------------------------------------------------- *)
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(* Calculate new (in)equality type after addition.                           *)
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(* ------------------------------------------------------------------------- *)
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fun find_add_type(Eq,x) = x
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  | find_add_type(x,Eq) = x
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  | find_add_type(_,Lt) = Lt
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  | find_add_type(Lt,_) = Lt
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  | find_add_type(Le,Le) = Le;
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(* ------------------------------------------------------------------------- *)
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(* Multiply out an (in)equation.                                             *)
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(* ------------------------------------------------------------------------- *)
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fun multiply_ineq n (i as Lineq(k,ty,l,just)) =
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  if n = 1 then i
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  else if n = 0 andalso ty = Lt then sys_error "multiply_ineq"
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  else if n < 0 andalso (ty=Le orelse ty=Lt) then sys_error "multiply_ineq"
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  else Lineq (n * k, ty, map (curry op* n) l, Multiplied (n, just));
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(* ------------------------------------------------------------------------- *)
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(* Add together (in)equations.                                               *)
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(* ------------------------------------------------------------------------- *)
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fun add_ineq (i1 as Lineq(k1,ty1,l1,just1)) (i2 as Lineq(k2,ty2,l2,just2)) =
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  let val l = map2 (curry (op +)) l1 l2
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  in Lineq(k1+k2,find_add_type(ty1,ty2),l,Added(just1,just2)) end;
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(* ------------------------------------------------------------------------- *)
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(* Elimination of variable between a single pair of (in)equations.           *)
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(* If they're both inequalities, 1st coefficient must be +ve, 2nd -ve.       *)
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(* ------------------------------------------------------------------------- *)
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fun elim_var v (i1 as Lineq(k1,ty1,l1,just1)) (i2 as Lineq(k2,ty2,l2,just2)) =
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  let val c1 = nth l1 v and c2 = nth l2 v
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      val m = lcm(abs c1, abs c2)
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      val m1 = m div (abs c1) and m2 = m div (abs c2)
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      val (n1,n2) =
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        if (c1 >= 0) = (c2 >= 0)
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        then if ty1 = Eq then (~m1,m2)
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             else if ty2 = Eq then (m1,~m2)
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                  else sys_error "elim_var"
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        else (m1,m2)
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      val (p1,p2) = if ty1=Eq andalso ty2=Eq andalso (n1 = ~1 orelse n2 = ~1)
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                    then (~n1,~n2) else (n1,n2)
nipkow@5982
   319
  in add_ineq (multiply_ineq n1 i1) (multiply_ineq n2 i2) end;
nipkow@5982
   320
nipkow@5982
   321
(* ------------------------------------------------------------------------- *)
nipkow@5982
   322
(* The main refutation-finding code.                                         *)
nipkow@5982
   323
(* ------------------------------------------------------------------------- *)
nipkow@5982
   324
nipkow@5982
   325
fun is_trivial (Lineq(_,_,l,_)) = forall (fn i => i=0) l;
nipkow@5982
   326
nipkow@5982
   327
fun is_answer (ans as Lineq(k,ty,l,_)) =
nipkow@5982
   328
  case ty  of Eq => k <> 0 | Le => k > 0 | Lt => k >= 0;
nipkow@5982
   329
nipkow@16358
   330
fun calc_blowup (l:IntInf.int list) =
haftmann@17496
   331
  let val (p,n) = List.partition (curry (op <) 0) (List.filter (curry (op <>) 0) l)
nipkow@5982
   332
  in (length p) * (length n) end;
nipkow@5982
   333
nipkow@5982
   334
(* ------------------------------------------------------------------------- *)
nipkow@5982
   335
(* Main elimination code:                                                    *)
nipkow@5982
   336
(*                                                                           *)
nipkow@5982
   337
(* (1) Looks for immediate solutions (false assertions with no variables).   *)
nipkow@5982
   338
