src/Provers/Arith/fast_lin_arith.ML
author webertj
Tue Aug 01 14:58:43 2006 +0200 (2006-08-01)
changeset 20276 d94dc40673b1
parent 20268 1fe9aed8fcac
child 20280 ad9fbbd01535
permissions -rw-r--r--
possible disagreement between proof search and proof reconstruction when eliminating inequalities over different types fixed
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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 setup: theory -> theory
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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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(* data kind 'Provers/fast_lin_arith' *)
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structure Data = TheoryDataFun
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(struct
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  val name = "Provers/fast_lin_arith";
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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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  fun print _ _ = ();
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end);
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val map_data = Data.map;
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val setup = Data.init;
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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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fun el 0 (h::_) = h
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  | el n (_::t) = el (n - 1) t
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  | el _ _  = sys_error "el";
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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(ineqs,Lineq(i,Le,cs,_)) = (i,true,cs)::ineqs
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  | elim_eqns(ineqs,Lineq(i,Eq,cs,_)) = (i,true,cs)::(~i,true,map ~ cs)::ineqs
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  | elim_eqns(ineqs,Lineq(i,Lt,cs,_)) = (i,false,cs)::ineqs;
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(* PRE: ex[v] must be 0! *)
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fun eval (ex:Rat.rat list) v (a:IntInf.int,le,cs:IntInf.int list) =
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  let val rs = map Rat.rat_of_intinf cs
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      val rsum = Library.foldl Rat.add (Rat.zero, map Rat.mult (rs ~~ ex))
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  in (Rat.mult (Rat.add(Rat.rat_of_intinf a,Rat.neg rsum), Rat.inv(el v rs)), le) end;
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(* If el v rs < 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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  if r=s then (r, (not ler) andalso (not les)) else if Rat.le(r,s) then x else y;
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fun ratrelmax2(x as (r,ler),y as (s,les)) =
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  if r=s then (r,ler andalso les) else if Rat.le(r,s) then y else 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 val (p,q) = Rat.quotient_of_rat r
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      val nth = Rat.inv(Rat.rat_of_intinf 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.rat_of_int 2));
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fun choose2 d ((lb, exactl), (ub, exactu)) =
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  if Rat.le (lb, Rat.zero) andalso (lb <> Rat.zero orelse exactl) andalso
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     Rat.le (Rat.zero, ub) andalso (ub <> Rat.zero orelse exactu)
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  then Rat.zero else
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  if not d
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  then (if Rat.ge0 lb
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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 Rat.ge0 lb then let val lb' = Rat.roundup lb
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                    in if Rat.le (lb', ub) then lb' else raise NoEx end
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               else let val ub' = Rat.rounddown ub
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                    in if Rat.le (lb, ub') then ub' else raise NoEx end;
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fun findex1 discr (ex, (v, lineqs)) =
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  let val nz = List.filter (fn (Lineq(_,_,cs,_)) => el v cs <> 0) lineqs;
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      val ineqs = Library.foldl elim_eqns ([],nz)
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      val (ge,le) = List.partition (fn (_,_,cs) => el v cs > 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_update (v, choose2 (nth discr v) (lb, ub)) ex end;
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fun findex discr = Library.foldl (findex1 discr);
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fun elim1 v x =
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  map (fn (a,le,bs) => (Rat.add (a, Rat.neg (Rat.mult (el v bs, x))), le,
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                        nth_update (v, Rat.zero) bs));
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fun single_var v (_,_,cs) = (filter_out (equal Rat.zero) cs = [el v cs]);
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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 (equal Rat.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 equal Rat.zero) cs
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           val d = nth discr v
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           val pos = Rat.ge0(el v cs)
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           val sv = List.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(el v bs)),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_update (v, 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 = Library.foldl elim_eqns ([],lineqs)
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      val rineqs = map (fn (a,le,cs) => (Rat.rat_of_intinf a, le, map Rat.rat_of_intinf 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 = el v l1 and c2 = el v l2
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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)
nipkow@5982
