diff --git a/lemon/bits/variant.h b/lemon/bits/variant.h
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+/* -*- mode: C++; indent-tabs-mode: nil; -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library.
+ *
+ * Copyright (C) 2003-2009
+ * 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.
+ *
+ */
+
+#ifndef LEMON_BITS_VARIANT_H
+#define LEMON_BITS_VARIANT_H
+
+#include <lemon/assert.h>
+
+// \file
+// \brief Variant types
+
+namespace lemon {
+
+  namespace _variant_bits {
+
+    template <int left, int right>
+    struct CTMax {
+      static const int value = left < right ? right : left;
+    };
+
+  }
+
+
+  // \brief Simple Variant type for two types
+  //
+  // Simple Variant type for two types. The Variant type is a type-safe
+  // union. C++ has strong limitations for using unions, for
+  // example you cannot store a type with non-default constructor or
+  // destructor in a union. This class always knowns the current
+  // state of the variant and it cares for the proper construction
+  // and destruction.
+  template <typename _First, typename _Second>
+  class BiVariant {
+  public:
+
+    // \brief The \c First type.
+    typedef _First First;
+    // \brief The \c Second type.
+    typedef _Second Second;
+
+    // \brief Constructor
+    //
+    // This constructor initalizes to the default value of the \c First
+    // type.
+    BiVariant() {
+      flag = true;
+      new(reinterpret_cast<First*>(data)) First();
+    }
+
+    // \brief Constructor
+    //
+    // This constructor initalizes to the given value of the \c First
+    // type.
+    BiVariant(const First& f) {
+      flag = true;
+      new(reinterpret_cast<First*>(data)) First(f);
+    }
+
+    // \brief Constructor
+    //
+    // This constructor initalizes to the given value of the \c
+    // Second type.
+    BiVariant(const Second& s) {
+      flag = false;
+      new(reinterpret_cast<Second*>(data)) Second(s);
+    }
+
+    // \brief Copy constructor
+    //
+    // Copy constructor
+    BiVariant(const BiVariant& bivariant) {
+      flag = bivariant.flag;
+      if (flag) {
+        new(reinterpret_cast<First*>(data)) First(bivariant.first());
+      } else {
+        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
+      }
+    }
+
+    // \brief Destrcutor
+    //
+    // Destructor
+    ~BiVariant() {
+      destroy();
+    }
+
+    // \brief Set to the default value of the \c First type.
+    //
+    // This function sets the variant to the default value of the \c
+    // First type.
+    BiVariant& setFirst() {
+      destroy();
+      flag = true;
+      new(reinterpret_cast<First*>(data)) First();
+      return *this;
+    }
+
+    // \brief Set to the given value of the \c First type.
+    //
+    // This function sets the variant to the given value of the \c
+    // First type.
+    BiVariant& setFirst(const First& f) {
+      destroy();
+      flag = true;
+      new(reinterpret_cast<First*>(data)) First(f);
+      return *this;
+    }
+
+    // \brief Set to the default value of the \c Second type.
+    //
+    // This function sets the variant to the default value of the \c
+    // Second type.
+    BiVariant& setSecond() {
+      destroy();
+      flag = false;
+      new(reinterpret_cast<Second*>(data)) Second();
+      return *this;
+    }
+
+    // \brief Set to the given value of the \c Second type.
+    //
+    // This function sets the variant to the given value of the \c
+    // Second type.
+    BiVariant& setSecond(const Second& s) {
+      destroy();
+      flag = false;
+      new(reinterpret_cast<Second*>(data)) Second(s);
+      return *this;
+    }
+
+    // \brief Operator form of the \c setFirst()
+    BiVariant& operator=(const First& f) {
+      return setFirst(f);
+    }
+
+    // \brief Operator form of the \c setSecond()
+    BiVariant& operator=(const Second& s) {
+      return setSecond(s);
+    }
+
+    // \brief Assign operator
+    BiVariant& operator=(const BiVariant& bivariant) {
+      if (this == &bivariant) return *this;
+      destroy();
+      flag = bivariant.flag;
+      if (flag) {
+        new(reinterpret_cast<First*>(data)) First(bivariant.first());
+      } else {
+        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
+      }
+      return *this;
+    }
+
+    // \brief Reference to the value
+    //
+    // Reference to the value of the \c First type.
+    // \pre The BiVariant should store value of \c First type.
+    First& first() {
+      LEMON_DEBUG(flag, "Variant wrong state");
+      return *reinterpret_cast<First*>(data);
+    }
+
+    // \brief Const reference to the value
+    //
+    // Const reference to the value of the \c First type.
+    // \pre The BiVariant should store value of \c First type.
