deque

Container

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
• Interface
• Constructors
• Destructors
• Allocators
• Iterators
• Assignment Operators
• Reference Operators
• Member Functions
• Non-member Functions
• Specialized Algorithms
• Example
• Warnings

A sequence that supports random access iterators and efficient insertion/deletion at both beginning and end.

Data Types

allocator

Member Functions
assign() at() back() begin() clear() empty() end()	erase() front() get_allocator() insert() max_size() operator!=() operator>()	operator>=() operator<() operator<=() operator=() operator==() operator[]() pop_back()	pop_front() push_back() push_front() rbegin() rend() resize() size() swap()

#include <deque>

template <class T, class Allocator = allocator<T> >
 class deque;

deque<T, Allocator> is a type of sequence that supports random access iterators. It supports constant time insert and erase operations at the beginning or the end of the container. Insertion and erase in the middle take linear time. Storage management is handled by the Allocator template parameter.

Any type used for the template parameter T must include the following (where T is the type, t is a value of T and u is a const value of T):

template <class T, class Allocator = allocator<T> >
 class deque {

public:

 // Types

   class iterator; 
   class const_iterator;

   typedef T value_type;
   typedef Allocator allocator_type;
   typedef typename
           Allocator::reference        reference;
   typedef typename
           Allocator::const_reference  const_reference;
   typedef typename
           Allocator::size_type        size_type;
   typedef typename
           Allocator::difference_type  difference_type;
   typedef typename
           std::reverse_iterator<iterator> reverse_iterator;
   typedef typename
           std::reverse_iterator<const_iterator>
                                 const_reverse_iterator;

 // Construct/Copy/Destroy

   explicit deque (const Allocator& = Allocator());
   explicit deque (size_type);
   deque (size_type, const T& value, 
          const Allocator& = Allocator ());
   deque (const deque<T,Allocator>&);
   template <class InputIterator>
    deque (InputIterator, InputIterator, 
           const Allocator& = Allocator ());
   ~deque ();
   deque<T,Allocator>& operator= 
                       (const deque<T,Allocator>&);
   template <class InputIterator>
    void assign (InputIterator, InputIterator);
   void assign (size_type, const T&);
   allocator_type get allocator () const;

 // Iterators

   iterator begin ();
   const_iterator begin () const;
   iterator end ();
   const_iterator end () const;
   reverse_iterator rbegin ();
   const_reverse_iterator rbegin () const;
   reverse_iterator rend ();
   const_reverse_iterator rend () const;

// Capacity

   size_type size () const;
   size_type max_size () const;
   void resize (size_type);
   void resize (size_type, T);
   bool empty () const;

// Element access

   reference operator[] (size_type);
   const_reference operator[] (size_type) const;
   reference at (size_type);
   const_reference at (size_type) const;
   reference front ();
   const_reference front () const;
   reference back ();
   const_reference back () const;

 // Modifiers

   void push_front (const T&);
   void push_back (const T&);
   iterator insert (iterator, const T&);
   void insert (iterator, size_type, const T&);
   template <class InputIterator>
    void insert (iterator, InputIterator, InputIterator);

   void pop_front ();
   void pop_back ();

   iterator erase (iterator);
   iterator erase (iterator, iterator);
   void swap (deque<T, Allocator>&);
   void clear();
};

 // Non-member Operators

template <class T, class Allocator>
 bool operator== (const deque<T, Allocator>&, 
                  const deque<T, Allocator>&);

template <class T, class Allocator>
 bool operator!= (const deque<T, Allocator>&, 
                  const deque<T, Allocator>&);


template <class T, class Allocator>
 bool operator< (const deque<T, Allocator>&, 
                 const deque<T, Allocator>&);

template <class T, class Allocator>
 bool operator> (const deque<T, Allocator>&, 
                 const deque<T, Allocator>&);

template <class T, class Allocator>
 bool operator<= (const deque<T, Allocator>&, 
                 const deque<T, Allocator>&);

template <class T, class Allocator>
 bool operator>= (const deque<T, Allocator>&, 
                 const deque<T, Allocator>&);


// Specialized Algorithms

template <class T, class Allocator>
 voice swap (deque<T, Allocator>&, deque<T, Allocator>&);

explicit 
deque(const Allocator& alloc = Allocator());