   317
                    then (~n1,~n2) else (n1,n2)
nipkow@5982
   318
  in add_ineq (multiply_ineq n1 i1) (multiply_ineq n2 i2) end;
nipkow@5982
   319
nipkow@5982
   320
(* ------------------------------------------------------------------------- *)
nipkow@5982
   321
(* The main refutation-finding code.                                         *)
nipkow@5982
   322
(* ------------------------------------------------------------------------- *)
nipkow@5982
   323
nipkow@5982
   324
fun is_trivial (Lineq(_,_,l,_)) = forall (fn i => i=0) l;
nipkow@5982
   325
nipkow@5982
   326
fun is_answer (ans as Lineq(k,ty,l,_)) =
nipkow@5982
   327
  case ty  of Eq => k <> 0 | Le => k > 0 | Lt => k >= 0;
nipkow@5982
   328
nipkow@16358
   329
fun calc_blowup (l:IntInf.int list) =
haftmann@17496
   330
  let val (p,n) = List.partition (curry (op <) 0) (List.filter (curry (op <>) 0) l)
nipkow@5982
   331
  in (length p) * (length n) end;
nipkow@5982
   332
nipkow@5982
   333
(* ------------------------------------------------------------------------- *)
nipkow@5982
   334
(* Main elimination code:                                                    *)
nipkow@5982
   335
(*                                                                           *)
nipkow@5982
   336
(* (1) Looks for immediate solutions (false assertions with no variables).   *)
nipkow@5982
   337
(*                                                                           *)
nipkow@5982
   338
(* (2) If there are any equations, picks a variable with the lowest absolute *)
nipkow@5982
   339
(* coefficient in any of them, and uses it to eliminate.                     *)
nipkow@5982
   340
(*                                                                           *)
nipkow@5982
   341
(* (3) Otherwise, chooses a variable in the inequality to minimize the       *)
nipkow@5982
   342
(* blowup (number of consequences generated) and eliminates it.              *)
nipkow@5982
   343
(* ------------------------------------------------------------------------- *)
nipkow@5982
   344
nipkow@5982
   345
fun allpairs f xs ys =
webertj@20217
   346
  List.concat (map (fn x => map (fn y => f x y) ys) xs);
nipkow@5982
   347
nipkow@5982
   348
fun extract_first p =
skalberg@15531
   349
  let fun extract xs (y::ys) = if p y then (SOME y,xs@ys)
nipkow@5982
   350
                               else extract (y::xs) ys
skalberg@15531
   351
        | extract xs []      = (NONE,xs)
nipkow@5982
   352
  in extract [] end;
nipkow@5982
   353
nipkow@6056
   354
fun print_ineqs ineqs =
paulson@9073
   355
  if !trace then
wenzelm@12262
   356
     tracing(cat_lines(""::map (fn Lineq(c,t,l,_) =>
nipkow@16358
   357
       IntInf.toString c ^
paulson@9073
   358
       (case t of Eq => " =  " | Lt=> " <  " | Le => " <= ") ^
nipkow@16358
   359
       commas(map IntInf.toString l)) ineqs))
paulson@9073
   360
  else ();
nipkow@6056
   361
nipkow@13498
   362
type history = (int * lineq list) list;
nipkow@13498
   363
datatype result = Success of injust | Failure of history;
nipkow@13498
   364
webertj@20217
   365
fun elim (ineqs, hist) =
webertj@20217
   366
  let val dummy = print_ineqs ineqs
webertj@20217
   367
      val (triv, nontriv) = List.partition is_trivial ineqs in
webertj@20217
   368
  if not (null triv)
nipkow@13186
   369
  then case Library.find_first is_answer triv of
webertj@20217
   370
         NONE => elim (nontriv, hist)
skalberg@15531
   371
       | SOME(Lineq(_,_,_,j)) => Success j
nipkow@5982
   372
  else
webertj@20217
   373
  if null nontriv then Failure hist
nipkow@13498
   374
  else
webertj@20217
   375
  let val (eqs, noneqs) = List.partition (fn (Lineq(_,ty,_,_)) => ty=Eq) nontriv in
webertj@20217
   376
  if not (null eqs) then
skalberg@15570
   377
     let val clist = Library.foldl (fn (cs,Lineq(_,_,l,_)) => l union cs) ([],eqs)
nipkow@16358
   378
         val sclist = sort (fn (x,y) => IntInf.compare(abs(x),abs(y)))
skalberg@15570
   379
                           (List.filter (fn i => i<>0) clist)
nipkow@5982
   380
         val c = hd sclist
skalberg@15531
   381
         val (SOME(eq as Lineq(_,_,ceq,_)),othereqs) =
nipkow@5982
   382
               extract_first (fn Lineq(_,_,l,_) => c mem l) eqs
webertj@20217
   383
         val v = find_index_eq c ceq
skalberg@15570
   384
         val (ioth,roth) = List.partition (fn (Lineq(_,_,l,_)) => el v l = 0)
nipkow@5982
   385
                                     (othereqs @ noneqs)
nipkow@5982
   386
         val others = map (elim_var v eq) roth @ ioth
nipkow@13498
   387
     in elim(others,(v,nontriv)::hist) end
nipkow@5982
   388
  else
nipkow@5982
   389
  let val lists = map (fn (Lineq(_,_,l,_)) => l) noneqs
nipkow@5982
   390
      val numlist = 0 upto (length(hd lists) - 1)
nipkow@5982
   391
      val coeffs = map (fn i => map (el i) lists) numlist
nipkow@5982
   392
      val blows = map calc_blowup coeffs
nipkow@5982
   393
      val iblows = blows ~~ numlist
skalberg@15570
   394
      val nziblows = List.filter (fn (i,_) => i<>0) iblows
nipkow@13498
   395
  in if null nziblows then Failure((~1,nontriv)::hist)
nipkow@13498
   396
     else
nipkow@5982
   397
     let val (c,v) = hd(sort (fn (x,y) => int_ord(fst(x),fst(y))) nziblows)
skalberg@15570
   398
         val (no,yes) = List.partition (fn (Lineq(_,_,l,_)) => el v l = 0) ineqs
skalberg@15570
   399
         val (pos,neg) = List.partition(fn (Lineq(_,_,l,_)) => el v l > 0) yes
nipkow@13498
   400
     in elim(no @ allpairs (elim_var v) pos neg, (v,nontriv)::hist) end
nipkow@5982
   401
  end
nipkow@5982
   402
  end
nipkow@5982
   403
  end;
nipkow@5982
   404
nipkow@5982
   405
(* ------------------------------------------------------------------------- *)
nipkow@5982
   406
(* Translate back a proof.                                                   *)
nipkow@5982
   407
(* ------------------------------------------------------------------------- *)
nipkow@5982
   408
webertj@20268
   409
fun trace_thm (msg : string) (th : thm) : thm =
webertj@20217
   410
    (if !trace then (tracing msg; tracing (Display.string_of_thm th)) else (); th);
paulson@9073
   411
webertj@20268
   412
fun trace_msg (msg : string) : unit =
wenzelm@12262
   413
    if !trace then tracing msg else ();
paulson@9073
   414
nipkow@13498
   415
(* FIXME OPTIMIZE!!!! (partly done already)
nipkow@6056
   416
   Addition/Multiplication need i*t representation rather than t+t+...
