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Fix InputIterator overloads

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This commit is contained in:
Krystian Stasiowski
2019-12-30 21:12:20 -05:00
parent 094c698541
commit 5845a73275
3 changed files with 221 additions and 38 deletions
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53
include/boost/static_string/detail/static_string.hpp
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@ -31,13 +31,6 @@ using static_string = basic_static_string<N, char, std::char_traits<char>>;
template<std::size_t N>
using static_wstring = basic_static_string<N, wchar_t, std::char_traits<wchar_t>>;
// At minimum an integral type shall not qualify as an iterator (Agustin Berge)
// Applicable standardese: http://eel.is/c++draft/containers#container.requirements.general-17
template<class T>
using is_input_iterator =
std::integral_constant<bool,
! std::is_integral<T>::value>;
// Find the smallest width integral type that can hold a value as large as N (Glen Fernandes)
template<std::size_t N>
using smallest_width =
@ -74,15 +67,51 @@ struct is_nothrow_convertible<From, To, typename std::enable_if<
template<typename...>
using void_t = void;
// Check if iterator can do subtraction, meaning its random access
// Simplified check for if a type is an iterator
template<class T, typename = void>
struct is_iterator : std::false_type { };
template<class T>
struct is_iterator<T,
void_t<typename T::difference_type,
typename T::value_type,
typename T::pointer,
typename T::reference,
typename T::iterator_category>>
: std::true_type { };
template<class T>
struct is_iterator<T*, void>
: std::true_type { };
template<class T, typename = void>
struct is_input_iterator : std::false_type { };
template<class T>
struct is_input_iterator<T, typename std::enable_if<is_iterator<T>::value &&
std::is_convertible<typename std::iterator_traits<T>::iterator_category,
std::input_iterator_tag>::value>::type>
: std::true_type { };
template<class T, typename = void>
struct is_forward_iterator : std::false_type { };
template<class T>
struct is_forward_iterator<T, typename std::enable_if<is_iterator<T>::value &&
std::is_convertible<typename std::iterator_traits<T>::iterator_category,
std::forward_iterator_tag>::value>::type>
: std::true_type { };
template<typename T, typename = void>
struct is_difference_iter : std::false_type { };
struct is_subtractable
: std::false_type { };
template<typename T>
struct is_difference_iter<T, void_t<decltype(std::declval<T>() - std::declval<T>())>> : std::true_type { };
struct is_subtractable<T, void_t<decltype(std::declval<T&>() - std::declval<T&>())>>
: std::true_type { };
// constexpr distance for c++14
template<typename InputIt, typename std::enable_if<!is_difference_iter<InputIt>::value>::type* = nullptr>
template<typename InputIt, typename std::enable_if<!is_subtractable<InputIt>::value>::type* = nullptr>
BOOST_STATIC_STRING_CPP14_CONSTEXPR
typename std::iterator_traits<InputIt>::difference_type
distance(InputIt first, InputIt last)
@ -92,7 +121,7 @@ distance(InputIt first, InputIt last)
return dist;
}
template<typename RandomIt, typename std::enable_if<is_difference_iter<RandomIt>::value>::type* = nullptr>
template<typename RandomIt, typename std::enable_if<is_subtractable<RandomIt>::value>::type* = nullptr>
BOOST_STATIC_STRING_CPP14_CONSTEXPR
typename std::iterator_traits<RandomIt>::difference_type
distance(RandomIt first, RandomIt last)