David Abrahams wrote:
I'm having trouble getting make_filter_iterator and bind to work together nicely:
------------------------------------------------------------------------------- boost::function<bool (const node_type&)> is_constraint; is_constraint = boost::bind(&node_type::IsConstraint, _1);
boost::make_filter_iterator(is_constraint, ab.begin(), ab.end()); // ERROR: does not compile boost::make_filter_iterator(boost::bind(&node_type::IsConstraint, _1), ab.begin(), ab.end()); // compiles -------------------------------------------------------------------------------
Note that ab.begin()/ab.end() return iterators to containers of shared pointers. See below for compiler errors.
It's actually not bind, but function. Bind contains magic that treats shared_ptr<T> and T& the same way, but for function to take advantage of that magic, you need to make sure its argument type is shared_ptr<T>, not T&:
boost::function<bool (shared_ptr<node_type const>)> is_constraint = boost::bind(&node_type::IsConstraint, _1);
boost::make_filter_iterator(is_constraint, ab.begin(), ab.end());
Thanks, that works like a charm. Unfortunately, dereferencing the created iterator gives more trouble: boost::function<bool (shared_ptr<node_type const>)> is_constraint = boost::bind(&node_type::IsConstraint, _1); typedef boost::filter_iterator<boost::function<bool (shared_ptr<node_type const>)>, articulated_model_type::node_df_traversal_iterator> joint_node_iterator; joint_node_iterator jointnode = boost::make_filter_iterator(is_constraint, ab.begin(), ab.end()); std::cout << jointnode->Model(); ///< this line fails to compile There seems to be a problem with const-ness (see below). Thanks again. --nico ------------------------------------------------------------------------------ d:\dev\boost_1_33_1\boost\iterator\iterator_adaptor.hpp(307) : error C2440: 'return' : cannot convert from 'Hybrid::Graph<node_traits>::const_node_ptr' to 'boost::iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Difference>::reference' with [ node_traits=Hybrid::ArticulatedModelNodeTraits<MyTypes> ] and [ Derived=boost::filter_iterator<boost::function<bool (boost::shared_ptr<const Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_type>)>,Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>, Value=boost::iterator_value<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type, CategoryOrTraversal=boost::mpl::identity<boost::forward_traversal_tag>::type, Reference=boost::iterator_reference<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type, Difference=boost::iterator_difference<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type ] A reference that is not to 'const' cannot be bound to a non-lvalue d:\dev\boost_1_33_1\boost\iterator\iterator_adaptor.hpp(307) : while compiling class-template member function 'boost::iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Difference>::reference boost::iterator_adaptor<Derived,Base,boost::use_default,Traversal>::dereference(void) const' with [ Derived=boost::filter_iterator<boost::function<bool (boost::shared_ptr<const Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_type>)>,Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>, Value=boost::iterator_value<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type, CategoryOrTraversal=boost::mpl::identity<boost::forward_traversal_tag>::type, Reference=boost::iterator_reference<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type, Difference=boost::iterator_difference<Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>::type, Base=Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator, Traversal=boost::mpl::if_<boost::is_convertible<boost::mpl::identity<boost::forward_traversal_tag>::type,boost::random_access_traversal_tag>,boost::bidirectional_traversal_tag,boost::use_default>::type ] d:\dev\boost_1_33_1\boost\iterator\filter_iterator.hpp(46) : see reference to class template instantiation 'boost::iterator_adaptor<Derived,Base,Value,Traversal>' being compiled with [ Derived=boost::filter_iterator<boost::function<bool (boost::shared_ptr<const Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_type>)>,Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator>, Base=Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_ iterator, Value=boost::use_default, Traversal=boost::mpl::if_<boost::is_convertible<boost::mpl::identity<boost::forward_traversal_tag>::type,boost::random_access_traversal_tag>,boost::bidirectional_traversal_tag,boost::use_default>::type ] d:\dev\Hybrid\Tests\Graph\main.cpp(398) : see reference to class template instantiation 'boost::filter_iterator<Predicate,Iterator>' being compiled with [ Predicate=boost::function<bool (boost::shared_ptr<const Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_type>)>, Iterator=Hybrid::Graph<Hybrid::ArticulatedModelNodeTraits<MyTypes>>::node_df_traversal_iterator ] -- nico galoppo von borries @ address: 105 creel st., chapel hill comp. graphics phd. student @ north carolina, 27516 USA UNC, chapel hill @ phone: +1 (919) 962-1898 (office) @ +1 (919) 942-7609 (home) @ email: nico at cs dot unc dot edu @ homepage: http://www.cs.unc.edu/~nico --- debian linux :: vim powered