nipkow@10691
   417
   Get rid of Mulitplied(2). For Nat LA_Data.number_of should return Suc^n
nipkow@10691
   418
   because Numerals are not known early enough.
nipkow@6056
   419
nipkow@6056
   420
Simplification may detect a contradiction 'prematurely' due to type
nipkow@6056
   421
information: n+1 <= 0 is simplified to False and does not need to be crossed
nipkow@6056
   422
with 0 <= n.
nipkow@6056
   423
*)
nipkow@6056
   424
local
nipkow@6056
   425
 exception FalseE of thm
nipkow@6056
   426
in
webertj@20268
   427
fun mkthm (sg:theory, ss:simpset) (asms:thm list) (just:injust) : thm =
nipkow@15922
   428
  let val {add_mono_thms, mult_mono_thms, inj_thms, lessD, simpset, ...} =
wenzelm@16458
   429
          Data.get sg;
wenzelm@17877
   430
      val simpset' = Simplifier.inherit_context ss simpset;
webertj@20217
   431
      val atoms = Library.foldl (fn (ats, (lhs,_,_,rhs,_,_)) =>
nipkow@6056
   432
                            map fst lhs  union  (map fst rhs  union  ats))
webertj@20217
   433
                        ([], List.mapPartial (fn thm => if Thm.no_prems thm
webertj@20217
   434
                                              then LA_Data.decomp sg (concl_of thm)
webertj@20217
   435
                                              else NONE) asms)
nipkow@6056
   436
nipkow@10575
   437
      fun add2 thm1 thm2 =
nipkow@6102
   438
        let val conj = thm1 RS (thm2 RS LA_Logic.conjI)
skalberg@15531
   439
        in get_first (fn th => SOME(conj RS th) handle THM _ => NONE) add_mono_thms
nipkow@5982
   440
        end;
skalberg@15531
   441
      fun try_add [] _ = NONE
nipkow@10575
   442
        | try_add (thm1::thm1s) thm2 = case add2 thm1 thm2 of
skalberg@15531
   443
             NONE => try_add thm1s thm2 | some => some;
nipkow@10575
   444
nipkow@10575
   445
      fun addthms thm1 thm2 =
nipkow@10575
   446
        case add2 thm1 thm2 of
skalberg@15531
   447
          NONE => (case try_add ([thm1] RL inj_thms) thm2 of
webertj@20217
   448
                     NONE => ( the (try_add ([thm2] RL inj_thms) thm1)
wenzelm@15660
   449
                               handle Option =>
nipkow@14360
   450
                               (trace_thm "" thm1; trace_thm "" thm2;
webertj@20217
   451
                                sys_error "Lin.arith. failed to add thms")
webertj@20217
   452
                             )
skalberg@15531
   453
                   | SOME thm => thm)
skalberg@15531
   454
        | SOME thm => thm;
nipkow@10575
   455
nipkow@5982
   456
      fun multn(n,thm) =
nipkow@5982
   457
        let fun mul(i,th) = if i=1 then th else mul(i-1, addthms thm th)
nipkow@6102
   458
        in if n < 0 then mul(~n,thm) RS LA_Logic.sym else mul(n,thm) end;
webertj@20217
   459
nipkow@15184
   460
      fun multn2(n,thm) =
skalberg@15531
   461
        let val SOME(mth) =
skalberg@15531
   462
              get_first (fn th => SOME(thm RS th) handle THM _ => NONE) mult_mono_thms
nipkow@15184
   463
            fun cvar(th,_ $ (_ $ _ $ var)) = cterm_of (#sign(rep_thm th)) var;
nipkow@15184
   464
            val cv = cvar(mth, hd(prems_of mth));
nipkow@15184
   465
            val ct = cterm_of sg (LA_Data.number_of(n,#T(rep_cterm cv)))
nipkow@15184
   466
        in instantiate ([],[(cv,ct)]) mth end
nipkow@10691
   467
nipkow@6056
   468
      fun simp thm =
wenzelm@17515
   469
        let val thm' = trace_thm "Simplified:" (full_simplify simpset' thm)
nipkow@6102
   470
        in if LA_Logic.is_False thm' then raise FalseE thm' else thm' end
nipkow@6056
   471
webertj@20276
   472
      fun mk (Asm i)              = trace_thm ("Asm " ^ Int.toString i) (nth asms i)
webertj@20276
   473
        | mk (Nat i)              = trace_thm ("Nat " ^ Int.toString i) (LA_Logic.mk_nat_thm sg (nth atoms i))
webertj@20254
   474
        | mk (LessD j)            = trace_thm "L" (hd ([mk j] RL lessD))
webertj@20254
   475
        | mk (NotLeD j)           = trace_thm "NLe" (mk j RS LA_Logic.not_leD)
webertj@20254
   476
        | mk (NotLeDD j)          = trace_thm "NLeD" (hd ([mk j RS LA_Logic.not_leD] RL lessD))
webertj@20254
   477
        | mk (NotLessD j)         = trace_thm "NL" (mk j RS LA_Logic.not_lessD)
webertj@20254
   478
        | mk (Added (j1, j2))     = simp (trace_thm "+" (addthms (mk j1) (mk j2)))
webertj@20254
   479
        | mk (Multiplied (n, j))  = (trace_msg ("*" ^ IntInf.toString n); trace_thm "*" (multn (n, mk j)))
webertj@20254
   480
        | mk (Multiplied2 (n, j)) = simp (trace_msg ("**" ^ IntInf.toString n); trace_thm "**" (multn2 (n, mk j)))
nipkow@5982
   481
paulson@9073
   482
  in trace_msg "mkthm";
nipkow@12932
   483
