diff -r 6ec5dbed8f18 -r b55e501a90ee lemon/concepts/path.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lemon/concepts/path.h	Thu Jan 24 11:31:19 2008 +0000
@@ -0,0 +1,307 @@
+/* -*- C++ -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2003-2008
+ * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+///\ingroup concept
+///\file
+///\brief Classes for representing paths in digraphs.
+///
+///\todo Iterators have obsolete style
+
+#ifndef LEMON_CONCEPT_PATH_H
+#define LEMON_CONCEPT_PATH_H
+
+#include <lemon/bits/invalid.h>
+#include <lemon/bits/utility.h>
+#include <lemon/concept_check.h>
+
+namespace lemon {
+  namespace concepts {
+
+    /// \addtogroup concept
+    /// @{
+
+    /// \brief A skeleton structure for representing directed paths in
+    /// a digraph.
+    ///
+    /// A skeleton structure for representing directed paths in a
+    /// digraph.  
+    /// \param _Digraph The digraph type in which the path is.
+    ///
+    /// In a sense, the path can be treated as a list of arcs. The
+    /// lemon path type stores just this list. As a consequence it
+    /// cannot enumerate the nodes in the path and the zero length
+    /// paths cannot store the source.
+    ///
+    template <typename _Digraph>
+    class Path {
+    public:
+
+      /// Type of the underlying digraph.
+      typedef _Digraph Digraph;
+      /// Arc type of the underlying digraph.
+      typedef typename Digraph::Arc Arc;
+
+      class ArcIt;
+
+      /// \brief Default constructor
+      Path() {}
+
+      /// \brief Template constructor
+      template <typename CPath>
+      Path(const CPath& cpath) {}
+
+      /// \brief Template assigment
+      template <typename CPath>
+      Path& operator=(const CPath& cpath) {}
+
+      /// Length of the path ie. the number of arcs in the path.
+      int length() const { return 0;}
+
+      /// Returns whether the path is empty.
+      bool empty() const { return true;}
+
+      /// Resets the path to an empty path.
+      void clear() {}
+
+      /// \brief Lemon style iterator for path arcs
+      ///
+      /// This class is used to iterate on the arcs of the paths.
+      class ArcIt {
+      public:
+	/// Default constructor
+	ArcIt() {}
+	/// Invalid constructor
+	ArcIt(Invalid) {}
+	/// Constructor for first arc
+	ArcIt(const Path &) {}
+
+        /// Conversion to Arc
+	operator Arc() const { return INVALID; }
+
+	/// Next arc
+	ArcIt& operator++() {return *this;}
+
+	/// Comparison operator
+	bool operator==(const ArcIt&) const {return true;}
+	/// Comparison operator
+	bool operator!=(const ArcIt&) const {return true;}
+ 	/// Comparison operator
+ 	bool operator<(const ArcIt&) const {return false;}
+
+      };
+
+      template <typename _Path>
+      struct Constraints {
+        void constraints() {
+          Path<Digraph> pc;
+          _Path p, pp(pc);
+          int l = p.length();
+          int e = p.empty();
+          p.clear();
+
+          p = pc;
+
+          typename _Path::ArcIt id, ii(INVALID), i(p);
+
+          ++i;
+          typename Digraph::Arc ed = i;
+
+          e = (i == ii);
+          e = (i != ii);
+          e = (i < ii);
+
+          ignore_unused_variable_warning(l);
+          ignore_unused_variable_warning(pp);
+          ignore_unused_variable_warning(e);
+          ignore_unused_variable_warning(id);
+          ignore_unused_variable_warning(ii);
+          ignore_unused_variable_warning(ed);
+        }
+      };
+
+    };
+
+    namespace _path_bits {
+      
+      template <typename _Digraph, typename _Path, typename RevPathTag = void>
+      struct PathDumperConstraints {
+        void constraints() {
+          int l = p.length();
+          int e = p.empty();
+
+          typename _Path::ArcIt id, i(p);
+
+          ++i;
+          typename _Digraph::Arc ed = i;
+
+          e = (i == INVALID);
+          e = (i != INVALID);
+
+          ignore_unused_variable_warning(l);
+          ignore_unused_variable_warning(e);
+          ignore_unused_variable_warning(id);
+          ignore_unused_variable_warning(ed);
+        }
+        _Path& p;
+      };
+
+      template <typename _Digraph, typename _Path>
+      struct PathDumperConstraints<
+        _Digraph, _Path, 
+        typename enable_if<typename _Path::RevPathTag, void>::type
+      > {
+        void constraints() {
+          int l = p.length();
+          int e = p.empty();
+
+          typename _Path::RevArcIt id, i(p);
+
+          ++i;
+          typename _Digraph::Arc ed = i;
+
+          e = (i == INVALID);
+          e = (i != INVALID);
+
+          ignore_unused_variable_warning(l);
+          ignore_unused_variable_warning(e);
+          ignore_unused_variable_warning(id);
+          ignore_unused_variable_warning(ed);
+        }
+        _Path& p;
+      };
+    
+    }
+
+
+    /// \brief A skeleton structure for path dumpers.