(*                                                                           *)
nipkow@5982
   339
(* (2) If there are any equations, picks a variable with the lowest absolute *)
nipkow@5982
   340
(* coefficient in any of them, and uses it to eliminate.                     *)
nipkow@5982
   341
(*                                                                           *)
nipkow@5982
   342
(* (3) Otherwise, chooses a variable in the inequality to minimize the       *)
nipkow@5982
   343
(* blowup (number of consequences generated) and eliminates it.              *)
nipkow@5982
   344
(* ------------------------------------------------------------------------- *)
nipkow@5982
   345
nipkow@5982
   346
fun allpairs f xs ys =
webertj@20217
   347
  List.concat (map (fn x => map (fn y => f x y) ys) xs);
nipkow@5982
   348
nipkow@5982
   349
fun extract_first p =
skalberg@15531
   350
  let fun extract xs (y::ys) = if p y then (SOME y,xs@ys)
nipkow@5982
   351
                               else extract (y::xs) ys
skalberg@15531
   352
        | extract xs []      = (NONE,xs)
nipkow@5982
   353
  in extract [] end;
nipkow@5982
   354
nipkow@6056
   355
fun print_ineqs ineqs =
paulson@9073
   356
  if !trace then
wenzelm@12262
   357
     tracing(cat_lines(""::map (fn Lineq(c,t,l,_) =>
nipkow@16358
   358
       IntInf.toString c ^
paulson@9073
   359
       (case t of Eq => " =  " | Lt=> " <  " | Le => " <= ") ^
nipkow@16358
   360
       commas(map IntInf.toString l)) ineqs))
paulson@9073
   361
  else ();
nipkow@6056
   362
nipkow@13498
   363
type history = (int * lineq list) list;
nipkow@13498
   364
datatype result = Success of injust | Failure of history;
nipkow@13498
   365
webertj@20217
   366
fun elim (ineqs, hist) =
webertj@20217
   367
  let val dummy = print_ineqs ineqs
webertj@20217
   368
      val (triv, nontriv) = List.partition is_trivial ineqs in
webertj@20217
   369
  if not (null triv)
nipkow@13186
   370
  then case Library.find_first is_answer triv of
webertj@20217
   371
         NONE => elim (nontriv, hist)
skalberg@15531
   372
       | SOME(Lineq(_,_,_,j)) => Success j
nipkow@5982
   373
  else
webertj@20217
   374
  if null nontriv then Failure hist
nipkow@13498
   375
  else
webertj@20217
   376
  let val (eqs, noneqs) = List.partition (fn (Lineq(_,ty,_,_)) => ty=Eq) nontriv in
webertj@20217
   377
  if not (null eqs) then
skalberg@15570
   378
     let val clist = Library.foldl (fn (cs,Lineq(_,_,l,_)) => l union cs) ([],eqs)
nipkow@16358
   379
         val sclist = sort (fn (x,y) => IntInf.compare(abs(x),abs(y)))
skalberg@15570
   380
                           (List.filter (fn i => i<>0) clist)
nipkow@5982
   381
         val c = hd sclist
skalberg@15531
   382
         val (SOME(eq as Lineq(_,_,ceq,_)),othereqs) =
nipkow@5982
   383
               extract_first (fn Lineq(_,_,l,_) => c mem l) eqs
webertj@20217
   384
         val v = find_index_eq c ceq
haftmann@23063
   385
         val (ioth,roth) = List.partition (fn (Lineq(_,_,l,_)) => nth l v = 0)
nipkow@5982
   386
                                     (othereqs @ noneqs)
nipkow@5982
   387
         val others = map (elim_var v eq) roth @ ioth
nipkow@13498
   388
     in elim(others,(v,nontriv)::hist) end
nipkow@5982
   389
  else
nipkow@5982
   390
  let val lists = map (fn (Lineq(_,_,l,_)) => l) noneqs
haftmann@23063
   391
      val numlist = 0 upto (length (hd lists) - 1)
haftmann@23063
   392
      val coeffs = map (fn i => map (fn xs => nth xs i) lists) numlist
nipkow@5982
   393
      val blows = map calc_blowup coeffs
nipkow@5982
   394
      val iblows = blows ~~ numlist
haftmann@23063
   395
      val nziblows = filter_out (fn (i, _) => i = 0) iblows
nipkow@13498
   396
  in if null nziblows then Failure((~1,nontriv)::hist)
nipkow@13498
   397
     else
nipkow@5982
   398
     let val (c,v) = hd(sort (fn (x,y) => int_ord(fst(x),fst(y))) nziblows)
haftmann@23063
   399
         val (no,yes) = List.partition (fn (Lineq(_,_,l,_)) => nth l v = 0) ineqs
haftmann@23063
   400
         val (pos,neg) = List.partition(fn (Lineq(_,_,l,_)) => nth l v > 0) yes
nipkow@13498
   401
     in elim(no @ allpairs (elim_var v) pos neg, (v,nontriv)::hist) end
nipkow@5982
   402
  end
nipkow@5982
   403
  end
nipkow@5982
   404
  end;
nipkow@5982
   405
nipkow@5982
   406
(* ------------------------------------------------------------------------- *)
nipkow@5982
   407
(* Translate back a proof.                                                   *)
nipkow@5982
   408
(* ------------------------------------------------------------------------- *)
nipkow@5982
   409
webertj@20268
   410
fun trace_thm (msg : string) (th : thm) : thm =
webertj@20217
   411
    (if !trace then (tracing msg; tracing (Display.string_of_thm th)) else (); th);
paulson@9073
   412
webertj@20268
   413
fun trace_msg (msg : string) : unit =
wenzelm@12262
   414
    if !trace then tracing msg else ();
paulson@9073
   415
nipkow@13498
   416
(* FIXME OPTIMIZE!!!! (partly done already)
nipkow@6056
   417
   Addition/Multiplication need i*t representation rather than t+t+...
nipkow@10691
   418
   Get rid of Mulitplied(2). For Nat LA_Data.number_of should return Suc^n
nipkow@10691
   419
   because Numerals are not known early enough.
nipkow@6056
   420
nipkow@6056
   421
Simplification may detect a contradiction 'prematurely' due to type
nipkow@6056
   422
information: n+1 <= 0 is simplified to False and does not need to be crossed
nipkow@6056
   423
with 0 <= n.