     let val thm = trace_thm "Final thm:" (mk just)
wenzelm@17515
   484
     in let val fls = simplify simpset' thm
nipkow@13186
   485
        in trace_thm "After simplification:" fls;
nipkow@13186
   486
           if LA_Logic.is_False fls then fls
nipkow@13186
   487
           else
webertj@20217
   488
            (tracing "Assumptions:"; List.app (tracing o Display.string_of_thm) asms;
webertj@20217
   489
             tracing "Proved:"; tracing (Display.string_of_thm fls);
nipkow@13186
   490
             warning "Linear arithmetic should have refuted the assumptions.\n\
nipkow@13186
   491
                     \Please inform Tobias Nipkow (nipkow@in.tum.de).";
nipkow@13186
   492
             fls)
nipkow@12932
   493
        end
webertj@20217
   494
     end handle FalseE thm => trace_thm "False reached early:" thm
nipkow@12932
   495
  end
nipkow@6056
   496
end;
nipkow@5982
   497
nipkow@16358
   498
fun coeff poly atom : IntInf.int =
haftmann@17325
   499
  AList.lookup (op =) poly atom |> the_default 0;
nipkow@5982
   500
webertj@20276
   501
fun lcms (is : int list) : int = Library.foldl lcm (1, is);
nipkow@10691
   502
nipkow@10691
   503
fun integ(rlhs,r,rel,rrhs,s,d) =
haftmann@17951
   504
let val (rn,rd) = Rat.quotient_of_rat r and (sn,sd) = Rat.quotient_of_rat s
haftmann@17951
   505
    val m = lcms(map (abs o snd o Rat.quotient_of_rat) (r :: s :: map snd rlhs @ map snd rrhs))
paulson@15965
   506
    fun mult(t,r) = 
haftmann@17951
   507
        let val (i,j) = Rat.quotient_of_rat r
paulson@15965
   508
        in (t,i * (m div j)) end
nipkow@12932
   509
in (m,(map mult rlhs, rn*(m div rd), rel, map mult rrhs, sn*(m div sd), d)) end
nipkow@10691
   510
nipkow@13498
   511
fun mklineq n atoms =
webertj@20217
   512
  fn (item, k) =>
webertj@20217
   513
  let val (m, (lhs,i,rel,rhs,j,discrete)) = integ item
nipkow@13498
   514
      val lhsa = map (coeff lhs) atoms
nipkow@13498
   515
      and rhsa = map (coeff rhs) atoms
haftmann@18330
   516
      val diff = map2 (curry (op -)) rhsa lhsa
nipkow@13498
   517
      val c = i-j
nipkow@13498
   518
      val just = Asm k
nipkow@13498
   519
      fun lineq(c,le,cs,j) = Lineq(c,le,cs, if m=1 then j else Multiplied2(m,j))
nipkow@13498
   520
  in case rel of
nipkow@13498
   521
      "<="   => lineq(c,Le,diff,just)
nipkow@13498
   522
     | "~<=" => if discrete
nipkow@13498
   523
                then lineq(1-c,Le,map (op ~) diff,NotLeDD(just))
nipkow@13498
   524
                else lineq(~c,Lt,map (op ~) diff,NotLeD(just))
nipkow@13498
   525
     | "<"   => if discrete
nipkow@13498
   526
                then lineq(c+1,Le,diff,LessD(just))
nipkow@13498
   527
                else lineq(c,Lt,diff,just)
nipkow@13498
   528
     | "~<"  => lineq(~c,Le,map (op~) diff,NotLessD(just))
nipkow@13498
   529
     | "="   => lineq(c,Eq,diff,just)
nipkow@13498
   530
     | _     => sys_error("mklineq" ^ rel)   
nipkow@5982
   531
  end;
nipkow@5982
   532
nipkow@13498
   533
(* ------------------------------------------------------------------------- *)
nipkow@13498
   534
(* Print (counter) example                                                   *)
nipkow@13498
   535
(* ------------------------------------------------------------------------- *)
nipkow@13498
   536
nipkow@13498
   537
fun print_atom((a,d),r) =
haftmann@17951
   538
  let val (p,q) = Rat.quotient_of_rat r
paulson@15965
   539
      val s = if d then IntInf.toString p else
nipkow@13498
   540
              if p = 0 then "0"
paulson@15965
   541
              else IntInf.toString p ^ "/" ^ IntInf.toString q
nipkow@13498
   542
  in a ^ " = " ^ s end;
nipkow@13498
   543
wenzelm@19049
   544
fun produce_ex sds =
haftmann@17496
   545
  curry (op ~~) sds
haftmann@17496
   546
  #> map print_atom
haftmann@17496
   547
  #> commas
webertj@20217
   548
  #> curry (op ^) "Counter example (possibly spurious):\n";
nipkow@13498
   549
webertj@20217
   550
fun trace_ex (sg, params, atoms, discr, n, hist : history) =
webertj@20217
   551
  case hist of
webertj@20217
   552
    [] => ()
webertj@20217
   553
  | (v, lineqs) :: hist' =>
webertj@20217
   554
    let val frees = map Free params
webertj@20217
   555
        fun s_of_t t = Sign.string_of_term sg (subst_bounds (frees, t))
webertj@20217
   556
        val start = if v = ~1 then (findex0 discr n lineqs, hist')
webertj@20217
   557
                    else (replicate n Rat.zero, hist)
webertj@20217
   558
        val ex = SOME (produce_ex ((map s_of_t atoms) ~~ discr) (findex discr start))
webertj@20217
   559
          handle NoEx => NONE
webertj@20217
   560
    in
webertj@20217
   561
      case ex of
webertj@20217
