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Added is_lvalue_iterator

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[SVN r20632]
This commit is contained in:
Dave Abrahams
2003-11-04 08:03:29 +00:00
parent 14134e4610
commit dfa751077a
3 changed files with 235 additions and 0 deletions
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148
include/boost/iterator/is_lvalue_iterator.hpp Executable file
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@ -0,0 +1,148 @@
// Copyright David Abrahams 2003. Use, modification and distribution is
// subject to 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 IS_LVALUE_ITERATOR_DWA2003112_HPP
# define IS_LVALUE_ITERATOR_DWA2003112_HPP
#include <boost/mpl/bool.hpp>
#include <boost/detail/iterator.hpp>
#include <boost/iterator.hpp>
// should be the last #include
#include <boost/type_traits/detail/bool_trait_def.hpp>
#include <boost/iterator/detail/config_def.hpp>
namespace boost {
namespace detail
{
#ifndef BOOST_NO_LVALUE_RETURN_DETECTION
// Calling lvalue_preserver( <expression>, 0 ) returns a reference
// to the expression's result if <expression> is an lvalue, or
// not_an_lvalue() otherwise.
struct not_an_lvalue {};
template <class T>
T& lvalue_preserver(T&, int);
template <class U>
not_an_lvalue lvalue_preserver(U const&, ...);
# define BOOST_LVALUE_PRESERVER(expr) lvalue_preserver(expr,0)
#else
# define BOOST_LVALUE_PRESERVER(expr) expr
#endif
struct any_conversion_eater
{
template <class T>
any_conversion_eater(T const&);
};
// Guts of is_lvalue_iterator. Value is the iterator's value_type
// and the result is computed in the nested rebind template.
template <class Value>
struct is_lvalue_iterator_impl
{
// Eat implicit conversions so we don't report true for things
// convertible to Value const&
struct conversion_eater
{
conversion_eater(Value&);
};
static char tester(conversion_eater, int);
static char (& tester(any_conversion_eater, ...) )[2];
template <class It>
struct rebind
{
static It& x;
BOOST_STATIC_CONSTANT(
bool
, value = (
sizeof(
is_lvalue_iterator_impl<Value>::tester(
BOOST_LVALUE_PRESERVER(*x), 0
)
) == 1
)
);
};
};
#undef BOOST_LVALUE_PRESERVER
//
// void specializations to handle std input and output iterators
//
template <>
struct is_lvalue_iterator_impl<void>
{
template <class It>
struct rebind : boost::mpl::false_
{};
};
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
template <>
struct is_lvalue_iterator_impl<const void>
{
template <class It>
struct rebind : boost::mpl::false_
{};
};
template <>
struct is_lvalue_iterator_impl<volatile void>
{
template <class It>
struct rebind : boost::mpl::false_
{};
};
template <>
struct is_lvalue_iterator_impl<const volatile void>
{
template <class It>
struct rebind : boost::mpl::false_
{};
};
#endif
//
// This level of dispatching is required for Borland. We might save
// an instantiation by removing it for others.
//
template <class It>
struct is_readable_lvalue_iterator_impl
: is_lvalue_iterator_impl<
BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<It>::value_type const
>::template rebind<It>
{};
template <class It>
struct is_writable_lvalue_iterator_impl
: is_lvalue_iterator_impl<
BOOST_DEDUCED_TYPENAME boost::detail::iterator_traits<It>::value_type
>::template rebind<It>
{};
} // namespace detail
// Define the trait with full mpl lambda capability and various broken
// compiler workarounds
BOOST_TT_AUX_BOOL_TRAIT_DEF1(
is_readable_lvalue_iterator,T,::boost::detail::is_readable_lvalue_iterator_impl<T>::value)
BOOST_TT_AUX_BOOL_TRAIT_DEF1(
is_writable_lvalue_iterator,T,::boost::detail::is_writable_lvalue_iterator_impl<T>::value)
} // namespace boost
#include <boost/iterator/detail/config_undef.hpp>
#endif // IS_LVALUE_ITERATOR_DWA2003112_HPP

