lemon/bits/variant.h
author Peter Kovacs <kpeter@inf.elte.hu>
Thu, 12 Nov 2009 23:17:34 +0100
changeset 805 d3e32a777d0b
parent 431 9dfaf6efc36f
permissions -rw-r--r--
Port CapacityScaling from SVN -r3524 (#180)
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/* -*- mode: C++; indent-tabs-mode: nil; -*-
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 *
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 * This file is a part of LEMON, a generic C++ optimization library.
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 *
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 * Copyright (C) 2003-2009
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 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_BITS_VARIANT_H
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#define LEMON_BITS_VARIANT_H
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#include <lemon/assert.h>
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// \file
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// \brief Variant types
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namespace lemon {
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  namespace _variant_bits {
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    template <int left, int right>
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    struct CTMax {
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      static const int value = left < right ? right : left;
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    };
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  }
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  // \brief Simple Variant type for two types
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  //
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  // Simple Variant type for two types. The Variant type is a type-safe
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  // union. C++ has strong limitations for using unions, for
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  // example you cannot store a type with non-default constructor or
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  // destructor in a union. This class always knowns the current
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  // state of the variant and it cares for the proper construction
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  // and destruction.
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  template <typename _First, typename _Second>
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  class BiVariant {
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  public:
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    // \brief The \c First type.
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    typedef _First First;
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    // \brief The \c Second type.
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    typedef _Second Second;
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    // \brief Constructor
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    //
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    // This constructor initalizes to the default value of the \c First
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    // type.
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    BiVariant() {
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      flag = true;
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      new(reinterpret_cast<First*>(data)) First();
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    }
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    // \brief Constructor
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    //
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    // This constructor initalizes to the given value of the \c First
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    // type.
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    BiVariant(const First& f) {
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      flag = true;
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      new(reinterpret_cast<First*>(data)) First(f);
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    }
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    // \brief Constructor
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    //
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    // This constructor initalizes to the given value of the \c
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    // Second type.
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    BiVariant(const Second& s) {
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      flag = false;
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      new(reinterpret_cast<Second*>(data)) Second(s);
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    }
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    // \brief Copy constructor
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    //
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    // Copy constructor
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    BiVariant(const BiVariant& bivariant) {
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      flag = bivariant.flag;
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      if (flag) {
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        new(reinterpret_cast<First*>(data)) First(bivariant.first());
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      } else {
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        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
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      }
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    }
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    // \brief Destrcutor
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    //
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    // Destructor
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    ~BiVariant() {
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      destroy();
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    }
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    // \brief Set to the default value of the \c First type.
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    //
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    // This function sets the variant to the default value of the \c
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    // First type.
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    BiVariant& setFirst() {
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      destroy();
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      flag = true;
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      new(reinterpret_cast<First*>(data)) First();
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      return *this;
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    }
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    // \brief Set to the given value of the \c First type.
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    //
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    // This function sets the variant to the given value of the \c
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    // First type.
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    BiVariant& setFirst(const First& f) {
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      destroy();
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      flag = true;
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      new(reinterpret_cast<First*>(data)) First(f);
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      return *this;
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    }
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    // \brief Set to the default value of the \c Second type.
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    //
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    // This function sets the variant to the default value of the \c
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    // Second type.
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    BiVariant& setSecond() {
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      destroy();
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      flag = false;
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      new(reinterpret_cast<Second*>(data)) Second();
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      return *this;
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    }
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    // \brief Set to the given value of the \c Second type.
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    //
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    // This function sets the variant to the given value of the \c
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    // Second type.
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    BiVariant& setSecond(const Second& s) {
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      destroy();
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      flag = false;
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      new(reinterpret_cast<Second*>(data)) Second(s);
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      return *this;
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    }
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    // \brief Operator form of the \c setFirst()
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    BiVariant& operator=(const First& f) {
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      return setFirst(f);
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    }
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    // \brief Operator form of the \c setSecond()
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    BiVariant& operator=(const Second& s) {
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      return setSecond(s);
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    }
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    // \brief Assign operator
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    BiVariant& operator=(const BiVariant& bivariant) {
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      if (this == &bivariant) return *this;
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      destroy();
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      flag = bivariant.flag;
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      if (flag) {
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        new(reinterpret_cast<First*>(data)) First(bivariant.first());
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      } else {
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        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
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      }
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      return *this;
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    }
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    // \brief Reference to the value
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    //
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    // Reference to the value of the \c First type.
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    // \pre The BiVariant should store value of \c First type.
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    First& first() {
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      LEMON_DEBUG(flag, "Variant wrong state");
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      return *reinterpret_cast<First*>(data);
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    }
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    // \brief Const reference to the value
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    //
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    // Const reference to the value of the \c First type.
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    // \pre The BiVariant should store value of \c First type.