   562
        SOME s => (warning "arith failed - see trace for a counter example"; tracing s)
webertj@20217
   563
      | NONE => warning "arith failed"
webertj@20217
   564
    end;
nipkow@13498
   565
webertj@20217
   566
(* ------------------------------------------------------------------------- *)
webertj@20217
   567
webertj@20268
   568
fun mknat (pTs : typ list) (ixs : int list) (atom : term, i : int) : lineq option =
webertj@20217
   569
  if LA_Logic.is_nat (pTs, atom)
nipkow@6056
   570
  then let val l = map (fn j => if j=i then 1 else 0) ixs
webertj@20217
   571
       in SOME (Lineq (0, Le, l, Nat i)) end
webertj@20217
   572
  else NONE;
nipkow@6056
   573
nipkow@13186
   574
(* This code is tricky. It takes a list of premises in the order they occur
skalberg@15531
   575
in the subgoal. Numerical premises are coded as SOME(tuple), non-numerical
skalberg@15531
   576
ones as NONE. Going through the premises, each numeric one is converted into
nipkow@13186
   577
a Lineq. The tricky bit is to convert ~= which is split into two cases < and
nipkow@13498
   578
>. Thus split_items returns a list of equation systems. This may blow up if
nipkow@13186
   579
there are many ~=, but in practice it does not seem to happen. The really
nipkow@13186
   580
tricky bit is to arrange the order of the cases such that they coincide with
nipkow@13186
   581
the order in which the cases are in the end generated by the tactic that
nipkow@13186
   582
applies the generated refutation thms (see function 'refute_tac').
nipkow@13186
   583
nipkow@13186
   584
For variables n of type nat, a constraint 0 <= n is added.
nipkow@13186
   585
*)
webertj@20217
   586
webertj@20217
   587
(* FIXME: To optimize, the splitting of cases and the search for refutations *)
webertj@20276
   588
(*        could be intertwined: separate the first (fully split) case,       *)
webertj@20217
   589
(*        refute it, continue with splitting and refuting.  Terminate with   *)
webertj@20217
   590
(*        failure as soon as a case could not be refuted; i.e. delay further *)
webertj@20217
   591
(*        splitting until after a refutation for other cases has been found. *)
webertj@20217
   592
webertj@20276
   593
fun split_items sg (Ts : typ list, terms : term list) :
webertj@20276
   594
                (typ list * (LA_Data.decompT * int) list) list =
webertj@20276
   595
let
webertj@20217
   596
(*
webertj@20276
   597
  val _ = if !trace then
webertj@20276
   598
            trace_msg ("split_items: Ts    = " ^ string_of_list (Sign.string_of_typ sg) Ts ^ "\n" ^
webertj@20276
   599
                       "             terms = " ^ string_of_list (Sign.string_of_term sg) terms)
webertj@20276
   600
          else ()
webertj@20217
   601
*)
webertj@20276
   602
  (* splits inequalities '~=' into '<' and '>'; this corresponds to *)
webertj@20276
   603
  (* 'REPEAT_DETERM (eresolve_tac neqE i)' at the theorem/tactic    *)
webertj@20276
   604
  (* level                                                          *)
webertj@20276
   605
  (* FIXME: this is currently sensitive to the order of theorems in *)
webertj@20276
   606
  (*        neqE:  The theorem for type "nat" must come first.  A   *)
webertj@20276
   607
  (*        better (i.e. less likely to break when neqE changes)    *)
webertj@20276
   608
  (*        implementation should *test* which theorem from neqE    *)
webertj@20276
   609
  (*        can be applied, and split the premise accordingly.      *)
webertj@20276
   610
  fun elim_neq (ineqs : (LA_Data.decompT option * bool) list) :
webertj@20276
   611
               (LA_Data.decompT option * bool) list list =
webertj@20276
   612
  let
webertj@20276
   613
    fun elim_neq' nat_only ([] : (LA_Data.decompT option * bool) list) :
webertj@20276
   614
                  (LA_Data.decompT option * bool) list list =
webertj@20276
   615
          [[]]
webertj@20276
   616
      | elim_neq' nat_only ((NONE, is_nat) :: ineqs) =
webertj@20276
   617
          map (cons (NONE, is_nat)) (elim_neq' nat_only ineqs)
webertj@20276
   618
      | elim_neq' nat_only ((ineq as (SOME (l, i, rel, r, j, d), is_nat)) :: ineqs) =
webertj@20276
   619
          if rel = "~=" andalso (not nat_only orelse is_nat) then
webertj@20276
   620
            (* [| ?l ~= ?r; ?l < ?r ==> ?R; ?r < ?l ==> ?R |] ==> ?R *)
webertj@20276
   621
            elim_neq' nat_only (ineqs @ [(SOME (l, i, "<", r, j, d), is_nat)]) @
webertj@20276
   622
            elim_neq' nat_only (ineqs @ [(SOME (r, j, "<", l, i, d), is_nat)])
webertj@20276
   623
          else
webertj@20276
   624
            map (cons ineq) (elim_neq' nat_only ineqs)
