we still require this file for 3d

Algebraic_kernel_d/include/CGAL/Algebraic_curve_kernel_2/Bitstream_descartes_at_x/Best_approximation_cache.h

@@ -0,0 +1,122 @@
+// TODO: Add licence
+//
+// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
+// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+//
+// $URL:$
+// $Id$
+// 
+//
+// Author(s)     : Michael Kerber <mkerber@mpi-inf.mpg.de>
+//
+// ============================================================================
+
+#ifndef CGAL_BEST_APPROXIMATION_CACHE
+#define CGAL_BEST_APPROXIMATION_CACHE 1
+
+
+#include <CGAL/basic.h>
+#include <CGAL/Handle_with_policy.h>
+#include <map>
+#include <vector>
+
+CGAL_BEGIN_NAMESPACE
+
+
+  namespace CGALi {
+
+    /*!
+     * \brief Stores computed approximations for coefficients.
+     *
+     * During the execution of the Bitstream Descartes method, approximations
+     * of the coefficients are computed independently by different branches of
+     * the Descartes tree. To avoid computing them several times, the best
+     * konwn approximation for a special coefficient is stored in a \c std::map
+     * structure. The data contains the used precision and the integer that
+     * represents the coefficient for this precision, according to the 
+     * \c CGAL::CGALi::Bitstream_descartes_rndl_tree_traits definition.
+     */
+    template<typename Coefficient_,typename Integer_>
+      class Best_approximation_cache 
+      : public ::CGAL::Handle_with_policy<std::map<Coefficient_,std::pair<long,Integer_> > > {
+
+      public:
+
+      //! The Coefficient type
+      typedef Coefficient_ Coefficient;
+
+      //! The integer type
+      typedef Integer_ Integer;
+
+      typedef std::pair<long,Integer> Data_pair;
+
+      typedef std::map<Coefficient,Data_pair> Map;
+
+      typedef ::CGAL::Handle_with_policy<Map> Base;
+
+      typedef Best_approximation_cache<Coefficient,Integer> Self;
+
+      //! Default constructor
+      Best_approximation_cache() {
+      }
+      
+      //! Copy constructor
+      Best_approximation_cache(const Self& s)
+	: Base(static_cast<const Base&>(s))
+	{}
+      
+      /*! 
+       * \brief Checks whether the coefficient \c c already has already been
+       * approximated.
+       */
+      bool approximation_exists(Coefficient c) const {
+	typename Map::const_iterator it = this->ptr()->find(c);
+	return it!=this->ptr()->end();
+      }
+
+      /*!
+       * \brief The best approximation known for the coefficient <tt>c</tt>
+       * is returned.
+       *
+       * It is necessary to check whether an approximation of <tt>c</tt> exists
+       * using the \c approximation_exists method beforehand!
+       */
+      void get_best_approximation(Coefficient c,long& prec, Integer& val) const{
+	typename Map::const_iterator it = this->ptr()->find(c);
+	CGAL_assertion(it!=this->ptr()->end());
+	prec = it->second.first;
+	val = it->second.second;
+      }
+
+      /*!
+       * \brief Updates the approximation memory
+       *
+       * If an approximation for <tt>c</tt> is known, this method can be used
+       * to store it for later usage. The update is only performed if the
+       * precision is indeed higher than the current precision in the map.
+       */
+      void update_approximation(Coefficient c,long prec, const Integer& val) {
+	typename Map::iterator it = this->ptr()->find(c);
+	if(it!=this->ptr()->end()) {
+	  if(it->second.first >= prec) {
+	    return;
+	  }
+	  else {
+	    Data_pair better_pair = std::make_pair(prec,val);
+	    it->second=better_pair;
+	  }
+	}
+	else {
+	  Data_pair new_pair = std::make_pair(prec,val);
+	  this->ptr()->operator[](c)=new_pair;
+	}
+	
+      }
+    };
+    
+
+  }// namespace CGALi
+
+CGAL_END_NAMESPACE
+
+#endif // AcX_BEST_APPROXIMATION_CACHE