1
test/Jamfile
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@ -19,6 +19,7 @@ test-suite iterator
[ run is_convertible_fail.cpp ]
# These tests should work for just about everything.
[ compile is_lvalue_iterator.cpp ]
[ run unit_tests.cpp ]
[ run concept_tests.cpp ]
[ run iterator_adaptor_cc.cpp ]

86
test/is_lvalue_iterator.cpp Executable file
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// Copyright David Abrahams 2003. Use, modification and distribution is
// subject to 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)
#include <deque>
#include <iterator>
#include <iostream>
#include <boost/static_assert.hpp>
#include <boost/noncopyable.hpp>
#include <boost/type_traits/broken_compiler_spec.hpp>
#include <boost/iterator/is_lvalue_iterator.hpp>
// Last, for BOOST_NO_LVALUE_RETURN_DETECTION
#include <boost/iterator/detail/config_def.hpp>
struct v
{
v();
~v();
};
BOOST_TT_BROKEN_COMPILER_SPEC(v)
struct value_iterator : boost::iterator<std::input_iterator_tag,v>
{
v operator*() const;
};
struct noncopyable_iterator : boost::iterator<std::forward_iterator_tag,boost::noncopyable>
{
boost::noncopyable const& operator*() const;
};
struct proxy_iterator : boost::iterator<std::output_iterator_tag,v>
{
#if BOOST_WORKAROUND(__GNUC__, == 2)
typedef boost::iterator<std::input_iterator_tag,v> base;
typedef base::iterator_category iterator_category;
typedef base::value_type value_type;
typedef base::difference_type difference_type;
typedef base::pointer pointer;
typedef base::reference reference;
#endif
struct proxy
{
operator v&() const;
proxy& operator=(v) const;
};
proxy operator*() const;
};
BOOST_TT_BROKEN_COMPILER_SPEC(proxy_iterator::proxy)
int main()
{
BOOST_STATIC_ASSERT(boost::is_readable_lvalue_iterator<v*>::value);
BOOST_STATIC_ASSERT(boost::is_readable_lvalue_iterator<v const*>::value);
BOOST_STATIC_ASSERT(boost::is_readable_lvalue_iterator<std::deque<v>::iterator>::value);
BOOST_STATIC_ASSERT(boost::is_readable_lvalue_iterator<std::deque<v>::const_iterator>::value);
BOOST_STATIC_ASSERT(!boost::is_readable_lvalue_iterator<std::back_insert_iterator<std::deque<v> > >::value);
BOOST_STATIC_ASSERT(!boost::is_readable_lvalue_iterator<std::ostream_iterator<v> >::value);
BOOST_STATIC_ASSERT(!boost::is_readable_lvalue_iterator<proxy_iterator>::value);
#ifndef BOOST_NO_LVALUE_RETURN_DETECTION
BOOST_STATIC_ASSERT(!boost::is_readable_lvalue_iterator<value_iterator>::value);
#endif
// Make sure inaccessible copy constructor doesn't prevent
// reference binding
BOOST_STATIC_ASSERT(boost::is_readable_lvalue_iterator<noncopyable_iterator>::value);
BOOST_STATIC_ASSERT(boost::is_writable_lvalue_iterator<v*>::value);
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<v const*>::value);
BOOST_STATIC_ASSERT(boost::is_writable_lvalue_iterator<std::deque<v>::iterator>::value);
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<std::deque<v>::const_iterator>::value);
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<std::back_insert_iterator<std::deque<v> > >::value);
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<std::ostream_iterator<v> >::value);
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<proxy_iterator>::value);
#ifndef BOOST_NO_LVALUE_RETURN_DETECTION
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<value_iterator>::value);
#endif
BOOST_STATIC_ASSERT(!boost::is_writable_lvalue_iterator<noncopyable_iterator>::value);
return 0;
}