text: ///////////////////////////////////////////////////////////////////////////////
  /// \file vector.hpp
  ///
  //  Copyright 2005 Eric Niebler. Distributed under the Boost
  //  Software License, Version 1.0. (See accompanying file
  //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  
  #ifndef BOOST_NUMERIC_FUNCTIONAL_VECTOR_HPP_EAN_12_12_2005
  #define BOOST_NUMERIC_FUNCTIONAL_VECTOR_HPP_EAN_12_12_2005
  
  #ifdef BOOST_NUMERIC_FUNCTIONAL_HPP_INCLUDED
  # error Include this file before boost/accumulators/numeric/functional.hpp
  #endif
  
  #include <vector>
  #include <functional>
  #include <boost/assert.hpp>
  #include <boost/mpl/and.hpp>
  #include <boost/mpl/not.hpp>
  #include <boost/utility/enable_if.hpp>
  #include <boost/type_traits/is_same.hpp>
  #include <boost/type_traits/is_scalar.hpp>
  #include <boost/type_traits/remove_const.hpp>
  #include <boost/typeof/std/vector.hpp>
  #include <boost/accumulators/numeric/functional_fwd.hpp>
  
  namespace boost { namespace numeric
  {
      namespace operators
      {
          namespace acc_detail
          {
              template<typename Fun>
              struct make_vector
              {
                  typedef std::vector<typename Fun::result_type> type;
              };
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> / Right where Right is a scalar.
          template<typename Left, typename Right>
          typename lazy_enable_if<
              is_scalar<Right>
            , acc_detail::make_vector<functional::divides<Left, Right> >
          >::type
          operator /(std::vector<Left> const &left, Right const &right)
          {
              typedef typename functional::divides<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::divides(left[i], right);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> / vector<Right>.
          template<typename Left, typename Right>
          std::vector<typename functional::divides<Left, Right>::result_type>
          operator /(std::vector<Left> const &left, std::vector<Right> const &right)
          {
              typedef typename functional::divides<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::divides(left[i], right[i]);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> * Right where Right is a scalar.
          template<typename Left, typename Right>
          typename lazy_enable_if<
              is_scalar<Right>
            , acc_detail::make_vector<functional::multiplies<Left, Right> >
          >::type
          operator *(std::vector<Left> const &left, Right const &right)
          {
              typedef typename functional::multiplies<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::multiplies(left[i], right);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle Left * vector<Right> where Left is a scalar.
          template<typename Left, typename Right>
          typename lazy_enable_if<
              is_scalar<Left>
            , acc_detail::make_vector<functional::multiplies<Left, Right> >
          >::type
          operator *(Left const &left, std::vector<Right> const &right)
          {
              typedef typename functional::multiplies<Left, Right>::result_type value_type;
              std::vector<value_type> result(right.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::multiplies(left, right[i]);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> * vector<Right>
          template<typename Left, typename Right>
          std::vector<typename functional::multiplies<Left, Right>::result_type>
          operator *(std::vector<Left> const &left, std::vector<Right> const &right)
          {
              typedef typename functional::multiplies<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::multiplies(left[i], right[i]);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> + vector<Right>
          template<typename Left, typename Right>
          std::vector<typename functional::plus<Left, Right>::result_type>
          operator +(std::vector<Left> const &left, std::vector<Right> const &right)
          {
              typedef typename functional::plus<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::plus(left[i], right[i]);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> - vector<Right>
          template<typename Left, typename Right>
          std::vector<typename functional::minus<Left, Right>::result_type>
          operator -(std::vector<Left> const &left, std::vector<Right> const &right)
          {
              typedef typename functional::minus<Left, Right>::result_type value_type;
              std::vector<value_type> result(left.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::minus(left[i], right[i]);
              }
              return result;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle vector<Left> += vector<Left>
          template<typename Left>
          std::vector<Left> &
          operator +=(std::vector<Left> &left, std::vector<Left> const &right)
          {
              BOOST_ASSERT(left.size() == right.size());
              for(std::size_t i = 0, size = left.size(); i != size; ++i)
              {
                  numeric::plus_assign(left[i], right[i]);
              }
              return left;
          }
  
          ///////////////////////////////////////////////////////////////////////////////
          // Handle -vector<Arg>
          template<typename Arg>
          std::vector<typename functional::unary_minus<Arg>::result_type>
          operator -(std::vector<Arg> const &arg)
          {
              typedef typename functional::unary_minus<Arg>::result_type value_type;
              std::vector<value_type> result(arg.size());
              for(std::size_t i = 0, size = result.size(); i != size; ++i)
              {
                  result[i] = numeric::unary_minus(arg[i]);
              }
              return result;
          }
      }
  
      namespace functional
      {
          struct std_vector_tag;
  
          template<typename T, typename Al>
          struct tag<std::vector<T, Al> >
          {
              typedef std_vector_tag type;
          };
  
          ///////////////////////////////////////////////////////////////////////////////
          // element-wise min of std::vector
          template<typename Left, typename Right>
          struct min_assign<Left, Right, std_vector_tag, std_vector_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::vector
          template<typename Left, typename Right>
          struct max_assign<Left, Right, std_vector_tag, std_vector_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 for std::vector.
          template<typename Left, typename Right>
          struct average<Left, Right, std_vector_tag, void>
            : 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_vector_tag, std_vector_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_vector_tag, std_vector_tag>
            : std::unary_function<ToFrom, ToFrom>
          {
              ToFrom &operator ()(ToFrom &tofrom) const
              {
                  return tofrom;
              }
          };
  
          ///////////////////////////////////////////////////////////////////////////////
          // functional::as_min
          template<typename T>
          struct as_min<T, std_vector_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(arr.size(), numeric::as_min(arr[0]));
              }
          };
  
          ///////////////////////////////////////////////////////////////////////////////
          // functional::as_max
          template<typename T>
          struct as_max<T, std_vector_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(arr.size(), numeric::as_max(arr[0]));
              }
          };
  
          ///////////////////////////////////////////////////////////////////////////////
          // functional::as_zero
          template<typename T>
          struct as_zero<T, std_vector_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(arr.size(), numeric::as_zero(arr[0]));
              }
          };
  
          ///////////////////////////////////////////////////////////////////////////////
          // functional::as_one
          template<typename T>
          struct as_one<T, std_vector_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(arr.size(), numeric::as_one(arr[0]));
              }
          };
  
      } // namespace functional
  
  }} // namespace boost::numeric
  
  #endif
  
  