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#pragma once
#include <array>
#include <cstddef>
#include <initializer_list>
#include <vector>
template<class T>
struct Span
{
public:
using element_type = T;
using pointer = T*;
using reference = T&;
using iterator = T*;
constexpr Span() noexcept : m_ptr(nullptr), m_count(0) {}
constexpr Span(std::nullptr_t) noexcept : Span() {}
constexpr Span(T* ptr, size_t count) noexcept : m_ptr(ptr), m_count(count) {}
constexpr Span(T* ptr_begin, T* ptr_end) noexcept : m_ptr(ptr_begin), m_count(ptr_end - ptr_begin) {}
constexpr Span(std::initializer_list<T> l) noexcept : m_ptr(l.begin()), m_count(l.size()) {}
template<size_t N>
constexpr Span(T (&arr)[N]) noexcept : Span(arr, N)
{
}
Span(std::vector<T>& v) noexcept : Span(v.data(), v.size()) {}
Span(const std::vector<std::remove_const_t<T>>& v) noexcept : Span(v.data(), v.size()) {}
constexpr iterator begin() const { return m_ptr; }
constexpr iterator end() const { return m_ptr + m_count; }
constexpr reference operator[](size_t i) const { return m_ptr[i]; }
constexpr size_t size() const { return m_count; }
private:
pointer m_ptr;
size_t m_count;
};
template<class T>
Span<T> make_span(std::vector<T>& v)
{
return {v.data(), v.size()};
}
template<class T>
Span<const T> make_span(const std::vector<T>& v)
{
return {v.data(), v.size()};
}
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