webertj@20276
   625
  in
webertj@20276
   626
    ineqs |> elim_neq' true
webertj@20276
   627
          |> map (elim_neq' false)
webertj@20276
   628
          |> List.concat
webertj@20276
   629
  end
nipkow@13464
   630
webertj@20276
   631
  fun number_hyps _ []             = []
webertj@20276
   632
    | number_hyps n (NONE::xs)     = number_hyps (n+1) xs
webertj@20276
   633
    | number_hyps n ((SOME x)::xs) = (x, n) :: number_hyps (n+1) xs
webertj@20276
   634
webertj@20276
   635
  val result = (Ts, terms)
webertj@20276
   636
    |> (* user-defined preprocessing of the subgoal *)
webertj@20276
   637
       (* (typ list * term list) list *)
webertj@20276
   638
       LA_Data.pre_decomp sg
webertj@20276
   639
    |> (* compute the internal encoding of (in-)equalities *)
webertj@20276
   640
       (* (typ list * (LA_Data.decompT option * bool) list) list *)
webertj@20276
   641
       map (apsnd (map (fn t => (LA_Data.decomp sg t, LA_Data.domain_is_nat t))))
webertj@20276
   642
    |> (* splitting of inequalities *)
webertj@20276
   643
       (* (typ list * (LA_Data.decompT option * bool) list list) list *)
webertj@20276
   644
       map (apsnd elim_neq)
webertj@20276
   645
    |> (* combine the list of lists of subgoals into a single list *)
webertj@20276
   646
       map (fn (Ts, subgoals) => map (pair Ts o map fst) subgoals)
webertj@20276
   647
    |> List.concat
webertj@20276
   648
    |> (* numbering of hypotheses, ignoring irrelevant ones *)
webertj@20276
   649
       map (apsnd (number_hyps 0))
webertj@20217
   650
(*
webertj@20276
   651
  val _ = if !trace then
webertj@20276
   652
            trace_msg ("split_items: result has " ^ Int.toString (length result) ^
webertj@20276
   653
              " subgoal(s)" ^ "\n" ^ (cat_lines o fst) (fold_map (fn (Ts, items) => fn n =>
webertj@20276
   654
                ("  " ^ Int.toString n ^ ". Ts    = " ^
webertj@20276
   655
                   string_of_list (Sign.string_of_typ sg) Ts ^ "\n" ^
webertj@20276
   656
                 "     items = " ^ string_of_list (string_of_pair 
webertj@20276
   657
                   (fn (l, i, rel, r, j, d) => enclose "(" ")" (commas
webertj@20276
   658
                     [string_of_list
webertj@20276
   659
                        (string_of_pair (Sign.string_of_term sg) Rat.string_of_rat) l,
webertj@20276
   660
                      Rat.string_of_rat i,
webertj@20276
   661
                      rel,
webertj@20276
   662
                      string_of_list
webertj@20276
   663
                        (string_of_pair (Sign.string_of_term sg) Rat.string_of_rat) r,
webertj@20276
   664
                      Rat.string_of_rat j,
webertj@20276
   665
                      Bool.toString d]))
webertj@20276
   666
                   Int.toString) items, n+1)) result 1))
webertj@20276
   667
          else ()
webertj@20217
   668
*)
webertj@20276
   669
in result end;
nipkow@13464
   670
webertj@20268
   671
fun add_atoms (ats : term list, ((lhs,_,_,rhs,_,_) : LA_Data.decompT, _)) : term list =
webertj@20217
   672
    (map fst lhs) union ((map fst rhs) union ats);
webertj@20217
   673
webertj@20268
   674
fun add_datoms (dats : (bool * term) list, ((lhs,_,_,rhs,_,d) : LA_Data.decompT, _)) :
webertj@20268
   675
  (bool * term) list =
webertj@20268
   676
  (map (pair d o fst) lhs) union ((map (pair d o fst) rhs) union dats);
nipkow@13498
   677
webertj@20268
   678
fun discr (initems : (LA_Data.decompT * int) list) : bool list =
webertj@20268
   679
  map fst (Library.foldl add_datoms ([],initems));
webertj@20217
   680
webertj@20268
   681
fun refutes (sg : theory) (params : (string * typ) list) (show_ex : bool) :
webertj@20268
   682
  (typ list * (LA_Data.decompT * int) list) list -> injust list -> injust list option =
nipkow@13498
   683
let
webertj@20268
   684
  fun refute ((Ts : typ list, initems : (LA_Data.decompT * int) list)::initemss)
webertj@20268
   685
             (js : injust list) : injust list option =
webertj@20217
   686
    let val atoms = Library.foldl add_atoms ([], initems)
nipkow@13498
   687
        val n = length atoms
nipkow@13498
   688
        val mkleq = mklineq n atoms
nipkow@13498
   689
        val ixs = 0 upto (n-1)
nipkow@13498
   690
        val iatoms = atoms ~~ ixs
webertj@20217
   691
        val natlineqs = List.mapPartial (mknat Ts ixs) iatoms
nipkow@13498
   692
        val ineqs = map mkleq initems @ natlineqs
webertj@20217
   693
    in case elim (ineqs, []) of
webertj@20217
   694
         Success j =>
webertj@20268
   695
           (trace_msg ("Contradiction! (" ^ Int.toString (length js + 1) ^ ")");
webertj@20268
   696