The default constructor. Creates a deque of zero elements. The deque uses the allocator alloc for all storage management.

explicit 
deque(size_type n);

Creates a list of length n, containing n copies of the default value for type T. T must have a default constructor. The deque uses the allocator Allocator() for all storage management.

deque(size_type n, const T& value, 
       const Allocator& alloc = Allocator());

Creates a list of length n, containing n copies of value. The deque uses the allocator alloc for all storage management.

deque(const deque<T, Allocator>& x);

Creates a copy of x.

template <class InputIterator>
deque(InputIterator first, InputIterator last, 
       const Allocator& alloc = Allocator());

Creates a deque of length last - first, filled with all values obtained by dereferencing the InputIterators on the range [first, last). The deque uses the allocator alloc for all storage management.

~deque();

Releases any allocated memory for self.

allocator
allocator_type get_allocator() const;

Returns a copy of the allocator used by self for storage management.

iterator begin();

Returns a random access iterator that points to the first element.

const_iterator begin() const;

Returns a constant random access iterator that points to the first element.

iterator end();

Returns a random access iterator that points to the past-the-end value.

const_iterator end() const;

Returns a constant random access iterator that points to the past-the-end value.

reverse_iterator rbegin();

Returns a random access reverse_iterator that points to the past-the-end value.

const_reverse_iterator rbegin() const;

Returns a constant random access reverse iterator that points to the past-the-end value.

reverse_iterator rend();

Returns a random access reverse_iterator that points to the first element.

const_reverse_iterator rend() const;

Returns a constant random access reverse iterator that points to the first element.

deque<T, Allocator>& 
operator=(const deque<T, Allocator>& x);

Erases all elements in self, then inserts into self a copy of each element in x. Returns a reference to self.

reference operator[](size_type n);

Returns a reference to element n of self. The result can be used as an lvalue. The index n must be between 0 and the size() - 1..

const_reference operator[](size_type n) const;

Returns a constant reference to element n of self. The index n must be between 0 and the size() - 1.

template <class InputIterator>
void
assign(InputIterator first, InputIterator last);

Erases all elements contained in self, then inserts new elements from the range [first, last).

void 
assign(size_type n, const T& t);

Erases all elements contained in self, then inserts n instances of the value of t.

reference 
at(size_type n);

Returns a reference to element n of self. The result can be used as an lvalue. The index n must be between 0 and the size() - 1.

const_reference 
at(size_type) const;

Returns a constant reference to element n of self. The index n must be between 0 and the size() - 1.

reference 
back();

Returns a reference to the last element.

const_reference 
back() const;

Returns a constant reference to the last element.

void
clear();

Erases all elements from the self.

bool 
empty() const;

Returns true if the size of self is zero.

reference 
front();

Returns a reference to the first element.

const_reference 
front() const;

Returns a constant reference to the first element.

iterator
erase(iterator first, iterator last);

Deletes the elements in the range (first, last). Returns an iterator pointing to the element following the last deleted element, or end() if there were no elements after the deleted range.

iterator
erase(iterator position);

Removes the element pointed to by position. Returns an iterator pointing to the element following the deleted element, or end() if there were no elements after the deleted range.

iterator 
insert(iterator position, const T& x);

Inserts x before position. The return value points to the inserted x.

void 
insert(iterator position, size_type n, const T& x);

Inserts n copies of x before position.

template <class InputIterator>
void 
insert(iterator position, InputIterator first,
        InputIterator last);

Inserts copies of the elements in the range (first, last] before position.

size_type 
max_size() const;

Returns size() of the largest possible deque.

void 
pop_back();

Removes the last element. Note that this function does not return the element.

void 
pop_front();

Removes the first element. Note that this function does not return the element.

void
push_back(const T& x);

Appends a copy of x to the end.

void 
push_front(const T& x);

Inserts a copy of x at the front.

void 
resize(size_type sz);

Alters the size of self. If the new size (sz) is greater than the current size, then sz-size() copies of the default value of type T are inserted at the end of the deque. If the new size is smaller than the current capacity, then the deque is truncated by erasing size()-sz elements off the end. Otherwise, no action is taken. Type T must have a default constructor.