nipkow@6056
   424
*)
nipkow@6056
   425
local
nipkow@6056
   426
 exception FalseE of thm
nipkow@6056
   427
in
wenzelm@22846
   428
fun mkthm (sg:theory, ss) (asms:thm list) (just:injust) : thm =
nipkow@15922
   429
  let val {add_mono_thms, mult_mono_thms, inj_thms, lessD, simpset, ...} =
wenzelm@16458
   430
          Data.get sg;
wenzelm@17877
   431
      val simpset' = Simplifier.inherit_context ss simpset;
webertj@20217
   432
      val atoms = Library.foldl (fn (ats, (lhs,_,_,rhs,_,_)) =>
nipkow@6056
   433
                            map fst lhs  union  (map fst rhs  union  ats))
webertj@20217
   434
                        ([], List.mapPartial (fn thm => if Thm.no_prems thm
webertj@20217
   435
                                              then LA_Data.decomp sg (concl_of thm)
webertj@20217
   436
                                              else NONE) asms)
nipkow@6056
   437
nipkow@10575
   438
      fun add2 thm1 thm2 =
nipkow@6102
   439
        let val conj = thm1 RS (thm2 RS LA_Logic.conjI)
skalberg@15531
   440
        in get_first (fn th => SOME(conj RS th) handle THM _ => NONE) add_mono_thms
nipkow@5982
   441
        end;
skalberg@15531
   442
      fun try_add [] _ = NONE
nipkow@10575
   443
        | try_add (thm1::thm1s) thm2 = case add2 thm1 thm2 of
skalberg@15531
   444
             NONE => try_add thm1s thm2 | some => some;
nipkow@10575
   445
nipkow@10575
   446
      fun addthms thm1 thm2 =
nipkow@10575
   447
        case add2 thm1 thm2 of
skalberg@15531
   448
          NONE => (case try_add ([thm1] RL inj_thms) thm2 of
webertj@20217
   449
                     NONE => ( the (try_add ([thm2] RL inj_thms) thm1)
wenzelm@15660
   450
                               handle Option =>
nipkow@14360
   451
                               (trace_thm "" thm1; trace_thm "" thm2;
webertj@20217
   452
                                sys_error "Lin.arith. failed to add thms")
webertj@20217
   453
                             )
skalberg@15531
   454
                   | SOME thm => thm)
skalberg@15531
   455
        | SOME thm => thm;
nipkow@10575
   456
nipkow@5982
   457
      fun multn(n,thm) =
nipkow@5982
   458
        let fun mul(i,th) = if i=1 then th else mul(i-1, addthms thm th)
nipkow@6102
   459
        in if n < 0 then mul(~n,thm) RS LA_Logic.sym else mul(n,thm) end;
webertj@20217
   460
nipkow@15184
   461
      fun multn2(n,thm) =
skalberg@15531
   462
        let val SOME(mth) =
skalberg@15531
   463
              get_first (fn th => SOME(thm RS th) handle THM _ => NONE) mult_mono_thms
wenzelm@22596
   464
            fun cvar(th,_ $ (_ $ _ $ var)) = cterm_of (Thm.theory_of_thm th) var;
nipkow@15184
   465
            val cv = cvar(mth, hd(prems_of mth));
nipkow@15184
   466
            val ct = cterm_of sg (LA_Data.number_of(n,#T(rep_cterm cv)))
nipkow@15184
   467
        in instantiate ([],[(cv,ct)]) mth end
nipkow@10691
   468
nipkow@6056
   469
      fun simp thm =
wenzelm@17515
   470
        let val thm' = trace_thm "Simplified:" (full_simplify simpset' thm)
nipkow@6102
   471
        in if LA_Logic.is_False thm' then raise FalseE thm' else thm' end
nipkow@6056
   472
webertj@20276
   473
      fun mk (Asm i)              = trace_thm ("Asm " ^ Int.toString i) (nth asms i)
webertj@20276
   474
        | mk (Nat i)              = trace_thm ("Nat " ^ Int.toString i) (LA_Logic.mk_nat_thm sg (nth atoms i))
webertj@20254
   475
        | mk (LessD j)            = trace_thm "L" (hd ([mk j] RL lessD))
webertj@20254
   476
        | mk (NotLeD j)           = trace_thm "NLe" (mk j RS LA_Logic.not_leD)
webertj@20254
   477
        | mk (NotLeDD j)          = trace_thm "NLeD" (hd ([mk j RS LA_Logic.not_leD] RL lessD))
webertj@20254
   478
        | mk (NotLessD j)         = trace_thm "NL" (mk j RS LA_Logic.not_lessD)
webertj@20254
   479
        | mk (Added (j1, j2))     = simp (trace_thm "+" (addthms (mk j1) (mk j2)))
webertj@20254
   480
        | mk (Multiplied (n, j))  = (trace_msg ("*" ^ IntInf.toString n); trace_thm "*" (multn (n, mk j)))
webertj@20254
   481
        | mk (Multiplied2 (n, j)) = simp (trace_msg ("**" ^ IntInf.toString n); trace_thm "**" (multn2 (n, mk j)))
nipkow@5982
   482
paulson@9073
   483
  in trace_msg "mkthm";
nipkow@12932
   484
     let val thm = trace_thm "Final thm:" (mk just)
wenzelm@17515
   485
     in let val fls = simplify simpset' thm
nipkow@13186
   486
        in trace_thm "After simplification:" fls;
nipkow@13186
   487
           if LA_Logic.is_False fls then fls
nipkow@13186
   488
           else
webertj@20217
   489
            (tracing "Assumptions:"; List.app (tracing o Display.string_of_thm) asms;
webertj@20217
   490
             tracing "Proved:"; tracing (Display.string_of_thm fls);
nipkow@13186
   491
             warning "Linear arithmetic should have refuted the assumptions.\n\
nipkow@13186
   492
                     \Please inform Tobias Nipkow (nipkow@in.tum.de).";
nipkow@13186
   493
             fls)
nipkow@12932
   494
        end
webertj@20217
   495
     end handle FalseE thm => trace_thm "False reached early:" thm
nipkow@12932
   496
  end
nipkow@6056
   497
end;
nipkow@5982
   498
nipkow@16358
   499
fun coeff poly atom : IntInf.int =
haftmann@17325
   500
