1.1 --- a/algs4-c++/src/Queue.hpp	Tue Jun 23 14:52:17 2015 -0500
     1.2 +++ b/algs4-c++/src/Queue.hpp	Tue Jun 23 15:27:26 2015 -0500
     1.3 @@ -6,6 +6,7 @@
     1.4  #include <cstddef>
     1.5  #include <cassert>
     1.6  #include <iterator>
     1.7 +#include <type_traits>
     1.8  
     1.9  template <typename T>
    1.10  class Queue {
    1.11 @@ -22,43 +23,54 @@
    1.12  public:
    1.13  
    1.14      ////////////////////////////////////
    1.15 -    class iterator : public std::iterator<std::forward_iterator_tag, T> {
    1.16 +
    1.17 +    template <bool is_const = true>
    1.18 +    class generic_iterator : public std::iterator<std::forward_iterator_tag, T> {
    1.19 +
    1.20 +    private:
    1.21 +        typedef typename std::conditional<is_const, const Node *, Node *>::type NodePtrType;
    1.22 +        typedef typename std::conditional<is_const, const T, T>::type ValueType;
    1.23  
    1.24      public:
    1.25  
    1.26 -        iterator( Node *c );
    1.27 +        generic_iterator( NodePtrType c ) :
    1.28 +            curr (c)
    1.29 +            {
    1.30 +            }
    1.31  
    1.32 -        iterator& operator++();
    1.33 -        iterator operator++(int);
    1.34 +        generic_iterator & operator++() {
    1.35 +            if ( this->curr != nullptr ) {
    1.36 +                this->curr = this->curr->next;
    1.37 +                }
    1.38 +            return *this;
    1.39 +            }
    1.40  
    1.41 -        T operator*();
    1.42 -        bool operator!=( typename Queue<T>::iterator );
    1.43 +        generic_iterator operator++( int ) {
    1.44 +            auto t = generic_iterator( *this );
    1.45 +
    1.46 +            if ( this->curr != nullptr ) {
    1.47 +                this->curr = this->curr->next;
    1.48 +                }
    1.49 +            return t;
    1.50 +            }
    1.51 +
    1.52 +        ValueType operator*() {
    1.53 +            return this->curr->item;
    1.54 +            }
    1.55 +
    1.56 +        bool operator!=( generic_iterator other ) {
    1.57 +            return this->curr != other.curr;
    1.58 +            }
    1.59  
    1.60      private:
    1.61  
    1.62 -        Node *curr;
    1.63 +        NodePtrType curr;
    1.64          };
    1.65  
    1.66      ////////////////////////////////////
    1.67  
    1.68 -    class const_iterator : public std::iterator<std::forward_iterator_tag, T> {
    1.69 -
    1.70 -    public:
    1.71 -
    1.72 -        const_iterator( const Node *c );
    1.73 -
    1.74 -        const_iterator& operator++();
    1.75 -        const_iterator operator++(int);
    1.76 -
    1.77 -        const T operator*();
    1.78 -        bool operator!=( typename Queue<T>::const_iterator );
    1.79 -
    1.80 -    private:
    1.81 -
    1.82 -        const Node *curr;
    1.83 -        };
    1.84 -
    1.85 -    ////////////////////////////////////
    1.86 +    typedef generic_iterator<true> const_iterator;
    1.87 +    typedef generic_iterator<false> iterator;
    1.88  
    1.89      Queue( void );
    1.90      ~Queue( void );
    1.91 @@ -182,79 +194,5 @@
    1.92      return Queue<T>::const_iterator( nullptr );
    1.93      }
    1.94  
    1.95 -
    1.96 -////////////////////////////////////////////////////////////////////////////////
    1.97 -
    1.98 -template <typename T>
    1.99 -Queue<T>::iterator::iterator( Node *c ) :
   1.100 -    curr (c)
   1.101 -    {
   1.102 -    }
   1.103 -
   1.104 -template <typename T>
   1.105 -typename Queue<T>::iterator & Queue<T>::iterator::operator++() {
   1.106 -    if ( this->curr != nullptr ) {
   1.107 -        this->curr = this->curr->next;
   1.108 -        }
   1.109 -    return *this;
   1.110 -    }
   1.111 -
   1.112 -template <typename T>
   1.113 -typename Queue<T>::iterator Queue<T>::iterator::operator++( int ) {
   1.114 -    auto t = Queue<T>::iterator( *this );
   1.115 -
   1.116 -    if ( this->curr != nullptr ) {
   1.117 -        this->curr = this->curr->next;
   1.118 -        }
   1.119 -    return t;
   1.120 -    }
   1.121 -
   1.122 -template <typename T>
   1.123 -T Queue<T>::iterator::operator*() {
   1.124 -    return this->curr->item;
   1.125 -    }
   1.126 -
   1.127 -template <typename T>
   1.128 -bool Queue<T>::iterator::operator!=( typename Queue<T>::iterator other ) {
   1.129 -    return this->curr != other.curr;
   1.130 -    }
   1.131 -
   1.132 -////////////////////////////////////////////////////////////////////////////////
   1.133 -
   1.134 -template <typename T>
   1.135 -Queue<T>::const_iterator::const_iterator( const Node *c ) :
   1.136 -    curr (c)
   1.137 -    {
   1.138 -    }
   1.139 -
   1.140 -template <typename T>
   1.141 -typename Queue<T>::const_iterator & Queue<T>::const_iterator::operator++() {
   1.142 -    if ( this->curr != nullptr ) {
   1.143 -        this->curr = this->curr->next;
   1.144 -        }
   1.145 -    return *this;
   1.146 -    }
   1.147 -
   1.148 -template <typename T>
   1.149 -typename Queue<T>::const_iterator Queue<T>::const_iterator::operator++( int ) {
   1.150 -    auto t = Queue<T>::const_iterator( *this );
   1.151 -
   1.152 -    if ( this->curr != nullptr ) {
   1.153 -        this->curr = this->curr->next;
   1.154 -        }
   1.155 -    return t;
   1.156 -    }
   1.157 -
   1.158 -template <typename T>
   1.159 -const T Queue<T>::const_iterator::operator*() {
   1.160 -    return this->curr->item;
   1.161 -    }
   1.162 -
   1.163 -template <typename T>
   1.164 -bool Queue<T>::const_iterator::operator!=( typename Queue<T>::const_iterator other ) {
   1.165 -    return this->curr != other.curr;
   1.166 -    }
   1.167 -
   1.168 -
   1.169  #endif
   1.170