Container
A sequence that supports random access iterators and efficient insertion/deletion at both beginning and end.
#include <deque>
template <class T, class Allocator = allocator> 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 provide the following (where T is the type, t is a value of T and u is a const value of T):
| Default constructor | T() |
| Copy constructors | T(t) and T(u) |
| Destructor | t.~T() |
| Address of | &t and &u yielding T* and const T* respectively |
| Assignment | t = a where a is a (possibly const) value of T |
template <class T, class Allocator = allocator>
class deque {
public:
// Types
class iterator;
class const_iterator;
typedef T value_type;
typedef Allocator allocator_type;
typename reference;
typename const_reference;
typename size_type;
typename difference_type;
typename reverse_iterator;
typename const_reverse_iterator;
// Construct/Copy/Destroy
explicit deque (const Allocator& = Allocator());
explicit deque (size_type, const Allocator& = Allocator ());
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);
template <class Size, class T>
void assign (Size);
template <class Size, class T>
void assign (Size, 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);
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>&);
// 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 will use the allocator alloc for all storage management.
explicit deque (size_type n, const Allocator& alloc = Allocator());
Creates a list of length n, containing n copies of the default value for type T. Requires that T have a default constructor. The deque will use the allocator alloc 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 will use the allocator alloc for all storage management.
deque (const deque<T, Allocator>& x);
Copy constructor. 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 will use the allocator alloc for all storage management.
~deque ();
The destructor. 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 less one.
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).
template <class Size, class T> void assign (Size n);
Erases all elements contained in self, then inserts n instances of the default value of type T.
template <class Size, class T> void assign (Size 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);
Inserts a copy of the default value of type T before position. The return value points to the inserted element. Requires that type T have a default constructor.
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. Requires that type T 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 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);
Efficiently swaps the contents of a and b.
//
// deque.cpp
//
#include <deque>
#include <string>
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;
}
Output :
aceofspades
kingofspades
queenofspades
jackofspades
tenofspades
Member function templates are used in all containers provided by the Standard Template Library. An example of this is the constructor for deque<T, Allocator> that takes two templated 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 we provide substitute functions that 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, allocator> first_deque(intarray, intarray + 10);
deque<int, allocator> second_deque(first_deque.begin(),
first_deque.end());
But not this way:
deque<long, allocator> 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 need to always supply the Allocator template argument. For instance, you'll have to write:
deque<int, allocator>
instead of:
deque<int>