+    const First& first() const {
+      LEMON_DEBUG(flag, "Variant wrong state");
+      return *reinterpret_cast<const First*>(data);
+    }
+
+    // \brief Operator form of the \c first()
+    operator First&() { return first(); }
+    // \brief Operator form of the const \c first()
+    operator const First&() const { return first(); }
+
+    // \brief Reference to the value
+    //
+    // Reference to the value of the \c Second type.
+    // \pre The BiVariant should store value of \c Second type.
+    Second& second() {
+      LEMON_DEBUG(!flag, "Variant wrong state");
+      return *reinterpret_cast<Second*>(data);
+    }
+
+    // \brief Const reference to the value
+    //
+    // Const reference to the value of the \c Second type.
+    // \pre The BiVariant should store value of \c Second type.
+    const Second& second() const {
+      LEMON_DEBUG(!flag, "Variant wrong state");
+      return *reinterpret_cast<const Second*>(data);
+    }
+
+    // \brief Operator form of the \c second()
+    operator Second&() { return second(); }
+    // \brief Operator form of the const \c second()
+    operator const Second&() const { return second(); }
+
+    // \brief %True when the variant is in the first state
+    //
+    // %True when the variant stores value of the \c First type.
+    bool firstState() const { return flag; }
+
+    // \brief %True when the variant is in the second state
+    //
+    // %True when the variant stores value of the \c Second type.
+    bool secondState() const { return !flag; }
+
+  private:
+
+    void destroy() {
+      if (flag) {
+        reinterpret_cast<First*>(data)->~First();
+      } else {
+        reinterpret_cast<Second*>(data)->~Second();
+      }
+    }
+
+    char data[_variant_bits::CTMax<sizeof(First), sizeof(Second)>::value];
+    bool flag;
+  };
+
+  namespace _variant_bits {
+
+    template <int _idx, typename _TypeMap>
+    struct Memory {
+
+      typedef typename _TypeMap::template Map<_idx>::Type Current;
+
+      static void destroy(int index, char* place) {
+        if (index == _idx) {
+          reinterpret_cast<Current*>(place)->~Current();
+        } else {
+          Memory<_idx - 1, _TypeMap>::destroy(index, place);
+        }
+      }
+
+      static void copy(int index, char* to, const char* from) {
+        if (index == _idx) {
+          new (reinterpret_cast<Current*>(to))
+            Current(reinterpret_cast<const Current*>(from));
+        } else {
+          Memory<_idx - 1, _TypeMap>::copy(index, to, from);
+        }
+      }
+
+    };
+
+    template <typename _TypeMap>
+    struct Memory<-1, _TypeMap> {
+
+      static void destroy(int, char*) {
+        LEMON_DEBUG(false, "Variant wrong index.");
+      }
+
+      static void copy(int, char*, const char*) {
+        LEMON_DEBUG(false, "Variant wrong index.");
+      }
+    };
+
+    template <int _idx, typename _TypeMap>
+    struct Size {
+      static const int value =
+      CTMax<sizeof(typename _TypeMap::template Map<_idx>::Type),
+            Size<_idx - 1, _TypeMap>::value>::value;
+    };
+
+    template <typename _TypeMap>
+    struct Size<0, _TypeMap> {
+      static const int value =
+      sizeof(typename _TypeMap::template Map<0>::Type);
+    };
+
+  }
+
+  // \brief Variant type
+  //
+  // Simple Variant type. The Variant type is a type-safe union.
+  // C++ has strong limitations for using unions, for example you
+  // cannot store type with non-default constructor or destructor in
+  // a union. This class always knowns the current state of the
+  // variant and it cares for the proper construction and
+  // destruction.
+  //
+  // \param _num The number of the types which can be stored in the
+  // variant type.
+  // \param _TypeMap This class describes the types of the Variant. The
+  // _TypeMap::Map<index>::Type should be a valid type for each index
+  // in the range {0, 1, ..., _num - 1}. The \c VariantTypeMap is helper
+  // class to define such type mappings up to 10 types.
+  //
+  // And the usage of the class:
+  //\code
+  // typedef Variant<3, VariantTypeMap<int, std::string, double> > MyVariant;
+  // MyVariant var;
+  // var.set<0>(12);
+  // std::cout << var.get<0>() << std::endl;
+  // var.set<1>("alpha");
+  // std::cout << var.get<1>() << std::endl;
+  // var.set<2>(0.75);
+  // std::cout << var.get<2>() << std::endl;
+  //\endcode
+  //
+  // The result of course:
+  //\code
+  // 12
+  // alpha
+  // 0.75
+  //\endcode
+  template <int _num, typename _TypeMap>
+  class Variant {
+  public:
+
+    static const int num = _num;
+
+    typedef _TypeMap TypeMap;
+
+    // \brief Constructor
+    //
+    // This constructor initalizes to the default value of the \c type
+    // with 0 index.
