mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-15 02:41:59 +00:00
78 lines
3.0 KiB
C++
78 lines
3.0 KiB
C++
#pragma once
|
|
|
|
#include <type_traits>
|
|
#include <utility>
|
|
#include <iterator>
|
|
|
|
/** \brief Numeric range iterator, used to represent a half-closed interval [begin, end).
|
|
* In conjunction with std::reverse_iterator allows for forward and backward iteration
|
|
* over corresponding interval. */
|
|
namespace ext
|
|
{
|
|
/// @todo check whether difference_type should be signed (make_signed_t<T>)
|
|
template<typename T> struct range_iterator : std::iterator<
|
|
std::bidirectional_iterator_tag, T, T, void, T>
|
|
{
|
|
T current{};
|
|
|
|
range_iterator() = default;
|
|
range_iterator(const T t) : current(t) {}
|
|
|
|
T operator*() const { return current; }
|
|
|
|
range_iterator & operator++() { return ++current, *this; }
|
|
range_iterator & operator--() { return --current, *this; }
|
|
|
|
bool operator==(const range_iterator & other) const { return current == other.current; }
|
|
bool operator!=(const range_iterator & other) const { return current != other.current; }
|
|
};
|
|
|
|
template<typename T> using reverse_range_iterator = std::reverse_iterator<range_iterator<T>>;
|
|
|
|
/** \brief Range-based for loop adapter for (reverse_)range_iterator.
|
|
* By and large should be in conjunction with ext::range and ext::reverse_range. */
|
|
template<typename T, bool forward> struct range_wrapper
|
|
{
|
|
using value_type = typename std::remove_reference<T>::type;
|
|
using range_iterator_t = ext::range_iterator<value_type>;
|
|
using iterator = typename std::conditional<forward,
|
|
range_iterator_t,
|
|
ext::reverse_range_iterator<value_type>>::type;
|
|
|
|
value_type begin_, end_;
|
|
|
|
iterator begin() const { return iterator(range_iterator_t{begin_}); }
|
|
iterator end() const { return iterator(range_iterator_t{end_}); }
|
|
};
|
|
|
|
/** \brief Constructs range_wrapper for forward-iteration over [begin, end) in range-based for loop.
|
|
* Usage example:
|
|
* for (const auto i : ext::range(0, 4)) print(i);
|
|
* Output:
|
|
* 0 1 2 3 */
|
|
template<typename T1, typename T2>
|
|
inline ext::range_wrapper<typename std::common_type<T1, T2>::type, true> range(T1 begin, T2 end)
|
|
{
|
|
using common_type = typename std::common_type<T1, T2>::type;
|
|
return { static_cast<common_type>(begin), static_cast<common_type>(end) };
|
|
}
|
|
|
|
/** \brief Constructs range_wrapper for backward-iteration over [begin, end) in range-based for loop.
|
|
* Usage example:
|
|
* for (const auto i : ext::reverse_range(0, 4)) print(i);
|
|
* Output:
|
|
* 3 2 1 0 */
|
|
template<typename T1, typename T2>
|
|
inline ext::range_wrapper<typename std::common_type<T1, T2>::type, false> reverse_range(T1 begin, T2 end)
|
|
{
|
|
using common_type = typename std::common_type<T1, T2>::type;
|
|
return { static_cast<common_type>(end), static_cast<common_type>(begin) };
|
|
}
|
|
|
|
template<typename T>
|
|
inline ext::range_iterator<T> make_range_iterator(const T value)
|
|
{
|
|
return { value };
|
|
}
|
|
}
|