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included rich_cons

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[SVN r11015]
This commit is contained in:
Jaakko Järvi
2001-09-04 10:44:37 +00:00
parent 5fb17f027f
commit c789016905
1 changed files with 20 additions and 1 deletions
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21
include/boost/tuple/detail/tuple_basic.hpp
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@ -22,6 +22,9 @@
// William Kempf, Vesa Karvonen, John Max Skaller, Ed Brey, Beman Davis,
// David Abrahams.
// Revision history:
// 2001 08 30 David Abrahams
// Added default constructor for cons<>.
// -----------------------------------------------------------------
#ifndef BOOST_TUPLE_BASIC_HPP
@ -79,6 +82,14 @@ struct default_arg {
// from all temporaries.
static typename boost::remove_cv<T>::type f() { return T(); }
};
// This is just to produce a more informative error message
// The code would fail in any case
template<class T, int N>
struct default_arg<T[N]> {
static T* f() {
return generate_error<T[N]>::arrays_are_not_valid_tuple_elements; }
};
template <class T>
struct default_arg<T&> {
@ -235,6 +246,12 @@ struct cons {
typename tuple_access_traits<tail_type>::const_type
get_tail() const { return tail; }
cons() : head(detail::tuples::default_arg<HT>::f()), tail() {}
// the argument for head is not strictly needed, but it prevents
// array type elements. This is good, since array type elements
// cannot be supported properly in any case (no assignment,
// copy works only if the tails are exactly the same type, ...)
cons(typename tuple_access_traits<head_type>::parameter_type h,
const tail_type& t)
: head (h), tail(t) {}
@ -302,7 +319,9 @@ struct cons<HT, null_type> {
get_head() const { return head; }
const null_type get_tail() const { return null_type(); }
cons() : head(detail::tuples::default_arg<HT>::f()) {}
cons(typename tuple_access_traits<head_type>::parameter_type h,
const null_type& = null_type())
: head (h) {}