void 
resize(size_type sz, T c);

Alters the size of self. If the new size (sz) is greater than the current size, then sz-size() c's are inserted at the end of the deque. If the new size is smaller than the current capacity, then the deque is truncated by erasing size()-sz elements off the end. Otherwise, no action is taken.

size_type 
size() const;

Returns the number of elements.

void 
swap(deque<T,Allocator>& x);

Exchanges self with x.

template <class T, class Allocator>
bool operator==(const deque<T, Allocator>& x,
                 const deque<T, Allocator>& y);

Equality operator. Returns true if x is the same as y.

template <class T, class Allocator>
bool operator!=(const deque<T, Allocator>& x,
                 const deque<T, Allocator>& y);

Returns true if x is not the same as y.

template <class T, class Allocator>
bool operator<(const deque<T, Allocator>& x,
                const deque<T, Allocator>& y);

Returns true if the elements contained in x are lexicographically less than the elements contained in y.

template <class T, class Allocator>
bool operator>(const deque<T, Allocator>& x,
                const deque<T, Allocator>& y);

Returns true if the elements contained in x are lexicographically greater than the elements contained in y.

template <class T, class Allocator>
bool operator<=(const deque<T, Allocator>& x,
                const deque<T, Allocator>& y);

Returns true if the elements contained in x are lexicographically less than or equal to the elements contained in y.

template <class T, class Allocator>
bool operator>=(const deque<T, Allocator>& x,
                const deque<T, Allocator>& y);

Returns true if the elements contained in x are lexicographically greater than or equal to the elements contained in y.

template <class T, class Allocator>
bool operator<(const deque<T, Allocator>& x,
                const deque<T, Allocator>& y);

Returns true if the elements contained in x are lexicographically less than the elements contained in y.

template <class T, class Allocator>
void swap(deque<T, Allocator>& a, deque<T, Allocator>& b);

Swaps the contents of a and b.

//
// deque.cpp
//
 #include <deque>
 #include <string>
 #include <iostream>
 using namespace std;

 deque<string, allocator> deck_of_cards; 
 deque<string, allocator> current_hand;

 void initialize_cards(deque<string, allocator>& cards) {
   cards.push_front("aceofspades");
   cards.push_front("kingofspades");
   cards.push_front("queenofspades");
   cards.push_front("jackofspades");
   cards.push_front("tenofspades");
   // etc.
 }

 template <class It, class It2> 
 void print_current_hand(It start, It2 end) 
 {
   while (start < end) 
   cout << *start++ << endl;
 }


 template <class It, class It2>
 void deal_cards(It, It2 end) {
   for (int i=0;i<5;i++) {
     current_hand.insert(current_hand.begin(),*end);
     deck_of_cards.erase(end++);
   }
 }

 void play_poker() {
   initialize_cards(deck_of_cards);
   deal_cards(current_hand.begin(),deck_of_cards.begin()); 
 }

 int main() 
 {
   play_poker();
   print_current_hand(current_hand.begin(),current_hand.end());
   return 0;
 }

Program Output

aceofspades
kingofspades
queenofspades
jackofspades
tenofspades

Member function templates are used in all containers in by the Standard Template Library. An example of this is the constructor for deque<T, Allocator>, which takes two templatized iterators:

template <class InputIterator>
 deque (InputIterator, InputIterator);

deque also has an insert function of this type. These functions, when not restricted by compiler limitations, allow you to use any type of input iterator as arguments. For compilers that do not support this feature, substitute functions allow you to use an iterator obtained from the same type of container as the one you are constructing (or calling a member function on), or you can use a pointer to the type of element you have in the container.

For example, if your compiler does not support member function templates you can construct a deque in the following two ways:

int intarray[10];
deque<int> first_deque(intarray, intarray + 10);
deque<int> second_deque(first_deque.begin(), 
                        first_deque.end());

But not this way:

deque<long> long_deque(first_deque.begin(), 
                                  first_deque.end());

since the long_deque and first_deque are not the same type.

Additionally, many compilers do not support default template arguments. If your compiler is one of these, you always need to supply the Allocator template argument. For instance, you have to write:

deque<int, allocator<int> >

instead of:

deque<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.