November 2008 - Boost - lists.boost.org

Excellent factory style design pattern implementation
by Michael Goldshteyn 07 Dec '08

07 Dec '08

I thought that everyone might be interested in the following which basically creates a Boost-Centric Factory-Pattern Implementation, including: Factory Abstract Factory Prototype Here is a link to the article and the actual code: http://arcticinteractive.com/2008/10/06/boost-centric-factory-pattern-imple… I was very impressed with the work and am almost wondering if this is ready for a review and inclusion into Boost proper. Thanks, Michael Goldshteyn

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A design for geometric objects
by Mathias Gaunard 07 Dec '08

07 Dec '08

The past discussions on geometric libraries focused on how to define points. What matters even more however is how geometric objects are designed. There is a natural subtyping relationship between geometric objects. Deriving a square from a rectangle is usually frowned upon in OOP, because it can easily break the Liskov Substitution Principle if the objects are mutable. Making them immutable, however, solves the issue altogether. Morever, by using static subtyping, e.g. with concepts, we have multiple dispatch for free and don't pay any performance overhead, making such a design much better than with OOP. Concepts being non-intrusive, a mutable object may well be implemented but the concept can be a read-only view. Note that while I'm talking about concepts, I don't necessarily mean C++0x concepts, it could also be an alternative system. I would like to be able to write generic algorithms for geometric objects. Say I write an algorithm for any simple polygon. That algorithm should work with any simple quadrilateral, simple triangle, a rectangle, etc. Then I rewrite the same algorithm for convex polygons. So non-convex simple polygons should invoke the old algorithm, and convex ones the new one. So a system to find best matches is required. If we consider the subtyping graph for rectangle (which is not the most complex object, but certainly is complex enough to expose a complex graph), here is what we get: Rectangle < Right-angled Trapezium < Trapezium < ConvexQuadrilateral < Parallelogram < Trapezium ConvexQuadrilateral < SimpleQuadrilateral < Quadrilateral < Polygon < ConvexPolygon < SimplePolygon SimplePolygon < InsideSimplePolygonalLine SimplePolygon < Polygon Polygon < PolygonHole < Curve Polygon < InsidePolygonalLine InsideSimplePolygonalLine < InsideSimpleClosedCurve InsideSimplePolygonalLine < InsidePolygonalLine < InsideClosedCurve InsideSimpleClosedCurve < InsideClosedCurve < Curve SimpleClosedCurve < ClosedCurve < Curve InsideSimpleClosedCurve -> SimpleClosedCurve (composition thingy) InsideClosedCurve -> ClosedCurve (composition thingy) Curve < Object For clarification, a curve is here defined as the image of a continuous map from a real interval to the space. That is to say any set of points that is "connected". A simple curve is a curve that doesn't cross itself (just like simple polygons), which means the the map is injective, and a closed curve is a curve where the application comes from a closed interval and where the image is the same on both boundaries. A closed simple curve is a closed curve that is injective but for the boundaries. InsideClosedCurve defines the space with is "inside" a closed curve, which could also be defined by another map (known as a space-filling curve, but they are harder to manipulate, at least for polygons). A Polygon is an InsideClosedCurve with the closed curve being line segments within a plan. A PolygonHole is a Polygon which may have holes themselves defined by closed curves. An Object is a possibly (likely, even) infinite set of points in space. There is quite a complexity and redundancy here. It would be nice if it was possible to enhance that somehow. And that graph probably isn't fully complete, for example "right-angled" should probably be made separate propriety from trapezium. Also there should probably be Polytope somewhere. And PolygonHole lacks specializations too. The worse is the Inside thingies. I suppose having template concepts of some kind could help. Therefore I am wondering if there is any way to make the design simpler and more elegant. Indeed, such a design seems hard to maintain, it doesn't scale so well, and if I want to include something in there I probably have to modify other concepts as well. A geometric object is really just a set of proprieties. Working with meta-functions like is_quadrilateral, is_convex or is_simple seems like less work and verbosity. But how can such a system provide subtyping and best matches? Any comments and ideas are welcome.

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[interprocess] default constructors
by Jan Stetka 06 Dec '08

06 Dec '08

Hi, Is there any reason why named_mutex and managed_shared_memory don't have a default constructor?

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n2427 atomic implementation?
by vicente.botet 05 Dec '08

05 Dec '08

Hi, Can the N2427 - C++ Atomic Types and Operations be implemented without the help of the compiler? Do some one have a partial implementation? Vicente

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[Serialization] this seems wrong
by Kenny Riddile 05 Dec '08

05 Dec '08

I'm somewhat inexperienced with boost serialization, so forgive me if I'm just missing something. I have a few simple classes that are all serializable. In each class's header, I have BOOST_CLASS_EXPORT( ClassName ) right after the class declaration. All of these classes are header-only, so there is no cpp. All of these classes are very similar, so the statement above is often on the same line of the file (line 21 in this case). When I include all of these headers in a single source file, I get errors like this: 1>Win32WindowImpl.cpp 1>c:\subversion\trunk\vfx\platform\include\messages\minimized.hpp(21) : error C2371: 'vfx::platform::`anonymous-namespace'::boost_serialization_guid_initializer_21' : redefinition; different basic types 1> c:\subversion\trunk\vfx\platform\include\messages\close.hpp(21) : see declaration of 'vfx::platform::`anonymous-namespace'::boost_serialization_guid_initializer_21' 1>c:\subversion\trunk\vfx\platform\include\messages\restored.hpp(21) : error C2371: 'vfx::platform::`anonymous-namespace'::boost_serialization_guid_initializer_21' : redefinition; different basic types 1> c:\subversion\trunk\vfx\platform\include\messages\close.hpp(21) : see declaration of 'vfx::platform::`anonymous-namespace'::boost_serialization_guid_initializer_21' I walked down into the BOOST_CLASS_EXPORT macro and saw that the BOOST_CLASS_EXPORT_GUID macro appends the line number (notice the 21's in the above compiler output) to what it generates. Thinking to myself, "this will never work", I simply went and added empty lines to the header files so that the BOOST_CLASS_EXPORT( ClassName ) was on a different line in each and everything compiled. Am I missing something? Is this fixed in 1.37 (I'm currently forced to use 1.36). If I wanted white-space to matter, I would be writing python :)

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[MPL] new run-time algorithm: for_all
by George van Venrooij 05 Dec '08

05 Dec '08

Hello everyone, I recently created a MPL-based run-time algorithm named "for_all" which you can find at the following location: http://tinyurl.com/5a9d9d It is based on the "for_each" algorithm. The main difference is that it traverses a sequence of sequences and constructs new sequences that are then passed to a functor. Read the article for more information. I found it to be very useful in several cases, so I wanted to share it with the community. If you have any comments or spot any problems, please let me know. Regards, George ------------------------------------------------------------------------ George van Venrooij Organic Vectory http://www.organicvectory.com

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Breaking existing libraries
by Tomas Puverle 05 Dec '08

05 Dec '08

You may or may not have noticed a thread I started on boost.users about the breaking changes to Boost.Range. Here’s a short summary: We are currently (firmwide) using boost 1.33.1. I am in the process of trying to migrate and test some of our apps with boost 1.37. In 1.35 there was a breaking change to Boost.Range with respect to how singular ranges behave. This brings up several issues: 1) The breakage was silent. The interface stayed the same but the behavior changed, and drastically so. 2) No communation: While I don’t usually post to boost.devel/boost.user, I and my colleagues still read it. Nobody recalls any mention of this on the list. Searching gmane brings up nothing, either. 3) No documentation on the boost website. As far as I can see, this change was introduced in 1.35 this March. On http://www.boost.org/users/news/version_1_35_0, there is no mention of a breaking change to Boost.Range. 4) The new Boost.Range behaves differently in debug and release builds. The public function is_singular() always returns false in release builds even when it would return true in debug builds. Apart from the fact that this change breaks a lot of our code and obsoletes several useful (necessary?) idioms, the manner in which it happened is far below the standards that one has come to expect from boost. At the moment, I have to say I don’t have a good answer to how to fix our code. However, I would at least like to try to make sure this kind of silent breakage doesn’t happen again. Tom

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[graph] 'short' in bundled property throws boost::bad_any_cast
by remi.chateauneu＠gmx.de 05 Dec '08

05 Dec '08

Hi, I have a graph with a bundled property whose one of the members is a 'short'. When calling read_graphml, it throws an exception: terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::bad_any_cast> >' what(): boost::bad_any_cast: failed conversion using boost::any_cast Same problem with 'unsigned short'. With 'int' and 'long', it works.

