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Fixed postfix increment for incrementable and single-pass iterator facade

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[SVN r23456]
This commit is contained in:
Dave Abrahams
2004-07-12 03:18:49 +00:00
parent 700efc2873
commit b6dee6532e
1 changed files with 39 additions and 20 deletions
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59
include/boost/detail/is_incrementable.hpp
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@ -19,14 +19,28 @@ namespace boost { namespace detail {
// This namespace ensures that ADL doesn't mess things up. // This namespace ensures that ADL doesn't mess things up.
namespace is_incrementable_ namespace is_incrementable_
{ {
// a type returned from operator++ when no increment is found in the
// type's own namespace
struct tag {}; struct tag {};
// any soaks up implicit conversions and makes the following // any soaks up implicit conversions and makes the following
// operator++ less-preferred than any other such operator which // operator++ less-preferred than any other such operator that
// might be found via ADL. // might be found via ADL.
struct any { template <class T> any(T const&); }; struct any { template <class T> any(T const&); };
tag operator++(any const&);
// This is a last-resort operator++ for when none other is found
tag operator++(any const&);
tag operator++(any const&,int);
# if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202)) \
|| BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
# define BOOST_comma(a,b) (a)
# else
// In case an operator++ is found that returns void, we'll use ++x,0
tag operator,(tag,int);
# define BOOST_comma(a,b) (a,b)
# endif
// two check overloads help us identify which operator++ was picked // two check overloads help us identify which operator++ was picked
char (& check(tag) )[2]; char (& check(tag) )[2];
@ -35,36 +49,41 @@ namespace is_incrementable_
template <class T> template <class T>
struct struct impl
# if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
impl
# else
is_incrementable
# endif
{ {
static typename remove_cv<T>::type& x; static typename remove_cv<T>::type& x;
BOOST_STATIC_CONSTANT( BOOST_STATIC_CONSTANT(
bool bool
, value = sizeof(is_incrementable_::check(++x)) == 1 , value = sizeof(is_incrementable_::check(BOOST_comma(++x,0))) == 1
); );
};
typedef mpl::bool_<( template <class T>
# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) struct postfix_impl
::boost::detail::is_incrementable_::is_incrementable<T>:: {
# endif static typename remove_cv<T>::type& x;
value)> type;
BOOST_STATIC_CONSTANT(
bool
, value = sizeof(is_incrementable_::check(BOOST_comma(x++,0))) == 1
);
}; };
} }
# if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) # undef BOOST_comma
template <class T> template <class T>
struct is_incrementable : is_incrementable_::impl<T> struct is_incrementable
: mpl::bool_< ::boost::detail::is_incrementable_::impl<T>::value>
{
};
template <class T>
struct is_postfix_incrementable
: mpl::bool_< ::boost::detail::is_incrementable_::postfix_impl<T>::value>
{ {
}; };
# else
using is_incrementable_::is_incrementable;
# endif
}} // namespace boost::detail }} // namespace boost::detail