// Copyright (C) 2019 T. Zachary Laine
|
//
|
// 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 BOOST_STL_INTERFACES_REVERSE_ITERATOR_HPP
|
#define BOOST_STL_INTERFACES_REVERSE_ITERATOR_HPP
|
|
#include <boost/stl_interfaces/iterator_interface.hpp>
|
|
|
namespace boost { namespace stl_interfaces { inline namespace v1 {
|
|
namespace v1_dtl {
|
template<typename Iter>
|
constexpr auto ce_dist(Iter f, Iter l, std::random_access_iterator_tag)
|
-> decltype(l - f)
|
{
|
return l - f;
|
}
|
template<typename Iter, typename Tag>
|
constexpr auto ce_dist(Iter f, Iter l, Tag)
|
-> decltype(std::distance(f, l))
|
{
|
decltype(std::distance(f, l)) retval = 0;
|
for (; f != l; ++f) {
|
++retval;
|
}
|
return retval;
|
}
|
|
template<typename Iter>
|
constexpr Iter ce_prev(Iter it)
|
{
|
return --it;
|
}
|
|
template<typename Iter, typename Offset>
|
constexpr void
|
ce_adv(Iter & f, Offset n, std::random_access_iterator_tag)
|
{
|
f += n;
|
}
|
template<typename Iter, typename Offset, typename Tag>
|
constexpr void ce_adv(Iter & f, Offset n, Tag)
|
{
|
if (0 < n) {
|
for (Offset i = 0; i < n; ++i) {
|
++f;
|
}
|
} else {
|
for (Offset i = 0; i < -n; ++i) {
|
--f;
|
}
|
}
|
}
|
}
|
|
/** This type is very similar to the C++20 version of
|
`std::reverse_iterator`; it is `constexpr`-, `noexcept`-, and
|
proxy-friendly. */
|
template<typename BidiIter>
|
struct reverse_iterator
|
: iterator_interface<
|
reverse_iterator<BidiIter>,
|
#if 201703L < __cplusplus && defined(__cpp_lib_ranges)
|
typename v2::detail::iter_concept_t<BidiIter>,
|
#else
|
typename std::iterator_traits<BidiIter>::iterator_category,
|
#endif
|
typename std::iterator_traits<BidiIter>::value_type,
|
typename std::iterator_traits<BidiIter>::reference,
|
typename std::iterator_traits<BidiIter>::pointer,
|
typename std::iterator_traits<BidiIter>::difference_type>
|
{
|
constexpr reverse_iterator() noexcept(noexcept(BidiIter())) : it_() {}
|
constexpr reverse_iterator(BidiIter it) noexcept(
|
noexcept(BidiIter(it))) :
|
it_(it)
|
{}
|
template<
|
typename BidiIter2,
|
typename E = std::enable_if_t<
|
std::is_convertible<BidiIter2, BidiIter>::value>>
|
reverse_iterator(reverse_iterator<BidiIter2> const & it) : it_(it.it_)
|
{}
|
|
friend BOOST_STL_INTERFACES_HIDDEN_FRIEND_CONSTEXPR auto
|
operator-(reverse_iterator lhs, reverse_iterator rhs) noexcept(
|
noexcept(v1_dtl::ce_dist(
|
lhs.it_,
|
rhs.it_,
|
typename std::iterator_traits<BidiIter>::iterator_category{})))
|
{
|
return -v1_dtl::ce_dist(
|
rhs.it_,
|
lhs.it_,
|
typename std::iterator_traits<BidiIter>::iterator_category{});
|
}
|
|
constexpr typename std::iterator_traits<BidiIter>::reference
|
operator*() const noexcept(
|
noexcept(std::prev(v1_dtl::ce_prev(std::declval<BidiIter &>()))))
|
{
|
return *v1_dtl::ce_prev(it_);
|
}
|
|
constexpr reverse_iterator & operator+=(
|
typename std::iterator_traits<BidiIter>::difference_type
|
n) noexcept(noexcept(v1_dtl::
|
ce_adv(
|
std::declval<BidiIter &>(),
|
-n,
|
typename std::iterator_traits<
|
BidiIter>::
|
iterator_category{})))
|
{
|
v1_dtl::ce_adv(
|
it_,
|
-n,
|
typename std::iterator_traits<BidiIter>::iterator_category{});
|
return *this;
|
}
|
|
constexpr BidiIter base() const noexcept { return it_; }
|
|
private:
|
friend access;
|
constexpr BidiIter & base_reference() noexcept { return it_; }
|
constexpr BidiIter const & base_reference() const noexcept
|
{
|
return it_;
|
}
|
|
template<typename BidiIter2>
|
friend struct reverse_iterator;
|
|
BidiIter it_;
|
};
|
|
template<typename BidiIter>
|
constexpr auto operator==(
|
reverse_iterator<BidiIter> lhs,
|
reverse_iterator<BidiIter>
|
rhs) noexcept(noexcept(lhs.base() == rhs.base()))
|
-> decltype(rhs.base() == lhs.base())
|
{
|
return lhs.base() == rhs.base();
|
}
|
|
template<typename BidiIter1, typename BidiIter2>
|
constexpr auto operator==(
|
reverse_iterator<BidiIter1> lhs,
|
reverse_iterator<BidiIter2>
|
rhs) noexcept(noexcept(lhs.base() == rhs.base()))
|
-> decltype(rhs.base() == lhs.base())
|
{
|
return lhs.base() == rhs.base();
|
}
|
|
/** Makes a `reverse_iterator<BidiIter>` from an iterator of type
|
`Bidiiter`. */
|
template<typename BidiIter>
|
auto make_reverse_iterator(BidiIter it)
|
{
|
return reverse_iterator<BidiIter>(it);
|
}
|
|
}}}
|
|
|
#if 201703L < __cplusplus && defined(__cpp_lib_concepts) || \
|
defined(BOOST_STL_INTERFACES_DOXYGEN)
|
|
namespace boost { namespace stl_interfaces { namespace v2 {
|
|
/** A template alias for `std::reverse_iterator`. This only exists to
|
make migration from Boost.STLInterfaces to C++20 easier; switch to the
|
one in `std` as soon as you can. */
|
template<typename BidiIter>
|
using reverse_iterator = std::reverse_iterator<BidiIter>;
|
|
|
/** Makes a `reverse_iterator<BidiIter>` from an iterator of type
|
`Bidiiter`. This only exists to make migration from
|
Boost.STLInterfaces to C++20 easier; switch to the one in `std` as
|
soon as you can. */
|
template<typename BidiIter>
|
auto make_reverse_iterator(BidiIter it)
|
{
|
return reverse_iterator<BidiIter>(it);
|
}
|
|
}}}
|
|
#endif
|
|
#endif
|
