operators.hpp

C++的一个好库。。。现在很流行

///////////////////////////////////////////////////////////////////////////////
//
//  binary_operator<TagT, T0, T1>
//
//      The binary_operator class implements most of the C++ binary
//      operators. Each specialization is basically a simple static eval
//      function plus a result_type typedef that determines the return
//      type of the eval function.
//
//      TagT is one of the binary operator tags above T0 and T1 are the
//      (arguments') data types involved in the operation.
//
//      Only the behavior of C/C++ built-in types are taken into account
//      in the specializations provided below. For user-defined types,
//      these specializations may still be used provided that the
//      operator overloads of such types adhere to the standard behavior
//      of built-in types.
//
//      T1 separate special_ops.hpp file implements more stl savvy
//      specializations. Other more specialized unary_operator
//      implementations may be defined by the client for specific
//      unary operator tags/data types.
//
//      All binary_operator except the logical_and_op and logical_or_op
//      have an eval static function that carries out the actual operation.
//      The logical_and_op and logical_or_op d are special because these
//      two operators are short-circuit evaluated.
//
///////////////////////////////////////////////////////////////////////////////
template <typename TagT, typename T0, typename T1>
struct binary_operator;

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs = rhs; }
};

//////////////////////////////////
template <typename T1>
struct binary_operator<index_op, nil_t, T1> {

    //  G++ eager template instantiation
    //  somehow requires this.
    typedef nil_t result_type;
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<index_op, T0*, T1> {

    typedef T0& result_type;
    static result_type eval(T0* ptr, T1 const& index)
    { return ptr[index]; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<index_op, T0* const, T1> {

    typedef T0& result_type;
    static result_type eval(T0* const ptr, T1 const& index)
    { return ptr[index]; }
};

//////////////////////////////////
template <typename T0, int N, typename T1>
struct binary_operator<index_op, T0[N], T1> {

    typedef T0& result_type;
    static result_type eval(T0* ptr, T1 const& index)
    { return ptr[index]; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<plus_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs += rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<minus_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs -= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<times_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs *= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<divide_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs /= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<mod_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs %= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<and_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs &= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<or_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs |= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<xor_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs ^= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<shift_l_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs <<= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<shift_r_assign_op, T0, T1> {

    typedef T0& result_type;
    static result_type eval(T0& lhs, T1 const& rhs)
    { return lhs >>= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<plus_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs + rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<minus_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs - rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<times_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs * rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<divide_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs / rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<mod_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs % rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<and_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs & rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<or_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs | rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<xor_op, T0, T1> {

    typedef typename higher_rank<T0, T1>::type const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs ^ rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<shift_l_op, T0, T1> {

    typedef T0 const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs << rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<shift_r_op, T0, T1> {

    typedef T0 const result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs >> rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<eq_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs == rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<not_eq_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs != rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<lt_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs < rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<lt_eq_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs <= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<gt_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs > rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<gt_eq_op, T0, T1> {

    typedef bool result_type;
    static result_type eval(T0 const& lhs, T1 const& rhs)
    { return lhs >= rhs; }
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<logical_and_op, T0, T1> {

    typedef bool result_type;
    //  no eval function, see comment above.
};

//////////////////////////////////
template <typename T0, typename T1>
struct binary_operator<logical_or_op, T0, T1> {

    typedef bool result_type;
    //  no eval function, see comment above.
};

///////////////////////////////////////////////////////////////////////////////
//
//  negative lazy operator (prefix -)
//
///////////////////////////////////////////////////////////////////////////////
struct negative_op {

    template <typename T0>
    struct result {

        typedef typename unary_operator<negative_op, T0>::result_type type;
    };

    template <typename T0>
    typename unary_operator<negative_op, T0>::result_type
    operator()(T0& _0) const
    { return unary_operator<negative_op, T0>::eval(_0); }
};

//////////////////////////////////
template <typename BaseT>
inline typename impl::make_unary<negative_op, BaseT>::type
operator-(actor<BaseT> const& _0)
{
    return impl::make_unary<negative_op, BaseT>::construct(_0);
}

///////////////////////////////////////////////////////////////////////////////
//
//  positive lazy operator (prefix +)
//
///////////////////////////////////////////////////////////////////////////////
struct positive_op {

    template <typename T0>
    struct result {

        typedef typename unary_operator<positive_op, T0>::result_type type;
    };

    template <typename T0>
    typename unary_operator<positive_op, T0>::result_type
    operator()(T0& _0) const
    { return unary_operator<positive_op, T0>::eval(_0); }
};

//////////////////////////////////
template <typename BaseT>
inline typename impl::make_unary<positive_op, BaseT>::type
operator+(actor<BaseT> const& _0)
{
    return impl::make_unary<positive_op, BaseT>::construct(_0);
}

///////////////////////////////////////////////////////////////////////////////
//
//  logical not lazy operator (prefix !)
//
///////////////////////////////////////////////////////////////////////////////
struct logical_not_op {

    template <typename T0>
    struct result {

        typedef typename unary_operator<logical_not_op, T0>::result_type type;
    };

    template <typename T0>
    typename unary_operator<logical_not_op, T0>::result_type
    operator()(T0& _0) const
    { return unary_operator<logical_not_op, T0>::eval(_0); }
};

//////////////////////////////////
template <typename BaseT>
inline typename impl::make_unary<logical_not_op, BaseT>::type
operator!(actor<BaseT> const& _0)
{
    return impl::make_unary<logical_not_op, BaseT>::construct(_0);
}