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 //////////////////////////////////////////////////////////////////////////////
 //
 // (C) Copyright Ion Gaztanaga 2011-2013. Distributed under the Boost
 // Software License, Version 1.0. (See accompanying file
 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 // See http://www.boost.org/libs/container for documentation.
 //
 //////////////////////////////////////////////////////////////////////////////
 
 #ifndef BOOST_CONTAINER_USES_ALLOCATOR_HPP
 #define BOOST_CONTAINER_USES_ALLOCATOR_HPP
 
 #include <boost/container/uses_allocator_fwd.hpp>
 #include <boost/container/detail/type_traits.hpp>
 
 namespace boost {
 namespace container {
 
 //! <b>Remark</b>: if a specialization constructible_with_allocator_suffix<X>::value is true, indicates that T may be constructed
 //! with an allocator as its last constructor argument.  Ideally, all constructors of T (including the
 //! copy and move constructors) should have a variant that accepts a final argument of
 //! allocator_type.
 //!
 //! <b>Requires</b>: if a specialization constructible_with_allocator_suffix<X>::value is true, T must have a nested type,
 //! allocator_type and at least one constructor for which allocator_type is the last
 //! parameter.  If not all constructors of T can be called with a final allocator_type argument,
 //! and if T is used in a context where a container must call such a constructor, then the program is
 //! ill-formed.
 //!
 //! <code>
 //!  template <class T, class Allocator = allocator<T> >
 //!  class Z {
 //!    public:
 //!      typedef Allocator allocator_type;
 //!
 //!    // Default constructor with optional allocator suffix
 //!    Z(const allocator_type& a = allocator_type());
 //!
 //!    // Copy constructor and allocator-extended copy constructor
 //!    Z(const Z& zz);
 //!    Z(const Z& zz, const allocator_type& a);
 //! };
 //!
 //! // Specialize trait for class template Z
 //! template <class T, class Allocator = allocator<T> >
 //! struct constructible_with_allocator_suffix<Z<T,Allocator> >
 //! { static const bool value = true;  };
 //! </code>
 //!
 //! <b>Note</b>: This trait is a workaround inspired by "N2554: The Scoped A Model (Rev 2)"
 //! (Pablo Halpern, 2008-02-29) to backport the scoped allocator model to C++03, as
 //! in C++03 there is no mechanism to detect if a type can be constructed from arbitrary arguments.
 //! Applications aiming portability with several compilers should always define this trait.
 //!
 //! In conforming C++11 compilers or compilers supporting SFINAE expressions
 //! (when BOOST_NO_SFINAE_EXPR is NOT defined), this trait is ignored and C++11 rules will be used
 //! to detect if a type should be constructed with suffix or prefix allocator arguments.
 template <class T>
 struct constructible_with_allocator_suffix
 {  static const bool value = false; };
 
 //! <b>Remark</b>: if a specialization constructible_with_allocator_prefix<X>::value is true, indicates that T may be constructed
 //! with allocator_arg and T::allocator_type as its first two constructor arguments.
 //! Ideally, all constructors of T (including the copy and move constructors) should have a variant
 //! that accepts these two initial arguments.
 //!
 //! <b>Requires</b>: specialization constructible_with_allocator_prefix<X>::value is true, T must have a nested type,
 //! allocator_type and at least one constructor for which allocator_arg_t is the first
 //! parameter and allocator_type is the second parameter.  If not all constructors of T can be
 //! called with these initial arguments, and if T is used in a context where a container must call such
 //! a constructor, then the program is ill-formed.
 //!
 //! <code>
 //! template <class T, class Allocator = allocator<T> >
 //! class Y {
 //!    public:
 //!       typedef Allocator allocator_type;
 //!
 //!       // Default constructor with and allocator-extended default constructor
 //!       Y();
 //!       Y(allocator_arg_t, const allocator_type& a);
 //!
 //!       // Copy constructor and allocator-extended copy constructor
 //!       Y(const Y& yy);
 //!       Y(allocator_arg_t, const allocator_type& a, const Y& yy);
 //!
 //!       // Variadic constructor and allocator-extended variadic constructor
 //!       template<class ...Args> Y(Args&& args...);
 //!       template<class ...Args>
 //!       Y(allocator_arg_t, const allocator_type& a, BOOST_FWD_REF(Args)... args);
 //! };
 //!
 //! // Specialize trait for class template Y
 //! template <class T, class Allocator = allocator<T> >
 //! struct constructible_with_allocator_prefix<Y<T,Allocator> >
 //! { static const bool value = true;  };
 //!
 //! </code>
 //!
 //! <b>Note</b>: This trait is a workaround inspired by "N2554: The Scoped Allocator Model (Rev 2)"
 //! (Pablo Halpern, 2008-02-29) to backport the scoped allocator model to C++03, as
 //! in C++03 there is no mechanism to detect if a type can be constructed from arbitrary arguments.
 //! Applications aiming portability with several compilers should always define this trait.
 //!
 //! In conforming C++11 compilers or compilers supporting SFINAE expressions
 //! (when BOOST_NO_SFINAE_EXPR is NOT defined), this trait is ignored and C++11 rules will be used
 //! to detect if a type should be constructed with suffix or prefix allocator arguments.
 template <class T>
 struct constructible_with_allocator_prefix
 {  static const bool value = false; };
 
 #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
 
 namespace dtl {
 
 template<typename T, typename Allocator>
 struct uses_allocator_imp
 {
    // Use SFINAE (Substitution Failure Is Not An Error) to detect the
    // presence of an 'allocator_type' nested type convertilble from Allocator.
    private:
    typedef char yes_type;
    struct no_type{ char dummy[2]; };
 
    // Match this function if T::allocator_type exists and is
    // implicitly convertible from Allocator
    template <class U>
    static yes_type test(typename U::allocator_type);
 
    // Match this function if T::allocator_type exists and it's type is `erased_type`.
    template <class U, class V>
    static typename dtl::enable_if
       < dtl::is_same<typename U::allocator_type, erased_type>
       , yes_type
       >::type  test(const V&);
 
    // Match this function if TypeT::allocator_type does not exist or is
    // not convertible from Allocator.
    template <typename U>
    static no_type test(...);
    static Allocator alloc;  // Declared but not defined
 
    public:
    static const bool value = sizeof(test<T>(alloc)) == sizeof(yes_type);
 };
 
 }  //namespace dtl {
 
 #endif   //#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
 
 //! <b>Remark</b>: Automatically detects whether T has a nested allocator_type that is convertible from
 //! Allocator. Meets the BinaryTypeTrait requirements ([meta.rqmts] 20.4.1). A program may
 //! specialize this type to define uses_allocator<X>::value as true for a T of user-defined type if T does not
 //! have a nested allocator_type but is nonetheless constructible using the specified Allocator where either:
 //! the first argument of a constructor has type allocator_arg_t and the second argument has type Alloc or
 //! the last argument of a constructor has type Alloc.
 //!
 //! <b>Result</b>: uses_allocator<T, Allocator>::value== true if a type T::allocator_type
 //! exists and either is_convertible<Alloc, T::allocator_type>::value != false or T::allocator_type
 //! is an alias `erased_type`. False otherwise.
 template <typename T, typename Allocator>
 struct uses_allocator
    : dtl::uses_allocator_imp<T, Allocator>
 {};
 
 }} //namespace boost::container
 
 #endif   //BOOST_CONTAINER_USES_ALLOCATOR_HPP

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