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The C++ Standard Template Library STL as part of the C++ Standard Library provides a framework for processing algorithms on different kind of containers. However, ordinary arrays don't provide the interface of STL containers (although, they provide the iterator interface of STL containers).
As replacement for ordinary arrays, the STL provides class
    std::vector.  However,
    std::vector<> provides
    the semantics of dynamic arrays. Thus, it manages data to be able
    to change the number of elements. This results in some overhead in
    case only arrays with static size are needed.
In his book, Generic Programming and the
    STL, Matthew H. Austern introduces a useful wrapper
    class for ordinary arrays with static size, called
    block.  It is safer and has no worse performance than
    ordinary arrays. In The C++ Programming
    Language, 3rd edition, Bjarne Stroustrup introduces a
    similar class, called c_array, which I (Nicolai Josuttis) present
    slightly modified in my book The C++ Standard Library -
    A Tutorial and Reference, called
    carray. This is the essence of these approaches
    spiced with many feedback from boost.
After considering different names, we decided to name this
    class simply array.
Note that this class is suggested to be part of the next Technical Report, which will extend the C++ Standard (see http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1548.htm).
Class array fulfills most
    but not all of the requirements of "reversible containers" (see
    Section 23.1, [lib.container.requirements] of the C++
    Standard). The reasons array is not an reversible STL container is
    because:
      
swap() has no constant complexity.size() is always constant, based on the second template argument of the type.
It doesn't fulfill the requirements of a "sequence" (see Section 23.1.1, [lib.sequence.reqmts] of the C++ Standard), except that:
front() and back() are provided.operator[] and at() are provided.
namespace boost { template<typename T, std::size_t N> class array; template<typename T, std::size_t N> void swap(array<T, N>&, array<T, N>&); template<typename T, std::size_t N> bool operator==(const array<T, N>&, const array<T, N>&); template<typename T, std::size_t N> bool operator!=(const array<T, N>&, const array<T, N>&); template<typename T, std::size_t N> bool operator<(const array<T, N>&, const array<T, N>&); template<typename T, std::size_t N> bool operator>(const array<T, N>&, const array<T, N>&); template<typename T, std::size_t N> bool operator<=(const array<T, N>&, const array<T, N>&); template<typename T, std::size_t N> bool operator>=(const array<T, N>&, const array<T, N>&); }
There was an important design tradeoff regarding the constructors: We could implement array as an "aggregate" (see Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would mean:
An array can be initialized with a brace-enclosing, comma-separated list of initializers for the elements of the container, written in increasing subscript order:
               boost::array<int,4> a = { { 1, 2, 3 } };
            
Note that if there are fewer elements in the initializer list, then each remaining element gets default-initialized (thus, it has a defined value).
However, this approach has its drawbacks: passing no initializer list means that the elements have an indetermined initial value , because the rule says that aggregates may have:
Nevertheless, The current implementation uses this approach.
Note that for standard conforming compilers it is possible to use fewer braces (according to 8.5.1 (11) of the Standard). That is, you can initialize an array as follows:
      boost::array<int,4> a = { 1, 2, 3 };
   
I'd appreciate any constructive feedback. Please note: I don't have time to read all boost mails. Thus, to make sure that feedback arrives to me, please send me a copy of each mail regarding this class.
The code is provided "as is" without expressed or implied warranty.
To find more details about using ordinary arrays in C++ and the framework of the STL, see e.g.
         The C++ Standard Library - A Tutorial and Reference
         by Nicolai M. Josuttis
         Addison Wesley Longman, 1999
         ISBN 0-201-37926-0