  AList.lookup (op =) poly atom |> the_default 0;
nipkow@5982
   501
webertj@20280
   502
fun lcms (is : IntInf.int list) : IntInf.int = Library.foldl lcm (1, is);
nipkow@10691
   503
nipkow@10691
   504
fun integ(rlhs,r,rel,rrhs,s,d) =
haftmann@17951
   505
let val (rn,rd) = Rat.quotient_of_rat r and (sn,sd) = Rat.quotient_of_rat s
haftmann@17951
   506
    val m = lcms(map (abs o snd o Rat.quotient_of_rat) (r :: s :: map snd rlhs @ map snd rrhs))
wenzelm@22846
   507
    fun mult(t,r) =
haftmann@17951
   508
        let val (i,j) = Rat.quotient_of_rat r
paulson@15965
   509
        in (t,i * (m div j)) end
nipkow@12932
   510
in (m,(map mult rlhs, rn*(m div rd), rel, map mult rrhs, sn*(m div sd), d)) end
nipkow@10691
   511
nipkow@13498
   512
fun mklineq n atoms =
webertj@20217
   513
  fn (item, k) =>
webertj@20217
   514
  let val (m, (lhs,i,rel,rhs,j,discrete)) = integ item
nipkow@13498
   515
      val lhsa = map (coeff lhs) atoms
nipkow@13498
   516
      and rhsa = map (coeff rhs) atoms
haftmann@18330
   517
      val diff = map2 (curry (op -)) rhsa lhsa
nipkow@13498
   518
      val c = i-j
nipkow@13498
   519
      val just = Asm k
nipkow@13498
   520
      fun lineq(c,le,cs,j) = Lineq(c,le,cs, if m=1 then j else Multiplied2(m,j))
nipkow@13498
   521
  in case rel of
nipkow@13498
   522
      "<="   => lineq(c,Le,diff,just)
nipkow@13498
   523
     | "~<=" => if discrete
nipkow@13498
   524
                then lineq(1-c,Le,map (op ~) diff,NotLeDD(just))
nipkow@13498
   525
                else lineq(~c,Lt,map (op ~) diff,NotLeD(just))
nipkow@13498
   526
     | "<"   => if discrete
nipkow@13498
   527
                then lineq(c+1,Le,diff,LessD(just))
nipkow@13498
   528
                else lineq(c,Lt,diff,just)
nipkow@13498
   529
     | "~<"  => lineq(~c,Le,map (op~) diff,NotLessD(just))
nipkow@13498
   530
     | "="   => lineq(c,Eq,diff,just)
wenzelm@22846
   531
     | _     => sys_error("mklineq" ^ rel)
nipkow@5982
   532
  end;
nipkow@5982
   533
nipkow@13498
   534
(* ------------------------------------------------------------------------- *)
nipkow@13498
   535
(* Print (counter) example                                                   *)
nipkow@13498
   536
(* ------------------------------------------------------------------------- *)
nipkow@13498
   537
nipkow@13498
   538
fun print_atom((a,d),r) =
haftmann@17951
   539
  let val (p,q) = Rat.quotient_of_rat r
paulson@15965
   540
      val s = if d then IntInf.toString p else
nipkow@13498
   541
              if p = 0 then "0"
paulson@15965
   542
              else IntInf.toString p ^ "/" ^ IntInf.toString q
nipkow@13498
   543
  in a ^ " = " ^ s end;
nipkow@13498
   544
wenzelm@19049
   545
fun produce_ex sds =
haftmann@17496
   546
  curry (op ~~) sds
haftmann@17496
   547
  #> map print_atom
haftmann@17496
   548
  #> commas
webertj@20217
   549
  #> curry (op ^) "Counter example (possibly spurious):\n";
nipkow@13498
   550
webertj@20217
   551
fun trace_ex (sg, params, atoms, discr, n, hist : history) =
webertj@20217
   552
  case hist of
webertj@20217
   553
    [] => ()
webertj@20217
   554
  | (v, lineqs) :: hist' =>
webertj@20217
   555
    let val frees = map Free params
webertj@20217
   556
        fun s_of_t t = Sign.string_of_term sg (subst_bounds (frees, t))
haftmann@22950
   557
        val start = if v = ~1 then (hist', findex0 discr n lineqs)
haftmann@22950
   558
          else (hist, replicate n Rat.zero)
haftmann@22950
   559
        val ex = SOME (produce_ex ((map s_of_t atoms) ~~ discr)
haftmann@22950
   560
          (uncurry (fold (findex1 discr)) start))
webertj@20217
   561
          handle NoEx => NONE
webertj@20217
   562
    in
webertj@20217
   563
      case ex of
webertj@20217
   564
        SOME s => (warning "arith failed - see trace for a counter example"; tracing s)
webertj@20217
   565
      | NONE => warning "arith failed"
webertj@20217
   566
    end;
nipkow@13498
   567
webertj@20217
   568
(* ------------------------------------------------------------------------- *)
webertj@20217
   569
webertj@20268
   570
fun mknat (pTs : typ list) (ixs : int list) (atom : term, i : int) : lineq option =
webertj@20217
   571
  if LA_Logic.is_nat (pTs, atom)
nipkow@6056
   572
  then let val l = map (fn j => if j=i then 1 else 0) ixs
webertj@20217
   573
       in SOME (Lineq (0, Le, l, Nat i)) end
webertj@20217
   574
  else NONE;
nipkow@6056
   575
nipkow@13186
   576
(* This code is tricky. It takes a list of premises in the order they occur
skalberg@15531
   577
in the subgoal. Numerical premises are coded as SOME(tuple), non-numerical
skalberg@15531
   578
ones as NONE. Going through the premises, each numeric one is converted into
nipkow@13186
   579
a Lineq. The tricky bit is to convert ~= which is split into two cases < and
nipkow@13498
   580
>. Thus split_items returns a list of equation systems. This may blow up if
nipkow@13186
   581
there are many ~=, but in practice it does not seem to happen. The really
nipkow@13186
   582
tricky bit is to arrange the order of the cases such that they coincide with
nipkow@13186
   583
the order in which the cases are in the end generated by the tactic that
nipkow@13186
   584
applies the generated refutation thms (see function 'refute_tac').