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[interprocess] map of vectors
by Jan Stetka 02 Dec '08

02 Dec '08

Hi, Is something like this likely to work? typedef interprocess::vector<int, ShmemAllocator> MyVector typedef std::pair<const long, MyVector> ValueType; typedef allocator<ValueType, managed_shared_memory::segment_manager> ShmemAllocator; typedef interprocess::map<long, MyVector, std::less<long>, ShmemAllocator> MyMap;

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[graph] Bundled properties, listS, listS, write_graphml
by remi.chateauneu＠gmx.de 02 Dec '08

02 Dec '08

Hi, I try to use boost::graph with two bundled properties, listS for vertices and edges, and serialize with write_graphml, and it does not compile: Boost 1.35 and 1.36, Windows Visual C++ 8.0 Here are the most important details of the code: class Host { int idx ; }; class SocketPair { int xxx ; }; typedef boost::adjacency_list< boost::listS, /// Needs stability of iterators. boost::listS, /// Needs stability of iterators. boost::directedS, Host, SocketPair > Graph; Graph gblGrf ; boost::dynamic_properties tmpDP ; boost::write_graphml( std::ofstream("xxx.xml"), boost::vertex_index_map( boost::get( &Host::idx,_gblGrf ) ), gblGrf, tmpDP ); Here is the beginning of the compile errors. Any idea, please ?? Thanks in advance 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : error C2039: 'vertex_descriptor' : is not a member of 'boost::bgl_named_params<T,Tag,Base>' 1> with 1> [ 1> T=boost::bundle_property_map<boost::adjacency_list<boost::listS,boost::l istS,boost::directedS,Host,SocketPair>,void *,Host,int>, 1> Tag=boost::vertex_index_t, 1> Base=boost::no_property 1> ] 1> c:\program files\boost\boost_1_36_0\boost\graph\graphml.hpp(225) : see reference to class template instantiation 'boost::graph_traits<G>' being compiled 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1> i:\remi\graph\graph\graph.cpp(435) : see reference to function template instantiation 'void boost::write_graphml<boost::bgl_named_params<T,Tag,Base>,Netstat::Graph> (std::ostream &,const Graph &,VertexIndexMap,const boost::dynamic_properties &,bool)' being compiled 1> with 1> [ 1> T=boost::bundle_property_map<boost::adjacency_list<boost::listS,boost::l istS,boost::directedS,Host,SocketPair>,void *,Host,int>, 1> Tag=boost::vertex_index_t, 1> Base=boost::no_property, 1> Graph=boost::bgl_named_params<boost::bundle_property_map<boost::adjacenc y_list<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property>, 1> VertexIndexMap=Netstat::Graph 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : error C2146: syntax error : missing ';' before identifier 'vertex_descriptor' 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : error C2602: 'boost::graph_traits<G>::vertex_descriptor' is not a member of a base class of 'boost::graph_traits<G>' 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1> c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : see declaration of 'boost::graph_traits<G>::vertex_descriptor' 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(26) : error C2868: 'boost::graph_traits<G>::vertex_descriptor' : illegal syntax for using-declaration; expected qualified-name 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : error C2039: 'edge_descriptor' : is not a member of 'boost::bgl_named_params<T,Tag,Base>' 1> with 1> [ 1> T=boost::bundle_property_map<boost::adjacency_list<boost::listS,boost::l istS,boost::directedS,Host,SocketPair>,void *,Host,int>, 1> Tag=boost::vertex_index_t, 1> Base=boost::no_property 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : error C2146: syntax error : missing ';' before identifier 'edge_descriptor' 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : error C2602: 'boost::graph_traits<G>::edge_descriptor' is not a member of a base class of 'boost::graph_traits<G>' 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1> c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : see declaration of 'boost::graph_traits<G>::edge_descriptor' 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(27) : error C2868: 'boost::graph_traits<G>::edge_descriptor' : illegal syntax for using-declaration; expected qualified-name 1> with 1> [ 1> G=boost::bgl_named_params<boost::bundle_property_map<boost::adjacency_li st<boost::listS,boost::listS,boost::directedS,Host,SocketPair>,void *,Host,int>,boost::vertex_index_t,boost::no_property> 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(28) : error C2039: 'adjacency_iterator' : is not a member of 'boost::bgl_named_params<T,Tag,Base>' 1> with 1> [ 1> T=boost::bundle_property_map<boost::adjacency_list<boost::listS,boost::l istS,boost::directedS,Host,SocketPair>,void *,Host,int>, 1> Tag=boost::vertex_index_t, 1> Base=boost::no_property 1> ] 1>c:\program files\boost\boost_1_36_0\boost\graph\graph_traits.hpp(29) : error C2039: 'out_edge_iterator' : is not a member of 'boost::bgl_named_params<T,Tag,Base>' 1> with 1> [ 1> T=boost::bundle_property_map<boost::adjacency_list<boost::listS,boost::l istS,boost::directedS,Host,SocketPair>,void *,Host,int>, 1> Tag=boost::vertex_index_t, 1> Base=boost::no_property 1> ]

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