Add util::array iterators over range of indices

libs/util/include/psemek/util/array.hpp

@@ -96,6 +96,10 @@ namespace psemek::util
 
 		void fill(T const & value);
 
+		auto index_begin() const;
+		auto index_end() const;
+		auto indices() const;
+
 	private:
 		std::unique_ptr<T[]> data_;
 		std::array<std::size_t, N> dims_;
@@ -148,6 +152,75 @@ namespace psemek::util
 			return false;
 		}
 
+		template <std::size_t N>
+		struct array_index_iterator
+		{
+			std::array<std::size_t, N> idx;
+			std::array<std::size_t, N> dims;
+
+			bool end;
+
+			std::array<std::size_t, N> const & operator*() const { return idx; }
+
+			array_index_iterator & operator ++()
+			{
+				end = next(idx, dims);
+				return *this;
+			}
+		};
+
+		struct array_index_iterator_sentinel
+		{};
+
+		template <std::size_t N>
+		bool operator == (array_index_iterator<N> const & it, array_index_iterator_sentinel)
+		{
+			return it.end;
+		}
+
+		template <std::size_t N>
+		bool operator != (array_index_iterator<N> const & it, array_index_iterator_sentinel)
+		{
+			return !it.end;
+		}
+
+		template <std::size_t N>
+		struct array_index_range
+		{
+			std::array<std::size_t, N> dims;
+
+			array_index_iterator<N> begin() const
+			{
+				std::array<std::size_t, N> idx;
+				for (std::size_t i = 0; i < N; ++i)
+					idx[i] = 0;
+				return {idx, dims, false};
+			}
+
+			array_index_iterator_sentinel end() const
+			{
+				return {};
+			}
+		};
+
+	}
+
+	template <typename T, std::size_t N>
+	auto array<T, N>::index_begin() const
+	{
+		return indices().begin();
+	}
+
+	template <typename T, std::size_t N>
+	auto array<T, N>::index_end() const
+	{
+		return indices().end();
+	}
+
+	template <typename T, std::size_t N>
+	auto array<T, N>::indices() const
+	{
+		return detail::array_index_range<N>{dims_};
 	}
 
 	template <typename T, std::size_t N>