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Refactor is_lvalue_iterator.hpp.

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Georgy Guminov
2025-01-25 11:51:32 +03:00
parent 8d080c6c58
commit bf4cce6114
1 changed files with 8 additions and 35 deletions
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43
include/boost/iterator/is_lvalue_iterator.hpp
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@ -6,7 +6,7 @@
#include <boost/detail/workaround.hpp>
#include <boost/iterator/detail/any_conversion_eater.hpp>
#include <boost/iterator/detail/type_traits/conjunction.hpp>
#include <boost/mpl/aux_/lambda_support.hpp>
#include <iterator>
@ -18,47 +18,20 @@ namespace iterators {
namespace detail
{
// 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&, ...);
// 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(typename std::add_lvalue_reference<Value>::type);
};
static char tester(conversion_eater, int);
static char (& tester(any_conversion_eater, ...) )[2];
{
template <class It>
using DerefT = decltype(*std::declval<It&>());
template <class It>
struct rebind
struct rebind : detail::conjunction<
std::is_convertible<DerefT<It>, typename std::add_lvalue_reference<Value>::type>
, std::is_lvalue_reference<DerefT<It>>
>::type
{
static It& x;
BOOST_STATIC_CONSTANT(
bool
, value = (
sizeof(
is_lvalue_iterator_impl<Value>::tester(
detail::lvalue_preserver(*x,0), 0
)
) == 1
)
);
};
};