I'm learning so much reading at the boost code, which is one of the reasons why I'm getting so excited. Please bear with my questions. The compiler appears to be having a problem with matching this operator== due to the return type, it can't find enable_if_interoperable<...>::type. Here's how aC++ expanded the macro BOOST_ITERATOR_FACADE_RELATION from your previous e-mail. template < class Derived1, class V1, class TC1, class R1, class D1 , class Derived2, class V2, class TC2, class R2, class D2 > inline typename detail::enable_if_interoperable< Derived1, Derived2 , typename mpl::apply2<detail::always_bool2,Derived1,Derived2>::type >::type operator ==( iterator_facade<Derived1, V1, TC1, R1, D1> const& lhs , iterator_facade<Derived2, V2, TC2, R2, D2> const& rhs) { typedef ::boost::static_assert_test< sizeof(::boost::STATIC_ASSERTION_FAILURE< (bool)( ( is_interoperable< Derived1, Derived2 >::value ) ) >)> boost_static_assert_typedef_622; return iterator_core_access::equal( static_cast<Derived1 const&>(lhs) , static_cast<Derived2 const&>(rhs) , is_convertible<Derived2,Derived1>() ); } enable_if_interoperable is declared as follows. It's empty, and since it inherits privately from enable_if, none of enable_if's members would be visible. Now where is the struct member "type"??? template <class Facade1, class Facade2, class Return > struct enable_if_interoperable: ::boost::iterators::enable_if< mpl::or_< is_convertible<Facade1, Facade2> , is_convertible<Facade2, Facade1> >, Return > { }; Thanks! -Jerry -----Original Message----- From: boost-bounces@lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of David Abrahams Sent: Wednesday, May 12, 2004 2:54 PM To: boost@lists.boost.org Subject: [boost] Re: Finding operator==(directory_iterator&,directory_iterator&) "DY, JERRY U (SBCSI)" <jd2419@sbc.com> writes:

In trying to compile the filesystem library, I'm getting an error that the compiler cannot find the operator== for the following function:

bool is_empty_directory( const fs::path & dir_path ) { return fs::directory_iterator(dir_path) == end_itr; }

aCC-C++-action

../../../bin/boost/libs/filesystem/build/libboost_filesystem.a/acc/debug

/operations_posix_windows.o Error 226: "../../../libs/filesystem/build/../src/operations_posix_windows.cpp", line 176 # No appropriate function found for call of 'operator =='.

class directory_iterator doesn't declare it, neither do ancestors iterator_facade and iterator_facade_types. Can't find free function for operator==(directory_iterator&, directory_iterator&), operator==(iterator_facade&, iterator_facade&), operator==(iterator_facade_types&, iterator_facade_types&) or any of its variants. Is it using the default compiler-generated operator== in directory_iterator?

The compiler is wrong. There is an operator== that takes two iterator_facade specializations in iterator_facade.hpp, generated by this line: BOOST_ITERATOR_FACADE_RELATION(==, return, equal) Try preprocessing the source if you need to see it. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost