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Enhance is_convertible.h with boost::mpl rather than handmade enum { value = }

This commit is contained in:
Mael Rouxel-Labbé 2020-06-21 12:03:53 +02:00
parent 2d49f7d702
commit ad803b82b5
1 changed files with 48 additions and 36 deletions
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70
STL_Extension/include/CGAL/is_iterator.h
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@ -17,12 +17,14 @@
#ifndef CGAL_IS_ITERATOR_H
#define CGAL_IS_ITERATOR_H
#include <iterator>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/mpl/has_xxx.hpp>
#include <boost/mpl/logical.hpp>
#include <iterator>
namespace CGAL {
namespace internal {
@ -35,42 +37,52 @@ BOOST_MPL_HAS_XXX_TRAIT_DEF(reference)
//We request the type to be either a pointer or to
//provide all 5 nested types provided by iterator_traits
template <class T> struct is_iterator_ {
enum { value =
( has_iterator_category<T>::value &&
has_value_type<T>::value &&
has_difference_type<T>::value &&
has_pointer<T>::value &&
has_reference<T>::value
)
|| boost::is_pointer<T>::value };
};
template <class T>
struct is_iterator_
: public boost::mpl::or_<
boost::mpl::and_<
has_iterator_category<T>,
has_value_type<T>,
has_difference_type<T>,
has_pointer<T>,
has_reference<T> >,
boost::is_pointer<T> >
{ };
template <class T, class U, bool = is_iterator_<T>::value>
struct is_iterator_type_ {
enum { value=false };
};
template <class T,class U> struct is_iterator_type_<T,U,true> :
//boost::is_base_of<U,typename std::iterator_traits<T>::iterator_category>
struct is_iterator_type_
: public boost::mpl::false_
{ };
template <class T,class U>
struct is_iterator_type_<T, U, true>
: public //boost::is_base_of<U,typename std::iterator_traits<T>::iterator_category>
boost::is_convertible<typename std::iterator_traits<T>::iterator_category, U>
{ };
}
} // namespace internal
// NOTE: we don't want the real std::decay or functions are included
template <class T> struct is_iterator :
internal::is_iterator_<typename boost::remove_cv<typename boost::remove_reference<T>::type>::type> {};
template <class T,class Tag> struct is_iterator_type :
internal::is_iterator_type_<typename boost::remove_cv<typename boost::remove_reference<T>::type>::type,Tag> {};
template <class T,class U,bool=is_iterator<T>::value> struct is_iterator_to {
enum { value=false };
};
template <class T,class U> struct is_iterator_to<T,U,true> :
boost::is_convertible<typename std::iterator_traits<T>::value_type,U>
template <class T>
struct is_iterator
: public internal::is_iterator_<typename boost::remove_cv<typename boost::remove_reference<T>::type>::type>
{ };
}
template <class T, class Tag>
struct is_iterator_type
: public internal::is_iterator_type_<typename boost::remove_cv<typename boost::remove_reference<T>::type>::type, Tag>
{ };
template <class T, class U, bool = is_iterator<T>::value>
struct is_iterator_to
: public boost::mpl::false_
{ };
template <class T, class U>
struct is_iterator_to<T, U, true>
: public boost::is_convertible<typename std::iterator_traits<T>::value_type, U>
{ };
} // namespace CGAL
#endif // CGAL_IS_ITERATOR_H