            refute initemss (js@[j]))
webertj@20217
   697
       | Failure hist =>
webertj@20217
   698
           (if not show_ex then
webertj@20217
   699
              ()
webertj@20217
   700
            else let
webertj@20276
   701
              (* invent names for bound variables that are new, i.e. in Ts,  *)
webertj@20276
   702
              (* but not in params; we assume that Ts still contains (map    *)
webertj@20276
   703
              (* snd params) as a suffix                                     *)
webertj@20217
   704
              val new_count = length Ts - length params - 1
webertj@20217
   705
              val new_names = map Name.bound (0 upto new_count)
webertj@20217
   706
              val params'   = (new_names @ map fst params) ~~ Ts
webertj@20217
   707
            in
webertj@20217
   708
              trace_ex (sg, params', atoms, discr initems, n, hist)
webertj@20217
   709
            end; NONE)
nipkow@13498
   710
    end
skalberg@15531
   711
    | refute [] js = SOME js
nipkow@13498
   712
in refute end;
nipkow@5982
   713
webertj@20276
   714
fun refute (sg : theory) (params : (string * Term.typ) list) (show_ex : bool)
webertj@20276
   715
           (terms : term list) : injust list option =
webertj@20254
   716
  refutes sg params show_ex (split_items sg (map snd params, terms)) [];
webertj@20254
   717
webertj@20268
   718
fun count (P : 'a -> bool) (xs : 'a list) : int = length (List.filter P xs);
webertj@20254
   719
webertj@20254
   720
(* The limit on the number of ~= allowed.
webertj@20254
   721
   Because each ~= is split into two cases, this can lead to an explosion.
webertj@20254
   722
*)
webertj@20254
   723
val fast_arith_neq_limit = ref 9;
webertj@20254
   724
webertj@20276
   725
fun prove (sg : theory) (params : (string * Term.typ) list) (show_ex : bool)
webertj@20276
   726
          (Hs : term list) (concl : term) : injust list option =
webertj@20254
   727
  let
webertj@20254
   728
    (* append the negated conclusion to 'Hs' -- this corresponds to     *)
webertj@20254
   729
    (* 'DETERM (resolve_tac [LA_Logic.notI, LA_Logic.ccontr] i)' at the *)
webertj@20254
   730
    (* theorem/tactic level                                             *)
webertj@20254
   731
    val Hs' = Hs @ [LA_Logic.neg_prop concl]
webertj@20254
   732
    fun is_neq NONE                 = false
webertj@20254
   733
      | is_neq (SOME (_,_,r,_,_,_)) = (r = "~=")
webertj@20254
   734
  in
webertj@20254
   735
    trace_msg "prove";
webertj@20254
   736
    if count is_neq (map (LA_Data.decomp sg) Hs')
webertj@20254
   737
      > !fast_arith_neq_limit then (
webertj@20268
   738
      trace_msg ("fast_arith_neq_limit exceeded (current value is " ^
webertj@20268
   739
                   string_of_int (!fast_arith_neq_limit) ^ ")");
webertj@20254
   740
      NONE
webertj@20254
   741
    ) else
webertj@20254
   742
      refute sg params show_ex Hs'
webertj@20254
   743
  end;
webertj@20217
   744
webertj@20268
   745
fun refute_tac (ss : simpset) (i : int, justs : injust list) : tactic =
nipkow@6074
   746
  fn state =>
webertj@20268
   747
    let val _ = trace_thm ("refute_tac (on subgoal " ^ Int.toString i ^ ", with " ^
webertj@20268
   748
                             Int.toString (length justs) ^ " justification(s)):") state
webertj@20217
   749
        val sg          = theory_of_thm state
webertj@20217
   750
        val {neqE, ...} = Data.get sg
webertj@20217
   751
        fun just1 j =
webertj@20268
   752
          (* eliminate inequalities *)
webertj@20268
   753
          REPEAT_DETERM (eresolve_tac neqE i) THEN
webertj@20276
   754
            PRIMITIVE (trace_thm "State after neqE:") THEN
webertj@20268
   755
            (* use theorems generated from the actual justifications *)
webertj@20268
   756
            METAHYPS (fn asms => rtac (mkthm (sg, ss) asms j) 1) i
webertj@20268
   757
    in (* rewrite "[| A1; ...; An |] ==> B" to "[| A1; ...; An; ~B |] ==> False" *)
webertj@20268
   758
       DETERM (resolve_tac [LA_Logic.notI, LA_Logic.ccontr] i) THEN
webertj@20268
   759
       (* user-defined preprocessing of the subgoal *)
webertj@20268
   760
       DETERM (LA_Data.pre_tac i) THEN
webertj@20217
   761
       PRIMITIVE (trace_thm "State after pre_tac:") THEN
webertj@20268
   762
       (* prove every resulting subgoal, using its justification *)
webertj@20268
   763
       EVERY (map just1 justs)
webertj@20217
   764
    end  state;
nipkow@6074
   765
nipkow@5982
   766
(*
nipkow@5982
   767
Fast but very incomplete decider. Only premises and conclusions
nipkow@5982
   768
that are already (negated) (in)equations are taken into account.