nipkow@13186
   585
nipkow@13186
   586
For variables n of type nat, a constraint 0 <= n is added.
nipkow@13186
   587
*)
webertj@20217
   588
webertj@20217
   589
(* FIXME: To optimize, the splitting of cases and the search for refutations *)
webertj@20276
   590
(*        could be intertwined: separate the first (fully split) case,       *)
webertj@20217
   591
(*        refute it, continue with splitting and refuting.  Terminate with   *)
webertj@20217
   592
(*        failure as soon as a case could not be refuted; i.e. delay further *)
webertj@20217
   593
(*        splitting until after a refutation for other cases has been found. *)
webertj@20217
   594
wenzelm@22846
   595
fun split_items sg (do_pre : bool) (Ts, terms) :
webertj@20276
   596
                (typ list * (LA_Data.decompT * int) list) list =
webertj@20276
   597
let
webertj@20276
   598
  (* splits inequalities '~=' into '<' and '>'; this corresponds to *)
webertj@20276
   599
  (* 'REPEAT_DETERM (eresolve_tac neqE i)' at the theorem/tactic    *)
webertj@20276
   600
  (* level                                                          *)
webertj@20276
   601
  (* FIXME: this is currently sensitive to the order of theorems in *)
webertj@20276
   602
  (*        neqE:  The theorem for type "nat" must come first.  A   *)
webertj@20276
   603
  (*        better (i.e. less likely to break when neqE changes)    *)
webertj@20276
   604
  (*        implementation should *test* which theorem from neqE    *)
webertj@20276
   605
  (*        can be applied, and split the premise accordingly.      *)
webertj@20276
   606
  fun elim_neq (ineqs : (LA_Data.decompT option * bool) list) :
webertj@20276
   607
               (LA_Data.decompT option * bool) list list =
webertj@20276
   608
  let
webertj@20276
   609
    fun elim_neq' nat_only ([] : (LA_Data.decompT option * bool) list) :
webertj@20276
   610
                  (LA_Data.decompT option * bool) list list =
webertj@20276
   611
          [[]]
webertj@20276
   612
      | elim_neq' nat_only ((NONE, is_nat) :: ineqs) =
webertj@20276
   613
          map (cons (NONE, is_nat)) (elim_neq' nat_only ineqs)
webertj@20276
   614
      | elim_neq' nat_only ((ineq as (SOME (l, i, rel, r, j, d), is_nat)) :: ineqs) =
webertj@20276
   615
          if rel = "~=" andalso (not nat_only orelse is_nat) then
webertj@20276
   616
            (* [| ?l ~= ?r; ?l < ?r ==> ?R; ?r < ?l ==> ?R |] ==> ?R *)
webertj@20276
   617
            elim_neq' nat_only (ineqs @ [(SOME (l, i, "<", r, j, d), is_nat)]) @
webertj@20276
   618
            elim_neq' nat_only (ineqs @ [(SOME (r, j, "<", l, i, d), is_nat)])
webertj@20276
   619
          else
webertj@20276
   620
            map (cons ineq) (elim_neq' nat_only ineqs)
webertj@20276
   621
  in
webertj@20276
   622
    ineqs |> elim_neq' true
webertj@20276
   623
          |> map (elim_neq' false)
webertj@20276
   624
          |> List.concat
webertj@20276
   625
  end
nipkow@13464
   626
webertj@20276
   627
  fun number_hyps _ []             = []
webertj@20276
   628
    | number_hyps n (NONE::xs)     = number_hyps (n+1) xs
webertj@20276
   629
    | number_hyps n ((SOME x)::xs) = (x, n) :: number_hyps (n+1) xs
webertj@20276
   630
webertj@20276
   631
  val result = (Ts, terms)
webertj@20276
   632
    |> (* user-defined preprocessing of the subgoal *)
webertj@20433
   633
       (if do_pre then LA_Data.pre_decomp sg else Library.single)
wenzelm@22846
   634
    |> (* produce the internal encoding of (in-)equalities *)
webertj@20276
   635
       map (apsnd (map (fn t => (LA_Data.decomp sg t, LA_Data.domain_is_nat t))))
webertj@20276
   636
    |> (* splitting of inequalities *)
webertj@20276
   637
       map (apsnd elim_neq)
wenzelm@22846
   638
    |> maps (fn (Ts, subgoals) => map (pair Ts o map fst) subgoals)
webertj@20276
   639
    |> (* numbering of hypotheses, ignoring irrelevant ones *)
webertj@20276
   640
       map (apsnd (number_hyps 0))
webertj@20276
   641
in result end;
nipkow@13464
   642
webertj@20268
   643
fun add_atoms (ats : term list, ((lhs,_,_,rhs,_,_) : LA_Data.decompT, _)) : term list =
webertj@20217
   644
    (map fst lhs) union ((map fst rhs) union ats);
webertj@20217
   645
webertj@20268
   646
fun add_datoms (dats : (bool * term) list, ((lhs,_,_,rhs,_,d) : LA_Data.decompT, _)) :
webertj@20268
   647
  (bool * term) list =
webertj@20268
   648
  (map (pair d o fst) lhs) union ((map (pair d o fst) rhs) union dats);
nipkow@13498
   649
webertj@20268
   650
