Function sum_field

include/ctrack.hpp:60–71

		template <typename T, typename Field>
		auto sum_field(const std::vector<T> &vec, Field T::*field)
		{
			using FieldType = std::decay_t<decltype(std::declval<T>().*field)>;
			return std::transform_reduce(
				OPT_EXEC_POLICY
					vec.begin(),
				vec.end(),
				FieldType{},
				std::plus<>(),
				[field](const auto &item)
				{ return item.*field; });
		}

		template <typename T, typename Field>
		auto sum_squared_field(const std::vector<T> &values, Field T::*field)