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    const First& first() const {
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      LEMON_DEBUG(flag, "Variant wrong state");
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      return *reinterpret_cast<const First*>(data);
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    }
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    // \brief Operator form of the \c first()
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    operator First&() { return first(); }
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    // \brief Operator form of the const \c first()
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    operator const First&() const { return first(); }
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    // \brief Reference to the value
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    //
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    // Reference to the value of the \c Second type.
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    // \pre The BiVariant should store value of \c Second type.
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    Second& second() {
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      LEMON_DEBUG(!flag, "Variant wrong state");
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      return *reinterpret_cast<Second*>(data);
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    }
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    // \brief Const reference to the value
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    //
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    // Const reference to the value of the \c Second type.
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    // \pre The BiVariant should store value of \c Second type.
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    const Second& second() const {
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      LEMON_DEBUG(!flag, "Variant wrong state");
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      return *reinterpret_cast<const Second*>(data);
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    }
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    // \brief Operator form of the \c second()
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    operator Second&() { return second(); }
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    // \brief Operator form of the const \c second()
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    operator const Second&() const { return second(); }
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    // \brief %True when the variant is in the first state
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    //
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    // %True when the variant stores value of the \c First type.
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    bool firstState() const { return flag; }
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    // \brief %True when the variant is in the second state
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    //
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    // %True when the variant stores value of the \c Second type.
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    bool secondState() const { return !flag; }
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  private:
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    void destroy() {
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      if (flag) {
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        reinterpret_cast<First*>(data)->~First();
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      } else {
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        reinterpret_cast<Second*>(data)->~Second();
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      }
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    }
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    char data[_variant_bits::CTMax<sizeof(First), sizeof(Second)>::value];
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    bool flag;
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  };
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  namespace _variant_bits {
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    template <int _idx, typename _TypeMap>
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    struct Memory {
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      typedef typename _TypeMap::template Map<_idx>::Type Current;
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      static void destroy(int index, char* place) {
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        if (index == _idx) {
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          reinterpret_cast<Current*>(place)->~Current();
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        } else {
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          Memory<_idx - 1, _TypeMap>::destroy(index, place);
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        }
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      }
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      static void copy(int index, char* to, const char* from) {
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        if (index == _idx) {
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          new (reinterpret_cast<Current*>(to))
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            Current(reinterpret_cast<const Current*>(from));
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        } else {
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          Memory<_idx - 1, _TypeMap>::copy(index, to, from);
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        }
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      }
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    };
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    template <typename _TypeMap>
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    struct Memory<-1, _TypeMap> {
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      static void destroy(int, char*) {
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        LEMON_DEBUG(false, "Variant wrong index.");
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      }
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      static void copy(int, char*, const char*) {
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        LEMON_DEBUG(false, "Variant wrong index.");
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      }
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    };
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    template <int _idx, typename _TypeMap>
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    struct Size {
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      static const int value =
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      CTMax<sizeof(typename _TypeMap::template Map<_idx>::Type),
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            Size<_idx - 1, _TypeMap>::value>::value;
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    };
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    template <typename _TypeMap>
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    struct Size<0, _TypeMap> {
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      static const int value =
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      sizeof(typename _TypeMap::template Map<0>::Type);
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    };
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  }
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  // \brief Variant type
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  //
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  // Simple Variant type. The Variant type is a type-safe union.
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  // C++ has strong limitations for using unions, for example you
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  // cannot store type with non-default constructor or destructor in
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  // a union. This class always knowns the current state of the
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  // variant and it cares for the proper construction and
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  // destruction.
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  //
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  // \param _num The number of the types which can be stored in the
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  // variant type.
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  // \param _TypeMap This class describes the types of the Variant. The
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  // _TypeMap::Map<index>::Type should be a valid type for each index
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  // in the range {0, 1, ..., _num - 1}. The \c VariantTypeMap is helper
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  // class to define such type mappings up to 10 types.
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  //
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  // And the usage of the class:
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  //\code
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  // typedef Variant<3, VariantTypeMap<int, std::string, double> > MyVariant;
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  // MyVariant var;
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  // var.set<0>(12);
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  // std::cout << var.get<0>() << std::endl;
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  // var.set<1>("alpha");
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  // std::cout << var.get<1>() << std::endl;
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  // var.set<2>(0.75);
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  // std::cout << var.get<2>() << std::endl;
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  //\endcode
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  //
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  // The result of course:
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  //\code
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  // 12
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  // alpha
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  // 0.75
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  //\endcode
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  template <int _num, typename _TypeMap>
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  class Variant {
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  public:
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    static const int num = _num;
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    typedef _TypeMap TypeMap;
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    // \brief Constructor
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    //
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    // This constructor initalizes to the default value of the \c type
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    // with 0 index.