fun discr (initems : (LA_Data.decompT * int) list) : bool list =
webertj@20268
   651
  map fst (Library.foldl add_datoms ([],initems));
webertj@20217
   652
webertj@20268
   653
fun refutes (sg : theory) (params : (string * typ) list) (show_ex : bool) :
webertj@20268
   654
  (typ list * (LA_Data.decompT * int) list) list -> injust list -> injust list option =
nipkow@13498
   655
let
webertj@20268
   656
  fun refute ((Ts : typ list, initems : (LA_Data.decompT * int) list)::initemss)
webertj@20268
   657
             (js : injust list) : injust list option =
webertj@20217
   658
    let val atoms = Library.foldl add_atoms ([], initems)
nipkow@13498
   659
        val n = length atoms
nipkow@13498
   660
        val mkleq = mklineq n atoms
nipkow@13498
   661
        val ixs = 0 upto (n-1)
nipkow@13498
   662
        val iatoms = atoms ~~ ixs
webertj@20217
   663
        val natlineqs = List.mapPartial (mknat Ts ixs) iatoms
nipkow@13498
   664
        val ineqs = map mkleq initems @ natlineqs
webertj@20217
   665
    in case elim (ineqs, []) of
webertj@20217
   666
         Success j =>
webertj@20268
   667
           (trace_msg ("Contradiction! (" ^ Int.toString (length js + 1) ^ ")");
webertj@20268
   668
            refute initemss (js@[j]))
webertj@20217
   669
       | Failure hist =>
webertj@20217
   670
           (if not show_ex then
webertj@20217
   671
              ()
webertj@20217
   672
            else let
webertj@20276
   673
              (* invent names for bound variables that are new, i.e. in Ts,  *)
webertj@20276
   674
              (* but not in params; we assume that Ts still contains (map    *)
webertj@20276
   675
              (* snd params) as a suffix                                     *)
webertj@20217
   676
              val new_count = length Ts - length params - 1
webertj@20217
   677
              val new_names = map Name.bound (0 upto new_count)
webertj@20217
   678
              val params'   = (new_names @ map fst params) ~~ Ts
webertj@20217
   679
            in
webertj@20217
   680
              trace_ex (sg, params', atoms, discr initems, n, hist)
webertj@20217
   681
            end; NONE)
nipkow@13498
   682
    end
skalberg@15531
   683
    | refute [] js = SOME js
nipkow@13498
   684
in refute end;
nipkow@5982
   685
webertj@20276
   686
fun refute (sg : theory) (params : (string * Term.typ) list) (show_ex : bool)
webertj@20433
   687
           (do_pre : bool) (terms : term list) : injust list option =
webertj@20433
   688
  refutes sg params show_ex (split_items sg do_pre (map snd params, terms)) [];
webertj@20254
   689
haftmann@22950
   690
fun count P xs = length (filter P xs);
webertj@20254
   691
webertj@20254
   692
(* The limit on the number of ~= allowed.
webertj@20254
   693
   Because each ~= is split into two cases, this can lead to an explosion.
webertj@20254
   694
*)
webertj@20254
   695
val fast_arith_neq_limit = ref 9;
webertj@20254
   696
webertj@20276
   697
fun prove (sg : theory) (params : (string * Term.typ) list) (show_ex : bool)
webertj@20433
   698
          (do_pre : bool) (Hs : term list) (concl : term) : injust list option =
webertj@20254
   699
  let
webertj@20254
   700
    (* append the negated conclusion to 'Hs' -- this corresponds to     *)
webertj@20254
   701
    (* 'DETERM (resolve_tac [LA_Logic.notI, LA_Logic.ccontr] i)' at the *)
webertj@20254
   702
    (* theorem/tactic level                                             *)
webertj@20254
   703
    val Hs' = Hs @ [LA_Logic.neg_prop concl]
webertj@20254
   704
    fun is_neq NONE                 = false
webertj@20254
   705
      | is_neq (SOME (_,_,r,_,_,_)) = (r = "~=")
webertj@20254
   706
  in
webertj@20254
   707
    trace_msg "prove";
webertj@20254
   708
    if count is_neq (map (LA_Data.decomp sg) Hs')
webertj@20254
   709
      > !fast_arith_neq_limit then (
webertj@20268
   710
      trace_msg ("fast_arith_neq_limit exceeded (current value is " ^
webertj@20268
   711
                   string_of_int (!fast_arith_neq_limit) ^ ")");
webertj@20254
   712
      NONE
webertj@20254
   713
    ) else
webertj@20433
   714
      refute sg params show_ex do_pre Hs'
webertj@20254
   715
  end;
webertj@20217
   716
wenzelm@22846
   717
fun refute_tac ss (i, justs) =
nipkow@6074
   718
  fn state =>
webertj@20268
   719
    let val _ = trace_thm ("refute_tac (on subgoal " ^ Int.toString i ^ ", with " ^
webertj@20268
   720
                             Int.toString (length justs) ^ " justification(s)):") state
webertj@20217
   721
