/* Copyright (c) 1997-2010
   Ewgenij Gawrilow, Michael Joswig (Technische Universitaet Darmstadt, Germany)
   http://www.polymake.de

   This program is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 2, or (at your option) any
   later version: http://www.gnu.org/licenses/gpl.txt.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
--------------------------------------------------------------------------------
   $Project: polymake $$Id: bases_from_points.cc 10003 2010-12-24 02:09:22Z gawrilow $
*/

#include "polymake/client.h"
#include "polymake/Matrix.h"
#include "polymake/Rational.h"
#include "polymake/PowerSet.h"
#include "polymake/linalg.h"
#include "polymake/list"

namespace polymake { namespace matroid {

void bases_from_points(perl::Object m)
{
   const Matrix<Rational> points=m.give("POINTS");
   const int n_elements=points.rows();
   const int r=rank(points);
  
   std::list< Set<int> > bases;
   int n_bases=0;
  
   //test for each subset of size r
   for (Entire< Subsets_of_k<const sequence&> >::const_iterator i=entire(all_subsets_of_k(sequence(0,n_elements),r)); !i.at_end(); ++i) {
      const Matrix<Rational> b=points.minor(*i,All);
    
      if (rank(b)==r) {
	 bases.push_back(*i);
	 ++n_bases;
      }
   }
  
   m.take("BASES") << bases;
   m.take("N_BASES") << n_bases;
   m.take("RANK") << r;
   m.take("N_ELEMENTS") << n_elements;
}

Function4perl(&bases_from_points, "bases_from_points(Matroid)");

} }

// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
