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/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2003
 *
 *  Last modified:
 *     $Date: 2006-08-04 16:03:26 +0200 (Fri, 04 Aug 2006) $ by $Author: schulte $
 *     $Revision: 3512 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
 *  See the file "LICENSE" for information on usage and
 *  redistribution of this file, and for a
 *     DISCLAIMER OF ALL WARRANTIES.
 *
 */

namespace Gecode { namespace Int { namespace Rel {

  template <class View>
  inline
  Lex<View>::Lex(Space* home,
                 ViewArray<ViewTuple<View,2> >& xy, bool s)
    : NaryPropagator<ViewTuple<View,2>,PC_INT_BND>(home,xy), strict(s) {}

  template <class View>
  forceinline
  Lex<View>::Lex(Space* home, bool share, Lex<View>& p)
    : NaryPropagator<ViewTuple<View,2>,PC_INT_BND>(home,share,p),
      strict(p.strict) {}

  template <class View>
  Actor*
  Lex<View>::copy(Space* home, bool share) {
    return new (home) Lex<View>(home,share,*this);
  }

  template <class View>
  ExecStatus
  Lex<View>::propagate(Space* home) {
    /*
     * State 1
     *
     */
    {
      int i = 0;
      int n = x.size();

      while ((i < n) && (x[i][0].min() == x[i][1].max())) {
        // case: =, >=
        GECODE_ME_CHECK(x[i][0].lq(home,x[i][1].max()));
        GECODE_ME_CHECK(x[i][1].gq(home,x[i][0].min()));
        i++;
      }

      if (i == n) // case: $
        return strict ? ES_FAILED : ES_SUBSUMED;

      // Possible cases left: <, <=, > (yields failure), ?
      GECODE_ME_CHECK(x[i][0].lq(home,x[i][1].max()));
      GECODE_ME_CHECK(x[i][1].gq(home,x[i][0].min()));

      if (x[i][0].max() < x[i][1].min()) // case: < (after tell)
        return ES_SUBSUMED;

      // x[i][0] can never be equal to x[i][1] (otherwise: >=)
      assert(!(x[i][0].assigned() && x[i][1].assigned() &&
               x[i][0].val() == x[i][1].val()));
      // Remove all elements between 0...i-1 as they are assigned and equal
      x.drop_fst(i);
      // After this, execution continues at [1]
    }

    /*
     * State 2
     *   prefix: (?|<=)
     *
     */
    {
      int i = 1;
      int n = x.size();

      while ((i < n) &&
             (x[i][0].min() == x[i][1].max()) &&
             (x[i][0].max() == x[i][1].min())) { // case: =
        assert(x[i][0].assigned() && x[i][1].assigned() &&
               (x[i][0].val() == x[i][1].val()));
        i++;
      }

      if (i == n) { // case: $
        if (strict)
          goto rewrite_le;
        else
          goto rewrite_lq;
      }

      if (x[i][0].max() < x[i][1].min()) // case: <
        goto rewrite_lq;

      if (x[i][0].min() > x[i][1].max()) // case: >
        goto rewrite_le;

      if (i > 1) {
        // Remove equal elements [1...i-1], keep element [0]
        x[i-1]=x[0]; x.drop_fst(i-1);
      }
    }

    if (x[1][0].max() <= x[1][1].min()) {
      // case: <= (invariant: not =, <)
      /*
       * State 3
       *   prefix: (?|<=),<=
       *
       */
      int i = 2;
      int n = x.size();

      while ((i < n) && (x[i][0].max() == x[i][1].min())) // case: <=, =
        i++;

      if (i == n) { // case: $
        if (strict)
          return ES_FIX;
        else
          goto rewrite_lq;
      }

      if (x[i][0].max() < x[i][1].min()) // case: <
        goto rewrite_lq;

      if (x[i][0].min() > x[i][1].max()) { // case: >
        // Eliminate [i]...[n-1]
        for (int j=i; j<n; j++)
          x[j].cancel(home,this,PC_INT_BND);
        x.size(i);
        strict = true;
      }

      return ES_FIX;
    }

    if (x[1][0].min() >= x[1][1].max()) {
      // case: >= (invariant: not =, >)
      /*
       * State 4
       *   prefix: (?|<=) >=
       *
       */
      int i = 2;
      int n = x.size();

      while ((i < n) && (x[i][0].min() == x[i][1].max()))
        // case: >=, =
        i++;

      if (i == n) { // case: $
        if (strict)
          goto rewrite_le;
        else
          return ES_FIX;
      }

      if (x[i][0].min() > x[i][1].max()) // case: >
        goto rewrite_le;

      if (x[i][0].max() < x[i][1].min()) { // case: <
        // Eliminate [i]...[n-1]
        for (int j=i; j<n; j++)
          x[j].cancel(home,this,PC_INT_BND);
        x.size(i);
        strict = false;
      }

      return ES_FIX;
    }

    return ES_FIX;

  rewrite_le:
    GECODE_ES_CHECK(Le<View>::post(home,x[0][0],x[0][1]));
    return ES_SUBSUMED;

  rewrite_lq:
    GECODE_ES_CHECK(Lq<View>::post(home,x[0][0],x[0][1]));
    return ES_SUBSUMED;
  }

  template <class View>
  ExecStatus
  Lex<View>::post(Space* home,
                  ViewArray<ViewTuple<View,2> >& xy, bool strict){
    if (xy.size() == 0)
      return strict ? ES_FAILED : ES_OK;
    if (xy.size() == 1)
      if (strict)
        return Le<View>::post(home,xy[0][0],xy[0][1]);
      else
        return Lq<View>::post(home,xy[0][0],xy[0][1]);
    (void) new (home) Lex<View>(home,xy,strict);
    return ES_OK;
  }

}}}

// STATISTICS: int-prop