        val sg          = theory_of_thm state
webertj@20217
   722
        val {neqE, ...} = Data.get sg
webertj@20217
   723
        fun just1 j =
webertj@20268
   724
          (* eliminate inequalities *)
webertj@20268
   725
          REPEAT_DETERM (eresolve_tac neqE i) THEN
webertj@20276
   726
            PRIMITIVE (trace_thm "State after neqE:") THEN
webertj@20268
   727
            (* use theorems generated from the actual justifications *)
webertj@20268
   728
            METAHYPS (fn asms => rtac (mkthm (sg, ss) asms j) 1) i
webertj@20268
   729
    in (* rewrite "[| A1; ...; An |] ==> B" to "[| A1; ...; An; ~B |] ==> False" *)
webertj@20268
   730
       DETERM (resolve_tac [LA_Logic.notI, LA_Logic.ccontr] i) THEN
webertj@20268
   731
       (* user-defined preprocessing of the subgoal *)
webertj@20268
   732
       DETERM (LA_Data.pre_tac i) THEN
webertj@20217
   733
       PRIMITIVE (trace_thm "State after pre_tac:") THEN
webertj@20268
   734
       (* prove every resulting subgoal, using its justification *)
webertj@20268
   735
       EVERY (map just1 justs)
webertj@20217
   736
    end  state;
nipkow@6074
   737
nipkow@5982
   738
(*
nipkow@5982
   739
Fast but very incomplete decider. Only premises and conclusions
nipkow@5982
   740
that are already (negated) (in)equations are taken into account.
nipkow@5982
   741
*)
webertj@20268
   742
fun simpset_lin_arith_tac (ss : simpset) (show_ex : bool) (i : int) (st : thm) =
webertj@20268
   743
  SUBGOAL (fn (A,_) =>
webertj@20217
   744
  let val params = rev (Logic.strip_params A)
webertj@20217
   745
      val Hs     = Logic.strip_assums_hyp A
webertj@20217
   746
      val concl  = Logic.strip_assums_concl A
nipkow@12932
   747
  in trace_thm ("Trying to refute subgoal " ^ string_of_int i) st;
wenzelm@22578
   748
     case prove (Thm.theory_of_thm st) params show_ex true Hs concl of
skalberg@15531
   749
       NONE => (trace_msg "Refutation failed."; no_tac)
webertj@20217
   750
     | SOME js => (trace_msg "Refutation succeeded."; refute_tac ss (i, js))
wenzelm@9420
   751
  end) i st;
nipkow@5982
   752
webertj@20268
   753
fun lin_arith_tac (show_ex : bool) (i : int) (st : thm) =
webertj@20276
   754
  simpset_lin_arith_tac
webertj@20276
   755
    (Simplifier.theory_context (Thm.theory_of_thm st) Simplifier.empty_ss)
webertj@20217
   756
    show_ex i st;
wenzelm@17613
   757
webertj@20268
   758
fun cut_lin_arith_tac (ss : simpset) (i : int) =
wenzelm@17613
   759
  cut_facts_tac (Simplifier.prems_of_ss ss) i THEN
wenzelm@17613
   760
  simpset_lin_arith_tac ss false i;
nipkow@5982
   761
nipkow@13186
   762
(** Forward proof from theorems **)
nipkow@13186
   763
webertj@20433
   764
(* More tricky code. Needs to arrange the proofs of the multiple cases (due
webertj@20433
   765
to splits of ~= premises) such that it coincides with the order of the cases
webertj@20433
   766
generated by function split_items. *)
webertj@20433
   767
webertj@20433
   768
datatype splittree = Tip of thm list
webertj@20433
   769
                   | Spl of thm * cterm * splittree * cterm * splittree;
webertj@20433
   770
webertj@20433
   771
(* "(ct1 ==> ?R) ==> (ct2 ==> ?R) ==> ?R" is taken to (ct1, ct2) *)
webertj@20433
   772
webertj@20433
   773
fun extract (imp : cterm) : cterm * cterm =
webertj@20433
   774
let val (Il, r)    = Thm.dest_comb imp
webertj@20433
   775
    val (_, imp1)  = Thm.dest_comb Il
webertj@20433
   776
    val (Ict1, _)  = Thm.dest_comb imp1
webertj@20433
   777
    val (_, ct1)   = Thm.dest_comb Ict1
webertj@20433
   778
    val (Ir, _)    = Thm.dest_comb r
webertj@20433
   779
    val (_, Ict2r) = Thm.dest_comb Ir
webertj@20433
   780
    val (Ict2, _)  = Thm.dest_comb Ict2r
webertj@20433
   781
    val (_, ct2)   = Thm.dest_comb Ict2
webertj@20433
   782
in (ct1, ct2) end;
webertj@20433
   783
webertj@20433
   784
fun splitasms (sg : theory) (asms : thm list) : splittree =
webertj@20433
   785
let val {neqE, ...} = Data.get sg
webertj@20433
   786
    fun elim_neq (asms', []) = Tip (rev asms')
webertj@20433
   787
      | elim_neq (asms', asm::asms) =
webertj@20433
   788
      (case get_first (fn th => SOME (asm COMP th) handle THM _ => NONE) neqE of
webertj@20433
   789
        SOME spl =>
webertj@20433
   790
          let val (ct1, ct2) = extract (cprop_of spl)
webertj@20433
   791
              val thm1 = assume ct1
webertj@20433
   792
              val thm2 = assume ct2
webertj@20433
   793
          in Spl (spl, ct1, elim_neq (asms', asms@[thm1]), ct2, elim_neq (asms', asms@[thm2]))
