# Pointer Container Library

# Class `ptr_deque`

A `ptr_deque<T>` is a pointer container that uses an underlying `std:deque<void*>` to store the pointers.

See also:

- reversible_ptr_container
- ptr_sequence_adapter

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Synopsis:

    namespace boost
    {

        template
        <
            class T,
            class CloneAllocator = heap_clone_allocator
            class Allocator      = std::allocator<void*>
        >
        class ptr_deque : public ptr_sequence_adapter
                                 <
                                    T,
                                    std::deque<void*,Allocator>,
                                    CloneAllocator
                                 >
        {

        public: // element access
            T&        operator[]( size_type n );
            const T&  operator[]( size_type n ) const;
            T&        at( size_type n );
            const T&  at( size_type n ) const;

        public: // modifiers
            void      push_front( T* x );
            auto_type pop_front();

        public: // pointer container requirements
           auto_type replace( size_type idx, T* x );
           bool      is_null( size_type idx ) const;

        };

    } // namespace 'boost'

# Semantics

## Semantics: modifiers

- `void push_front( T* x );`

  > - Requirements: `x != 0`
  > - Effects: Inserts the pointer into container and takes ownership of it
  > - Throws: `bad_pointer` if `x == 0`
  > - Exception safety: Strong guarantee

- `auto_type pop_front():`

  > - Requirements:`not empty()`
  > - Effects: Removes the first element in the container
  > - Postconditions: `size()` is one less
  > - Throws: `bad_ptr_container_operation` if `empty() == true`
  > - Exception safety: Strong guarantee

## Semantics: element access

- `T& operator[]( size_type n );`

- `const T& operator[]( size_type n ) const;`

  > - Requirements: `n < size()`
  > - Effects: Returns a reference to the `n`'th element
  > - Throws: Nothing

- `T& at( size_type n );`

- `const T& at( size_type n ) const;`

  > - Requirements: `n < size()`
  > - Effects: Returns a reference to the `n`'th element
  > - Throws: `bad_index` if `n >=size()`

## Semantics: pointer container requirements

- `auto_type replace( size_type idx, T* x );`

  > - Requirements: `` x != 0 and idx < size()``
  > - Effects: returns the object indexed by `idx` and replaces it with `x`.
  > - Throws: `bad_index` if `idx >= size()` and `bad_pointer` if `x == 0`.
  > - Exception safety: Strong guarantee

- `bool is_null( size_type idx ) const;`

  > - Requirements: `idx < size()`
  > - Effects: returns whether the pointer at index `idx` is null
  > - Exception safety: Nothrow guarantee

copyright: | Thorsten Ottosen 2004-2005.