+    ///
+    /// A skeleton structure for path dumpers. The path dumpers are
+    /// the generalization of the paths. The path dumpers can
+    /// enumerate the arcs of the path wheter in forward or in
+    /// backward order.  In most time these classes are not used
+    /// directly rather it used to assign a dumped class to a real
+    /// path type.
+    ///
+    /// The main purpose of this concept is that the shortest path
+    /// algorithms can enumerate easily the arcs in reverse order.
+    /// If we would like to give back a real path from these
+    /// algorithms then we should create a temporarly path object. In
+    /// Lemon such algorithms gives back a path dumper what can
+    /// assigned to a real path and the dumpers can be implemented as
+    /// an adaptor class to the predecessor map.
+
+    /// \param _Digraph  The digraph type in which the path is.
+    ///
+    /// The paths can be constructed from any path type by a
+    /// template constructor or a template assignment operator.
+    /// 
+    template <typename _Digraph>
+    class PathDumper {
+    public:
+
+      /// Type of the underlying digraph.
+      typedef _Digraph Digraph;
+      /// Arc type of the underlying digraph.
+      typedef typename Digraph::Arc Arc;
+
+      /// Length of the path ie. the number of arcs in the path.
+      int length() const { return 0;}
+
+      /// Returns whether the path is empty.
+      bool empty() const { return true;}
+
+      /// \brief Forward or reverse dumping
+      ///
+      /// If the RevPathTag is defined and true then reverse dumping
+      /// is provided in the path dumper. In this case instead of the
+      /// ArcIt the RevArcIt iterator should be implemented in the
+      /// dumper.
+      typedef False RevPathTag;
+
+      /// \brief Lemon style iterator for path arcs
+      ///
+      /// This class is used to iterate on the arcs of the paths.
+      class ArcIt {
+      public:
+	/// Default constructor
+	ArcIt() {}
+	/// Invalid constructor
+	ArcIt(Invalid) {}
+	/// Constructor for first arc
+	ArcIt(const PathDumper&) {}
+
+        /// Conversion to Arc
+	operator Arc() const { return INVALID; }
+
+	/// Next arc
+	ArcIt& operator++() {return *this;}
+
+	/// Comparison operator
+	bool operator==(const ArcIt&) const {return true;}
+	/// Comparison operator
+	bool operator!=(const ArcIt&) const {return true;}
+ 	/// Comparison operator
+ 	bool operator<(const ArcIt&) const {return false;}
+
+      };
+
+      /// \brief Lemon style iterator for path arcs
+      ///
+      /// This class is used to iterate on the arcs of the paths in
+      /// reverse direction.
+      class RevArcIt {
+      public:
+	/// Default constructor
+	RevArcIt() {}
+	/// Invalid constructor
+	RevArcIt(Invalid) {}
+	/// Constructor for first arc
+	RevArcIt(const PathDumper &) {}
+
+        /// Conversion to Arc
+	operator Arc() const { return INVALID; }
+
+	/// Next arc
+	RevArcIt& operator++() {return *this;}
+
+	/// Comparison operator
+	bool operator==(const RevArcIt&) const {return true;}
+	/// Comparison operator
+	bool operator!=(const RevArcIt&) const {return true;}
+ 	/// Comparison operator
+ 	bool operator<(const RevArcIt&) const {return false;}
+
+      };
+
+      template <typename _Path>
+      struct Constraints {
+        void constraints() {
+          function_requires<_path_bits::
+            PathDumperConstraints<Digraph, _Path> >();
+        }
+      };
+
+    };
+
+
+    ///@}
+  }
+
+} // namespace lemon
+
+#endif // LEMON_CONCEPT_PATH_H