webertj@20433
   794
          end
webertj@20433
   795
      | NONE => elim_neq (asm::asms', asms))
webertj@20433
   796
in elim_neq ([], asms) end;
webertj@20433
   797
webertj@20433
   798
fun fwdproof (ctxt : theory * simpset) (Tip asms : splittree) (j::js : injust list) =
webertj@20433
   799
    (mkthm ctxt asms j, js)
webertj@20433
   800
  | fwdproof ctxt (Spl (thm, ct1, tree1, ct2, tree2)) js =
webertj@20433
   801
    let val (thm1, js1) = fwdproof ctxt tree1 js
webertj@20433
   802
        val (thm2, js2) = fwdproof ctxt tree2 js1
webertj@20433
   803
        val thm1' = implies_intr ct1 thm1
webertj@20433
   804
        val thm2' = implies_intr ct2 thm2
webertj@20433
   805
    in (thm2' COMP (thm1' COMP thm), js2) end;
webertj@20433
   806
(* needs handle THM _ => NONE ? *)
webertj@20433
   807
webertj@20268
   808
fun prover (ctxt as (sg, ss)) thms (Tconcl : term) (js : injust list) (pos : bool) : thm option =
webertj@20254
   809
let
webertj@20433
   810
(* vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv *)
webertj@20433
   811
(* Use this code instead if lin_arith_prover calls prove with do_pre set to true *)
webertj@20433
   812
(* but beware: this can be a significant performance issue.                      *)
webertj@20217
   813
    (* There is no "forward version" of 'pre_tac'.  Therefore we combine the     *)
webertj@20217
   814
    (* available theorems into a single proof state and perform "backward proof" *)
webertj@20217
   815
    (* using 'refute_tac'.                                                       *)
webertj@20433
   816
(*
webertj@20217
   817
    val Hs    = map prop_of thms
webertj@20217
   818
    val Prop  = fold (curry Logic.mk_implies) (rev Hs) Tconcl
webertj@20217
   819
    val cProp = cterm_of sg Prop
webertj@20217
   820
    val concl = Goal.init cProp
webertj@20217
   821
                  |> refute_tac ss (1, js)
webertj@20217
   822
                  |> Seq.hd
webertj@20217
   823
                  |> Goal.finish
webertj@20217
   824
                  |> fold (fn thA => fn thAB => implies_elim thAB thA) thms
webertj@20433
   825
*)
webertj@20433
   826
(* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ *)
webertj@20433
   827
    val nTconcl       = LA_Logic.neg_prop Tconcl
webertj@20433
   828
    val cnTconcl      = cterm_of sg nTconcl
webertj@20433
   829
    val nTconclthm    = assume cnTconcl
webertj@20433
   830
    val tree          = splitasms sg (thms @ [nTconclthm])
webertj@20433
   831
    val (Falsethm, _) = fwdproof ctxt tree js
webertj@20433
   832
    val contr         = if pos then LA_Logic.ccontr else LA_Logic.notI
webertj@20433
   833
    val concl         = implies_intr cnTconcl Falsethm COMP contr
webertj@20217
   834
in SOME (trace_thm "Proved by lin. arith. prover:"
webertj@20217
   835
          (LA_Logic.mk_Eq concl)) end
nipkow@13186
   836
(* in case concl contains ?-var, which makes assume fail: *)
skalberg@15531
   837
handle THM _ => NONE;
nipkow@13186
   838
nipkow@13186
   839
(* PRE: concl is not negated!
nipkow@13186
   840
   This assumption is OK because
nipkow@13186
   841
   1. lin_arith_prover tries both to prove and disprove concl and
nipkow@13186
   842
   2. lin_arith_prover is applied by the simplifier which
nipkow@13186
   843
      dives into terms and will thus try the non-negated concl anyway.
nipkow@13186
   844
*)
webertj@20217
   845
webertj@20268
   846
fun lin_arith_prover sg ss (concl : term) : thm option =
webertj@20217
   847
let val thms = List.concat (map LA_Logic.atomize (prems_of_ss ss));
webertj@20217
   848
    val Hs = map prop_of thms
nipkow@6102
   849
    val Tconcl = LA_Logic.mk_Trueprop concl
webertj@20217
   850
(*
webertj@20217
   851
    val _ = trace_msg "lin_arith_prover"
webertj@20217
   852
    val _ = map (trace_thm "thms:") thms
webertj@20217
   853
    val _ = trace_msg ("concl:" ^ Sign.string_of_term sg concl)
webertj@20217
   854
*)
webertj@20433
   855
in case prove sg [] false false Hs Tconcl of (* concl provable? *)
wenzelm@17515
   856
     SOME js => prover (sg, ss) thms Tconcl js true
skalberg@15531
   857
   | NONE => let val nTconcl = LA_Logic.neg_prop Tconcl
webertj@20433
   858
          in case prove sg [] false false Hs nTconcl of (* ~concl provable? *)
wenzelm@17515
   859
               SOME js => prover (sg, ss) thms nTconcl js false
skalberg@15531
   860
             | NONE => NONE
nipkow@6079
   861
          end
nipkow@5982
   862
end;
nipkow@6074
   863
nipkow@6074
   864
end;