valarray.hpp

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            {                                                                           \
                return left Op numeric::promote<std::valarray<right_value_type> >(right);\
            }                                                                           \
        };

        BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP(plus, +)
        BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP(minus, -)
        BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP(multiplies, *)
        BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP(divides, /)
        BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP(modulus, %)

    #undef BOOST_NUMERIC_FUNCTIONAL_DEFINE_VALARRAY_BIN_OP

        ///////////////////////////////////////////////////////////////////////////////
        // element-wise min of std::valarray
        template<typename Left, typename Right>
        struct min_assign<Left, Right, std_valarray_tag, std_valarray_tag>
          : std::binary_function<Left, Right, void>
        {
            void operator ()(Left &left, Right &right) const
            {
                BOOST_ASSERT(left.size() == right.size());
                for(std::size_t i = 0, size = left.size(); i != size; ++i)
                {
                    if(numeric::less(right[i], left[i]))
                    {
                        left[i] = right[i];
                    }
                }
            }
        };

        ///////////////////////////////////////////////////////////////////////////////
        // element-wise max of std::valarray
        template<typename Left, typename Right>
        struct max_assign<Left, Right, std_valarray_tag, std_valarray_tag>
          : std::binary_function<Left, Right, void>
        {
            void operator ()(Left &left, Right &right) const
            {
                BOOST_ASSERT(left.size() == right.size());
                for(std::size_t i = 0, size = left.size(); i != size; ++i)
                {
                    if(numeric::greater(right[i], left[i]))
                    {
                        left[i] = right[i];
                    }
                }
            }
        };

        // partial specialization of numeric::average<> for std::valarray.
        template<typename Left, typename Right, typename RightTag>
        struct average<Left, Right, std_valarray_tag, RightTag>
          : mpl::if_<
                are_integral<typename Left::value_type, Right>
              , divides<Left, double const>
              , divides<Left, Right>
            >::type
        {};

        // promote
        template<typename To, typename From>
        struct promote<To, From, std_valarray_tag, std_valarray_tag>
          : std::unary_function<From, To>
        {
            To operator ()(From &arr) const
            {
                typename remove_const<To>::type res(arr.size());
                for(std::size_t i = 0, size = arr.size(); i != size; ++i)
                {
                    res[i] = numeric::promote<typename To::value_type>(arr[i]);
                }
                return res;
            }
        };

        template<typename ToFrom>
        struct promote<ToFrom, ToFrom, std_valarray_tag, std_valarray_tag>
          : std::unary_function<ToFrom, ToFrom>
        {
            ToFrom &operator ()(ToFrom &tofrom) const
            {
                return tofrom;
            }
        };

        // for "promoting" a std::valarray<bool> to a bool, useful for
        // comparing 2 valarrays for equality:
        //   if(numeric::promote<bool>(a == b))
        template<typename From>
        struct promote<bool, From, void, std_valarray_tag>
          : std::unary_function<From, bool>
        {
            bool operator ()(From &arr) const
            {
                BOOST_MPL_ASSERT((is_same<bool, typename From::value_type>));
                for(std::size_t i = 0, size = arr.size(); i != size; ++i)
                {
                    if(!arr[i])
                    {
                        return false;
                    }
                }
                return true;
            }
        };

        template<typename From>
        struct promote<bool const, From, void, std_valarray_tag>
          : promote<bool, From, void, std_valarray_tag>
        {};

        ///////////////////////////////////////////////////////////////////////////////
        // functional::as_min
        template<typename T>
        struct as_min<T, std_valarray_tag>
            : std::unary_function<T, typename remove_const<T>::type>
        {
            typename remove_const<T>::type operator ()(T &arr) const
            {
                return 0 == arr.size()
                  ? T()
                  : T(numeric::as_min(arr[0]), arr.size());
            }
        };

        ///////////////////////////////////////////////////////////////////////////////
        // functional::as_max
        template<typename T>
        struct as_max<T, std_valarray_tag>
          : std::unary_function<T, typename remove_const<T>::type>
        {
            typename remove_const<T>::type operator ()(T &arr) const
            {
                return 0 == arr.size()
                  ? T()
                  : T(numeric::as_max(arr[0]), arr.size());
            }
        };

        ///////////////////////////////////////////////////////////////////////////////
        // functional::as_zero
        template<typename T>
        struct as_zero<T, std_valarray_tag>
          : std::unary_function<T, typename remove_const<T>::type>
        {
            typename remove_const<T>::type operator ()(T &arr) const
            {
                return 0 == arr.size()
                  ? T()
                  : T(numeric::as_zero(arr[0]), arr.size());
            }
        };

        ///////////////////////////////////////////////////////////////////////////////
        // functional::as_one
        template<typename T>
        struct as_one<T, std_valarray_tag>
          : std::unary_function<T, typename remove_const<T>::type>
        {
            typename remove_const<T>::type operator ()(T &arr) const
            {
                return 0 == arr.size()
                  ? T()
                  : T(numeric::as_one(arr[0]), arr.size());
            }
        };

    } // namespace functional

}} // namespace boost::numeric

#endif