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[Mikael Zayenz Lagerkvist]

On Thu, Oct 9, 2008 at 8:05 AM, Mikael Zayenz Lagerkvist
<zayenz at gmail.com> wrote:
> I tried it (code below), and it works just as you wanted.

Hi again,

Christian pointed out to me that I had a small problem in my posted
code - if the member-function called gave a failure, then things could
go bad. Thus I've modified the code (see below) so that the
member-function returns an ExecStatus that the MemberFunctionBranching
can return.

Cheers,
Mikael

<code>
/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Mikael Lagerkvist <lagerkvist at gecode.org>
 *
 *  Copyright:
 *     Mikael Lagerkvist, 2008
 *
 *  Last modified:
 *     $Date: 2008-10-09 07:48:15 +0200 (Wed, 09 Oct 2008) $ by
$Author: zayenz $
 *     $Revision: 7912 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
 *  Permission is hereby granted, free of charge, to any person obtaining
 *  a copy of this software and associated documentation files (the
 *  "Software"), to deal in the Software without restriction, including
 *  without limitation the rights to use, copy, modify, merge, publish,
 *  distribute, sublicense, and/or sell copies of the Software, and to
 *  permit persons to whom the Software is furnished to do so, subject to
 *  the following conditions:
 *
 *  The above copyright notice and this permission notice shall be
 *  included in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */

#include "examples/support.hh"
#include <gecode/minimodel.hh>

/** \brief Branching for calling a space member function.
 */
template <class Model>
class MemberFunctionBranch : Branching {
public:
  /// Type of the member-function to call
  typedef ExecStatus (Model::*MemberFunction)();
private:
  /// Member function to call
  MemberFunction mf;
  /// Call member function just once
  bool done;

  /// Minimal branching description storing no information
  struct Description : public BranchingDesc {
    /// Initialize description for branching \a b, number of alternatives \a a.
    Description(const Branching* b, unsigned int a) : BranchingDesc(b,a) {}
    /// Report size occupied
    virtual size_t size(void) const { return sizeof(Description); }
  };

  /// Construct branching
  MemberFunctionBranch(Space* home, MemberFunction mf0)
    : Branching(home), mf(mf0), done(false) {}
  /// Copy constructor
  MemberFunctionBranch(Space* home, bool share,
                       MemberFunctionBranch<Model>& b)
    : Branching(home, share, b), mf(b.mf), done(b.done) {}

public:
  /// Check status of branching, return true if alternatives left.
  virtual bool status(const Space*) const {
    return !done;
  }
  /// Return branching description
  virtual BranchingDesc* description(const Space*) const {
    assert(!done);
    return new Description(this, 1);
  }
  /// Perform commit
  virtual ExecStatus commit(Space* home, const BranchingDesc*, unsigned int) {
    done = true;
    Model* model = static_cast<Model*>(home);
    return (model->*mf)();
  }
  /// Copy branching
  virtual Actor* copy(Space* home, bool share) {
    return new (home) MemberFunctionBranch(home, share, *this);
  }
  /// Reflection name
  virtual const char* name(void) const {
    return "MemberFunctionBranch";
  }
  /// Post branching
  static void post(Space* home, MemberFunction mf) {
    (void) new (home) MemberFunctionBranch<Model>(home,mf);
  }
};


/**
 * \brief %Example: n-%Queens puzzle with member function branchings
 *
 * \ingroup ExProblem
 */
class QueensMF : public Example {
protected:
  /// Position of queens on boards
  IntVarArray q;
public:
  ExecStatus addbranch(void) {
    branch(this, q, INT_VAR_SIZE_MIN, INT_VAL_MIN);
    MemberFunctionBranch<QueensMF>::post(this, &QueensMF::addprop);
    return failed() ? ES_FAILED : ES_OK;
  }
  ExecStatus addprop(void) {
    const int n = q.size();
    for (int i = 0; i<n; i++)
      for (int j = i+1; j<n; j++) {
        post(this, q[i] != q[j]);
        post(this, q[i]+i != q[j]+j);
        post(this, q[i]-i != q[j]-j);
      }
    return failed() ? ES_FAILED : ES_OK;
  }
  /// The actual problem
  QueensMF(const SizeOptions& opt)
    : q(this,opt.size(),0,opt.size()-1) {
    MemberFunctionBranch<QueensMF>::post(this, &QueensMF::addbranch);
  }

  /// Constructor for cloning \a s
  QueensMF(bool share, QueensMF& s) : Example(share,s) {
    q.update(this, share, s.q);
  }

  /// Perform copying during cloning
  virtual Space*
  copy(bool share) {
    return new QueensMF(share,*this);
  }

  /// Print solution
  virtual void
  print(std::ostream& os) {
    os << "\t";
    for (int i = 0; i < q.size(); i++) {
      os << q[i] << ", ";
      if ((i+1) % 10 == 0)
        os << std::endl << "\t";
    }
    os << std::endl;
  }

  /// Make variables available for visualisation
  virtual void
  getVars(Gecode::Reflection::VarMap& vm, bool registerOnly) {
    vm.putArray(this,q,"q", registerOnly);
  }
};

/** \brief Main-function
 *  \relates QueensMF
 */
int
main(int argc, char* argv[]) {
  SizeOptions opt("QueensMF");
  opt.iterations(500);
  opt.size(6);
  opt.parse(argc,argv);
  Example::run<QueensMF,DFS,SizeOptions>(opt);
  return 0;
}

// STATISTICS: example-any
</code>

-- 
Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/