+    Variant() {
+      flag = 0;
+      new(reinterpret_cast<typename TypeMap::template Map<0>::Type*>(data))
+        typename TypeMap::template Map<0>::Type();
+    }
+
+
+    // \brief Copy constructor
+    //
+    // Copy constructor
+    Variant(const Variant& variant) {
+      flag = variant.flag;
+      _variant_bits::Memory<num - 1, TypeMap>::copy(flag, data, variant.data);
+    }
+
+    // \brief Assign operator
+    //
+    // Assign operator
+    Variant& operator=(const Variant& variant) {
+      if (this == &variant) return *this;
+      _variant_bits::Memory<num - 1, TypeMap>::
+        destroy(flag, data);
+      flag = variant.flag;
+      _variant_bits::Memory<num - 1, TypeMap>::
+        copy(flag, data, variant.data);
+      return *this;
+    }
+
+    // \brief Destrcutor
+    //
+    // Destructor
+    ~Variant() {
+      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
+    }
+
+    // \brief Set to the default value of the type with \c _idx index.
+    //
+    // This function sets the variant to the default value of the
+    // type with \c _idx index.
+    template <int _idx>
+    Variant& set() {
+      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
+      flag = _idx;
+      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
+        typename TypeMap::template Map<_idx>::Type();
+      return *this;
+    }
+
+    // \brief Set to the given value of the type with \c _idx index.
+    //
+    // This function sets the variant to the given value of the type
+    // with \c _idx index.
+    template <int _idx>
+    Variant& set(const typename _TypeMap::template Map<_idx>::Type& init) {
+      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
+      flag = _idx;
+      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
+        typename TypeMap::template Map<_idx>::Type(init);
+      return *this;
+    }
+
+    // \brief Gets the current value of the type with \c _idx index.
+    //
+    // Gets the current value of the type with \c _idx index.
+    template <int _idx>
+    const typename TypeMap::template Map<_idx>::Type& get() const {
+      LEMON_DEBUG(_idx == flag, "Variant wrong index");
+      return *reinterpret_cast<const typename TypeMap::
+        template Map<_idx>::Type*>(data);
+    }
+
+    // \brief Gets the current value of the type with \c _idx index.
+    //
+    // Gets the current value of the type with \c _idx index.
+    template <int _idx>
+    typename _TypeMap::template Map<_idx>::Type& get() {
+      LEMON_DEBUG(_idx == flag, "Variant wrong index");
+      return *reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>
+        (data);
+    }
+
+    // \brief Returns the current state of the variant.
+    //
+    // Returns the current state of the variant.
+    int state() const {
+      return flag;
+    }
+
+  private:
+
+    char data[_variant_bits::Size<num - 1, TypeMap>::value];
+    int flag;
+  };
+
+  namespace _variant_bits {
+
+    template <int _index, typename _List>
+    struct Get {
+      typedef typename Get<_index - 1, typename _List::Next>::Type Type;
+    };
+
+    template <typename _List>
+    struct Get<0, _List> {
+      typedef typename _List::Type Type;
+    };
+
+    struct List {};
+
+    template <typename _Type, typename _List>
+    struct Insert {
+      typedef _List Next;
+      typedef _Type Type;
+    };
+
+    template <int _idx, typename _T0, typename _T1, typename _T2,
+              typename _T3, typename _T4, typename _T5, typename _T6,
+              typename _T7, typename _T8, typename _T9>
+    struct Mapper {
+      typedef List L10;
+      typedef Insert<_T9, L10> L9;
+      typedef Insert<_T8, L9> L8;
+      typedef Insert<_T7, L8> L7;
+      typedef Insert<_T6, L7> L6;
+      typedef Insert<_T5, L6> L5;
+      typedef Insert<_T4, L5> L4;
+      typedef Insert<_T3, L4> L3;
+      typedef Insert<_T2, L3> L2;
+      typedef Insert<_T1, L2> L1;
+      typedef Insert<_T0, L1> L0;
+      typedef typename Get<_idx, L0>::Type Type;
+    };
+
+  }
+
+  // \brief Helper class for Variant
+  //
+  // Helper class to define type mappings for Variant. This class
+  // converts the template parameters to be mappable by integer.
+  // \see Variant
+  template <
+    typename _T0,
+    typename _T1 = void, typename _T2 = void, typename _T3 = void,
+    typename _T4 = void, typename _T5 = void, typename _T6 = void,
+    typename _T7 = void, typename _T8 = void, typename _T9 = void>
+  struct VariantTypeMap {
+    template <int _idx>
+    struct Map {
+      typedef typename _variant_bits::
+      Mapper<_idx, _T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9>::Type
+      Type;
+    };
+  };
+
+}
+
+
+#endif