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Reimplement boost::tuples::element and boost::tuples::get to make better use of memoization. Fixes #2130

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[SVN r62683]
This commit is contained in:
Steven Watanabe
2010-06-09 18:28:16 +00:00
parent 052b3db77f
commit 1b07c1a2d4
1 changed files with 37 additions and 101 deletions
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138
include/boost/tuple/detail/tuple_basic.hpp
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@ -86,45 +86,28 @@ namespace detail {
template<class T>
class generate_error;
// - cons getters --------------------------------------------------------
// called: get_class<N>::get<RETURN_TYPE>(aTuple)
template< int N >
struct get_class {
template<class RET, class HT, class TT >
inline static RET get(const cons<HT, TT>& t)
{
#if BOOST_WORKAROUND(__IBMCPP__,==600)
// vacpp 6.0 is not very consistent regarding the member template keyword
// Here it generates an error when the template keyword is used.
return get_class<N-1>::get<RET>(t.tail);
#else
return get_class<N-1>::BOOST_NESTED_TEMPLATE get<RET>(t.tail);
#endif
}
template<class RET, class HT, class TT >
inline static RET get(cons<HT, TT>& t)
{
#if BOOST_WORKAROUND(__IBMCPP__,==600)
return get_class<N-1>::get<RET>(t.tail);
#else
return get_class<N-1>::BOOST_NESTED_TEMPLATE get<RET>(t.tail);
#endif
}
template<int N>
struct drop_front {
template<class Tuple>
struct apply {
typedef BOOST_DEDUCED_TYPENAME drop_front<N-1>::BOOST_NESTED_TEMPLATE
apply<Tuple> next;
typedef BOOST_DEDUCED_TYPENAME next::type::tail_type type;
static const type& call(const Tuple& tup) {
return next::call(tup).tail;
}
};
};
template<>
struct get_class<0> {
template<class RET, class HT, class TT>
inline static RET get(const cons<HT, TT>& t)
{
return t.head;
}
template<class RET, class HT, class TT>
inline static RET get(cons<HT, TT>& t)
{
return t.head;
}
struct drop_front<0> {
template<class Tuple>
struct apply {
typedef Tuple type;
static const type& call(const Tuple& tup) {
return tup;
}
};
};
} // end of namespace detail
@ -140,41 +123,23 @@ struct get_class<0> {
template<int N, class T>
struct element
{
private:
typedef typename T::tail_type Next;
public:
typedef typename element<N-1, Next>::type type;
};
template<class T>
struct element<0,T>
{
typedef typename T::head_type type;
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<T>::type::head_type type;
};
template<int N, class T>
struct element<N, const T>
{
private:
typedef typename T::tail_type Next;
typedef typename element<N-1, Next>::type unqualified_type;
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<T>::type::head_type unqualified_type;
public:
#if BOOST_WORKAROUND(__BORLANDC__,<0x600)
typedef const unqualified_type type;
#else
typedef typename boost::add_const<unqualified_type>::type type;
#endif
};
template<class T>
struct element<0,const T>
{
#if BOOST_WORKAROUND(__BORLANDC__,<0x600)
typedef const typename T::head_type type;
#else
typedef typename boost::add_const<typename T::head_type>::type type;
typedef BOOST_DEDUCED_TYPENAME boost::add_const<unqualified_type>::type type;
#endif
};
#else // def BOOST_NO_CV_SPECIALIZATIONS
namespace detail {
@ -182,31 +147,16 @@ namespace detail {
template<int N, class T, bool IsConst>
struct element_impl
{
private:
typedef typename T::tail_type Next;
public:
typedef typename element_impl<N-1, Next, IsConst>::type type;
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<T>::type::head_type type;
};
template<int N, class T>
struct element_impl<N, T, true /* IsConst */>
{
private:
typedef typename T::tail_type Next;
public:
typedef const typename element_impl<N-1, Next, true>::type type;
};
template<class T>
struct element_impl<0, T, false /* IsConst */>
{
typedef typename T::head_type type;
};
template<class T>
struct element_impl<0, T, true /* IsConst */>
{
typedef const typename T::head_type type;
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<T>::type::head_type unqualified_type;
typedef const unqualified_type type;
};
} // end of namespace detail
@ -258,17 +208,10 @@ inline typename access_traits<
typename element<N, cons<HT, TT> >::type
>::non_const_type
get(cons<HT, TT>& c BOOST_APPEND_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) {
#if BOOST_WORKAROUND(__IBMCPP__,==600 )
return detail::get_class<N>::
#else
return detail::get_class<N>::BOOST_NESTED_TEMPLATE
#endif
get<
typename access_traits<
typename element<N, cons<HT, TT> >::type
>::non_const_type,
HT,TT
>(c);
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<cons<HT, TT> > impl;
typedef BOOST_DEDUCED_TYPENAME impl::type cons_element;
return const_cast<cons_element&>(impl::call(c)).head;
}
// get function for const cons-lists, returns a const reference to
@ -279,17 +222,10 @@ inline typename access_traits<
typename element<N, cons<HT, TT> >::type
>::const_type
get(const cons<HT, TT>& c BOOST_APPEND_EXPLICIT_TEMPLATE_NON_TYPE(int, N)) {
#if BOOST_WORKAROUND(__IBMCPP__,==600)
return detail::get_class<N>::
#else
return detail::get_class<N>::BOOST_NESTED_TEMPLATE
#endif
get<
typename access_traits<
typename element<N, cons<HT, TT> >::type
>::const_type,
HT,TT
>(c);
typedef BOOST_DEDUCED_TYPENAME detail::drop_front<N>::BOOST_NESTED_TEMPLATE
apply<cons<HT, TT> > impl;
typedef BOOST_DEDUCED_TYPENAME impl::type cons_element;
return impl::call(c).head;
}
// -- the cons template --------------------------------------------------