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iterator: remove index_type trait

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This was used primarily for iteration over map-like objects but it never
turned out to be terrifically robust, and encouraged users to either
conflate index types or to ham-fist the conversions.

It's better to be slightly less ergonomic and reliable than to be more
ergonomic and introduce the possibility for errors.
This commit is contained in:
Danny Robson 2018-10-01 15:35:30 +10:00
parent 6dede936bd
commit 06d7d2840d
1 changed files with 3 additions and 21 deletions
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24
iterator.hpp
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@ -221,29 +221,11 @@ namespace cruft {
} }
///////////////////////////////////////////////////////////////////////////
/// a trait that stores a type suitable for indexing a container
template <typename, typename = std::void_t<>>
struct index_type { using type = std::size_t; };
//-------------------------------------------------------------------------
template <typename ContainerT>
struct index_type<
ContainerT,
std::void_t<
typename ContainerT::index_t
>
> {
using type = typename ContainerT::index_t;
};
/////////////////////////////////////////////////////////////////////////// ///////////////////////////////////////////////////////////////////////////
template <typename ContainerT> template <typename ContainerT>
class indices { class indices {
public: public:
using value_type = typename index_type<ContainerT>::type; using value_type = std::size_t;
indices (const ContainerT &_container): indices (const ContainerT &_container):
m_container (_container) m_container (_container)
@ -286,8 +268,8 @@ namespace cruft {
value_type m_index; value_type m_index;
}; };
iterator begin (void) const { return iterator { value_type {0} }; } iterator begin (void) const { return iterator { value_type {0} }; }
iterator end (void) const { return iterator { value_type (m_container.size ()) }; } iterator end (void) const { return iterator { m_container.size () }; }
constexpr auto size (void) const noexcept constexpr auto size (void) const noexcept
{ {