nipkow@5982
   769
*)
webertj@20268
   770
fun simpset_lin_arith_tac (ss : simpset) (show_ex : bool) (i : int) (st : thm) =
webertj@20268
   771
  SUBGOAL (fn (A,_) =>
webertj@20217
   772
  let val params = rev (Logic.strip_params A)
webertj@20217
   773
      val Hs     = Logic.strip_assums_hyp A
webertj@20217
   774
      val concl  = Logic.strip_assums_concl A
nipkow@12932
   775
  in trace_thm ("Trying to refute subgoal " ^ string_of_int i) st;
webertj@20254
   776
     case prove (Thm.sign_of_thm st) params show_ex Hs concl of
skalberg@15531
   777
       NONE => (trace_msg "Refutation failed."; no_tac)
webertj@20217
   778
     | SOME js => (trace_msg "Refutation succeeded."; refute_tac ss (i, js))
wenzelm@9420
   779
  end) i st;
nipkow@5982
   780
webertj@20268
   781
fun lin_arith_tac (show_ex : bool) (i : int) (st : thm) =
webertj@20276
   782
  simpset_lin_arith_tac
webertj@20276
   783
    (Simplifier.theory_context (Thm.theory_of_thm st) Simplifier.empty_ss)
webertj@20217
   784
    show_ex i st;
wenzelm@17613
   785
webertj@20268
   786
fun cut_lin_arith_tac (ss : simpset) (i : int) =
wenzelm@17613
   787
  cut_facts_tac (Simplifier.prems_of_ss ss) i THEN
wenzelm@17613
   788
  simpset_lin_arith_tac ss false i;
nipkow@5982
   789
nipkow@13186
   790
(** Forward proof from theorems **)
nipkow@13186
   791
webertj@20268
   792
fun prover (ctxt as (sg, ss)) thms (Tconcl : term) (js : injust list) (pos : bool) : thm option =
webertj@20254
   793
let
webertj@20217
   794
    (* There is no "forward version" of 'pre_tac'.  Therefore we combine the     *)
webertj@20217
   795
    (* available theorems into a single proof state and perform "backward proof" *)
webertj@20217
   796
    (* using 'refute_tac'.                                                       *)
webertj@20217
   797
    val Hs    = map prop_of thms
webertj@20217
   798
    val Prop  = fold (curry Logic.mk_implies) (rev Hs) Tconcl
webertj@20217
   799
    val cProp = cterm_of sg Prop
webertj@20217
   800
    val concl = Goal.init cProp
webertj@20217
   801
                  |> refute_tac ss (1, js)
webertj@20217
   802
                  |> Seq.hd
webertj@20217
   803
                  |> Goal.finish
webertj@20217
   804
                  |> fold (fn thA => fn thAB => implies_elim thAB thA) thms
webertj@20217
   805
in SOME (trace_thm "Proved by lin. arith. prover:"
webertj@20217
   806
          (LA_Logic.mk_Eq concl)) end
nipkow@13186
   807
(* in case concl contains ?-var, which makes assume fail: *)
skalberg@15531
   808
handle THM _ => NONE;
nipkow@13186
   809
nipkow@13186
   810
(* PRE: concl is not negated!
nipkow@13186
   811
   This assumption is OK because
nipkow@13186
   812
   1. lin_arith_prover tries both to prove and disprove concl and
nipkow@13186
   813
   2. lin_arith_prover is applied by the simplifier which
nipkow@13186
   814
      dives into terms and will thus try the non-negated concl anyway.
nipkow@13186
   815
*)
webertj@20217
   816
webertj@20268
   817
fun lin_arith_prover sg ss (concl : term) : thm option =
webertj@20217
   818
let val thms = List.concat (map LA_Logic.atomize (prems_of_ss ss));
webertj@20217
   819
    val Hs = map prop_of thms
nipkow@6102
   820
    val Tconcl = LA_Logic.mk_Trueprop concl
webertj@20217
   821
(*
webertj@20217
   822
    val _ = trace_msg "lin_arith_prover"
webertj@20217
   823
    val _ = map (trace_thm "thms:") thms
webertj@20217
   824
    val _ = trace_msg ("concl:" ^ Sign.string_of_term sg concl)
webertj@20217
   825
*)
webertj@20254
   826
in case prove sg [] false Hs Tconcl of (* concl provable? *)
wenzelm@17515
   827
     SOME js => prover (sg, ss) thms Tconcl js true
skalberg@15531
   828
   | NONE => let val nTconcl = LA_Logic.neg_prop Tconcl
webertj@20254
   829
          in case prove sg [] false Hs nTconcl of (* ~concl provable? *)
wenzelm@17515
   830
               SOME js => prover (sg, ss) thms nTconcl js false
skalberg@15531
   831
             | NONE => NONE
nipkow@6079
   832
          end
nipkow@5982
   833
end;
nipkow@6074
   834
nipkow@6074
   835
end;