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// Copyright David Abrahams 2003.
// 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)
#ifndef COUNTING_ITERATOR_DWA200348_HPP
# define COUNTING_ITERATOR_DWA200348_HPP
# include <boost/iterator/iterator_adaptor.hpp>
# include <boost/detail/numeric_traits.hpp>
# include <boost/mpl/bool.hpp>
# include <boost/mpl/if.hpp>
# include <boost/mpl/identity.hpp>
# include <boost/mpl/eval_if.hpp>
namespace boost {
namespace iterators {
template <
class Incrementable
, class CategoryOrTraversal
, class Difference
>
class counting_iterator;
namespace detail
{
// Try to detect numeric types at compile time in ways compatible
// with the limitations of the compiler and library.
template <class T>
struct is_numeric_impl
{
// For a while, this wasn't true, but we rely on it below. This is a regression assert.
BOOST_STATIC_ASSERT(::boost::is_integral<char>::value);
# ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<T>::is_specialized);
# else
# if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
BOOST_STATIC_CONSTANT(
bool, value = (
boost::is_convertible<int,T>::value
&& boost::is_convertible<T,int>::value
));
# else
BOOST_STATIC_CONSTANT(bool, value = ::boost::is_arithmetic<T>::value);
# endif
# endif
};
template <class T>
struct is_numeric
: mpl::bool_<(::boost::iterators::detail::is_numeric_impl<T>::value)>
{};
# if defined(BOOST_HAS_LONG_LONG)
template <>
struct is_numeric< ::boost::long_long_type>
: mpl::true_ {};
template <>
struct is_numeric< ::boost::ulong_long_type>
: mpl::true_ {};
# endif
// Some compilers fail to have a numeric_limits specialization
template <>
struct is_numeric<wchar_t>
: mpl::true_ {};
template <class T>
struct numeric_difference
{
typedef typename boost::detail::numeric_traits<T>::difference_type type;
};
BOOST_STATIC_ASSERT(is_numeric<int>::value);
template <class Incrementable, class CategoryOrTraversal, class Difference>
struct counting_iterator_base
{
typedef typename detail::ia_dflt_help<
CategoryOrTraversal
, mpl::eval_if<
is_numeric<Incrementable>
, mpl::identity<random_access_traversal_tag>
, iterator_traversal<Incrementable>
>
>::type traversal;
typedef typename detail::ia_dflt_help<
Difference
, mpl::eval_if<
is_numeric<Incrementable>
, numeric_difference<Incrementable>
, iterator_difference<Incrementable>
>
>::type difference;
typedef iterator_adaptor<
counting_iterator<Incrementable, CategoryOrTraversal, Difference> // self
, Incrementable // Base
, Incrementable // Value
# ifndef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
const // MSVC won't strip this. Instead we enable Thomas'
// criterion (see boost/iterator/detail/facade_iterator_category.hpp)
# endif
, traversal
, Incrementable const& // reference
, difference
> type;
};
// Template class distance_policy_select -- choose a policy for computing the
// distance between counting_iterators at compile-time based on whether or not
// the iterator wraps an integer or an iterator, using "poor man's partial
// specialization".
template <bool is_integer> struct distance_policy_select;
// A policy for wrapped iterators
template <class Difference, class Incrementable1, class Incrementable2>
struct iterator_distance
{
static Difference distance(Incrementable1 x, Incrementable2 y)
{
return y - x;
}
};
// A policy for wrapped numbers
template <class Difference, class Incrementable1, class Incrementable2>
struct number_distance
{
static Difference distance(Incrementable1 x, Incrementable2 y)
{
return boost::detail::numeric_distance(x, y);
}
};
}
template <
class Incrementable
, class CategoryOrTraversal = use_default
, class Difference = use_default
>
class counting_iterator
: public detail::counting_iterator_base<
Incrementable, CategoryOrTraversal, Difference
>::type
{
typedef typename detail::counting_iterator_base<
Incrementable, CategoryOrTraversal, Difference
>::type super_t;
friend class iterator_core_access;
public:
typedef typename super_t::difference_type difference_type;
counting_iterator() { }
counting_iterator(counting_iterator const& rhs) : super_t(rhs.base()) {}
counting_iterator(Incrementable x)
: super_t(x)
{
}
# if 0
template<class OtherIncrementable>
counting_iterator(
counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& t
, typename enable_if_convertible<OtherIncrementable, Incrementable>::type* = 0
)
: super_t(t.base())
{}
# endif
private:
typename super_t::reference dereference() const
{
return this->base_reference();
}
template <class OtherIncrementable>
difference_type
distance_to(counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& y) const
{
typedef typename mpl::if_<
detail::is_numeric<Incrementable>
, detail::number_distance<difference_type, Incrementable, OtherIncrementable>
, detail::iterator_distance<difference_type, Incrementable, OtherIncrementable>
>::type d;
return d::distance(this->base(), y.base());
}
};
// Manufacture a counting iterator for an arbitrary incrementable type
template <class Incrementable>
inline counting_iterator<Incrementable>
make_counting_iterator(Incrementable x)
{
typedef counting_iterator<Incrementable> result_t;
return result_t(x);
}
} // namespace iterators
using iterators::counting_iterator;
using iterators::make_counting_iterator;
} // namespace boost
#endif // COUNTING_ITERATOR_DWA200348_HPP
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