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Move from boost-sanbox [ JDG ]
[SVN r18958]
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Joel de Guzman
193
include/boost/iterator/counting_iterator.hpp
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193
include/boost/iterator/counting_iterator.hpp
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// Copyright David Abrahams 2003. Permission to copy, use,
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// modify, sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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#ifndef COUNTING_ITERATOR_DWA200348_HPP
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# define COUNTING_ITERATOR_DWA200348_HPP
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# include <boost/iterator/iterator_adaptor.hpp>
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# include <boost/detail/numeric_traits.hpp>
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# include <boost/mpl/bool.hpp>
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# include <boost/mpl/if.hpp>
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# include <boost/mpl/identity.hpp>
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# include <boost/mpl/apply_if.hpp>
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namespace boost {
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template <class Incrementable, class Category, class Difference> class counting_iterator;
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namespace detail
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{
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// Try to detect numeric types at compile time in ways compatible
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// with the limitations of the compiler and library.
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template <class T>
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struct is_numeric_impl
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{
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// For a while, this wasn't true, but we rely on it below. This is a regression assert.
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BOOST_STATIC_ASSERT(::boost::is_integral<char>::value);
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# ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
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# if defined(BOOST_HAS_LONG_LONG)
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BOOST_STATIC_CONSTANT(
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bool, value = (
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std::numeric_limits<T>::is_specialized
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| boost::is_same<T,long long>::value
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| boost::is_same<T,unsigned long long>::value
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));
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# else
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BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<T>::is_specialized);
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# endif
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# else
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# if !defined(__BORLANDC__)
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BOOST_STATIC_CONSTANT(
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bool, value = (
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boost::is_convertible<int,T>::value
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&& boost::is_convertible<T,int>::value
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));
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# else
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BOOST_STATIC_CONSTANT(bool, value = ::boost::is_arithmetic<T>::value);
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# endif
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# endif
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};
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template <class T>
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struct is_numeric
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: mpl::bool_<(::boost::detail::is_numeric_impl<T>::value)>
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{};
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template <class T>
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struct numeric_difference
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{
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typedef typename boost::detail::numeric_traits<T>::difference_type type;
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};
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BOOST_STATIC_ASSERT(is_numeric<int>::value);
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template <class Incrementable, class Category, class Difference>
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struct counting_iterator_base
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{
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typedef typename mpl::apply_if<
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is_same<Category, use_default>
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, mpl::apply_if<
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is_numeric<Incrementable>
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, mpl::identity<std::random_access_iterator_tag>
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, BOOST_ITERATOR_CATEGORY<Incrementable>
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>
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, mpl::identity<Category>
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>::type category;
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typedef typename mpl::apply_if<
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is_same<Difference, use_default>
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, mpl::apply_if<
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is_numeric<Incrementable>
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, numeric_difference<Incrementable>
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, iterator_difference<Incrementable>
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>
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, mpl::identity<Difference>
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>::type difference;
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typedef iterator_adaptor<
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counting_iterator<Incrementable, Category, Difference> // self
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, Incrementable // Base
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, Incrementable // value_type
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, category
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, Incrementable const& // reference
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, difference
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> type;
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};
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// Template class distance_policy_select -- choose a policy for computing the
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// distance between counting_iterators at compile-time based on whether or not
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// the iterator wraps an integer or an iterator, using "poor man's partial
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// specialization".
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template <bool is_integer> struct distance_policy_select;
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// A policy for wrapped iterators
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template <class Difference, class Incrementable1, class Incrementable2>
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struct iterator_distance
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{
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static Difference distance(Incrementable1 x, Incrementable2 y)
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{
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return boost::detail::distance(x, y);
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}
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};
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// A policy for wrapped numbers
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template <class Difference, class Incrementable1, class Incrementable2>
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struct number_distance
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{
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static Difference distance(Incrementable1 x, Incrementable2 y)
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{
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return numeric_distance(x, y);
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}
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};
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}
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template <class Incrementable, class Category = use_default, class Difference = use_default>
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class counting_iterator
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: public detail::counting_iterator_base<Incrementable, Category, Difference>::type
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{
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typedef typename detail::counting_iterator_base<Incrementable, Category, Difference>::type super_t;
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friend class iterator_core_access;
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public:
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typedef typename super_t::difference_type difference_type;
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counting_iterator() { }
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counting_iterator(counting_iterator const& rhs) : super_t(rhs.base()) {}
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counting_iterator(Incrementable x)
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: super_t(x)
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{
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}
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# if 0
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template<class OtherIncrementable>
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counting_iterator(
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counting_iterator<OtherIncrementable> const& t
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, typename enable_if_convertible<OtherIncrementable, Incrementable>::type* = 0
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)
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: super_t(t.base())
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{}
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# endif
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private:
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typename super_t::reference dereference() const
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{
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return this->base_reference();
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}
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template <class OtherIncrementable>
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difference_type
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distance_to(counting_iterator<OtherIncrementable> const& y) const
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{
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typedef typename mpl::if_<
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detail::is_numeric<Incrementable>
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, detail::number_distance<difference_type, Incrementable, OtherIncrementable>
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, detail::iterator_distance<difference_type, Incrementable, OtherIncrementable>
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>::type d;
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return d::distance(this->base(), y.base());
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}
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};
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// Manufacture a counting iterator for an arbitrary incrementable type
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template <class Incrementable>
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inline counting_iterator<Incrementable>
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make_counting_iterator(Incrementable x)
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{
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typedef counting_iterator<Incrementable> result_t;
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return result_t(x);
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}
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} // namespace boost::iterator
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#endif // COUNTING_ITERATOR_DWA200348_HPP
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