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    Variant() {
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      flag = 0;
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      new(reinterpret_cast<typename TypeMap::template Map<0>::Type*>(data))
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        typename TypeMap::template Map<0>::Type();
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    }
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    // \brief Copy constructor
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    //
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    // Copy constructor
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    Variant(const Variant& variant) {
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      flag = variant.flag;
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      _variant_bits::Memory<num - 1, TypeMap>::copy(flag, data, variant.data);
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    }
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    // \brief Assign operator
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    //
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    // Assign operator
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    Variant& operator=(const Variant& variant) {
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      if (this == &variant) return *this;
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      _variant_bits::Memory<num - 1, TypeMap>::
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        destroy(flag, data);
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      flag = variant.flag;
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      _variant_bits::Memory<num - 1, TypeMap>::
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        copy(flag, data, variant.data);
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      return *this;
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    }
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    // \brief Destrcutor
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    //
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    // Destructor
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    ~Variant() {
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      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
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    }
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    // \brief Set to the default value of the type with \c _idx index.
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    //
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    // This function sets the variant to the default value of the
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    // type with \c _idx index.
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    template <int _idx>
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    Variant& set() {
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      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
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      flag = _idx;
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      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
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        typename TypeMap::template Map<_idx>::Type();
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      return *this;
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    }
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    // \brief Set to the given value of the type with \c _idx index.
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    //
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    // This function sets the variant to the given value of the type
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    // with \c _idx index.
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    template <int _idx>
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    Variant& set(const typename _TypeMap::template Map<_idx>::Type& init) {
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      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
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      flag = _idx;
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      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
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        typename TypeMap::template Map<_idx>::Type(init);
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      return *this;
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    }
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    // \brief Gets the current value of the type with \c _idx index.
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    //
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    // Gets the current value of the type with \c _idx index.
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    template <int _idx>
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    const typename TypeMap::template Map<_idx>::Type& get() const {
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      LEMON_DEBUG(_idx == flag, "Variant wrong index");
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      return *reinterpret_cast<const typename TypeMap::
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        template Map<_idx>::Type*>(data);
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    }
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    // \brief Gets the current value of the type with \c _idx index.
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    //
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    // Gets the current value of the type with \c _idx index.
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    template <int _idx>
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    typename _TypeMap::template Map<_idx>::Type& get() {
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      LEMON_DEBUG(_idx == flag, "Variant wrong index");
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      return *reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>
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        (data);
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    }
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    // \brief Returns the current state of the variant.
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    //
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    // Returns the current state of the variant.
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    int state() const {
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      return flag;
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    }
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  private:
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    char data[_variant_bits::Size<num - 1, TypeMap>::value];
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    int flag;
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  };
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  namespace _variant_bits {
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    template <int _index, typename _List>
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    struct Get {
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      typedef typename Get<_index - 1, typename _List::Next>::Type Type;
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    };
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    template <typename _List>
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    struct Get<0, _List> {
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      typedef typename _List::Type Type;
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    };
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    struct List {};
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    template <typename _Type, typename _List>
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    struct Insert {
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      typedef _List Next;
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      typedef _Type Type;
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    };
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    template <int _idx, typename _T0, typename _T1, typename _T2,
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              typename _T3, typename _T4, typename _T5, typename _T6,
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              typename _T7, typename _T8, typename _T9>
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    struct Mapper {
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      typedef List L10;
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      typedef Insert<_T9, L10> L9;
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      typedef Insert<_T8, L9> L8;
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      typedef Insert<_T7, L8> L7;
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      typedef Insert<_T6, L7> L6;
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      typedef Insert<_T5, L6> L5;
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      typedef Insert<_T4, L5> L4;
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      typedef Insert<_T3, L4> L3;
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      typedef Insert<_T2, L3> L2;
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      typedef Insert<_T1, L2> L1;
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      typedef Insert<_T0, L1> L0;
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      typedef typename Get<_idx, L0>::Type Type;
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   468
    };
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   470
  }
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  // \brief Helper class for Variant
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   473
  //
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  // Helper class to define type mappings for Variant. This class
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   475
  // converts the template parameters to be mappable by integer.
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   476
  // \see Variant
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   477
  template <
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   478
    typename _T0,
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   479
    typename _T1 = void, typename _T2 = void, typename _T3 = void,
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   480
    typename _T4 = void, typename _T5 = void, typename _T6 = void,
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   481
    typename _T7 = void, typename _T8 = void, typename _T9 = void>
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   482
  struct VariantTypeMap {
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   483
    template <int _idx>
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   484
    struct Map {
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   485
      typedef typename _variant_bits::
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   486
      Mapper<_idx, _T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9>::Type
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   487
      Type;
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   488
    };
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   489
  };
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   490
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   491
}
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   492
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   493
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   494
#endif