April 2006 - Boost-users - lists.preview.boost.org

Using bind/lambda to extract graph bundled properties from overloaded operator[]
by Sean Kelly 25 Apr '06

25 Apr '06

Hi All, I'm attempting to use bind to extract bundled properties from a adjacency_list graph via the syntax below. ToyGraph g; ToyGraph::vertex_descriptor v; bind(&ToyGraph::operator[], ref(g), _1)(v); this fails to compile (I assume because opertor[] is overloaded) bind(&ToyGraph::swap, ref(g), _1)(g); works fine -- any suggestions on how to make the former work are appreciated. thanks Sean Windows XP Professional SP1, Boost 1_32_0

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Problem with iterator, map, shared_ptr and templated class
by James Hughes 25 Apr '06

25 Apr '06

Hello all, I am a bit stumped by a compile fault.. This is a fragment of the code template<typename T> void LCLogSource<T>::SetLoggers(std::map<T, boost::shared_ptr<LCLogHandler<T> > > &LogMap) { typedef std::map<T, boost::shared_ptr<LCLogHandler<T> > > handlerMap ; for (handlerMap::iterator pos = LogMap.begin(); pos != LogMap.end(); ++pos) // **** compile error here { yada yada I get a compile fault on the for line, 'expected ; before pos'. Now this fault has only started happening since I decided to template this class. It appears that the combination of the template, and the complexity of the map declaration is causing things to go awry, and I don't know why. I have tried a few alternatives but always get a problem of some description. Is there some reason I cannot use iterators on a stl::map where the map key defn. depends on the template parameter? In case this is nothing to do with the shared_ptr in the map, does anyone have a list where templates programming is discussed so I can post there? James

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General Boost documentation
by John Krajewski 25 Apr '06

25 Apr '06

I'm new to generic programming and finding the various concepts used in Boost quite confusing (named parameters, property maps, etc). Is there general documentation for the programming methods used in Boost? Perhaps a good book to buy?

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Graphs - push/relabel algorithm
by Leandro Melo 25 Apr '06

25 Apr '06

Hi. One of the restrictions of boost's graph push relabel algorithm is the existence of 'reverse' edges in the graph. I don't know exactly what the procedure should be for graphs already have the 'reverse' edges. For example, if I want to compute a max flow of an undirected network (it's not the rare) - in this case the networks would already have the reverse edges, which are not necessary set with capacity 0, as the algorithm requires. From what I can see in the implementation (a very fast look), the algorithm would not work correct in this cases. Maybe I'm 'thinking' wrong. Can anyone help me understand that? Thanks. -- Leandro Terra C. Melo

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BGL: filtered graph question
by Sebastian Weber 25 Apr '06

25 Apr '06

Hello everybody! I use the filtered_graph framework to restrict a BFS visit to a small region on my graph. BUT, I provide the starting vertex to the BFS routine by a vertice_descriptor of the underlying/unfiltered graph. Of course, this vertice descriptor matches the predicate. My code compiles fine, but I started to ask myself if this actually behaves correct? As I could not find a hint within the docs, does someone know? Greetings, Sebastian

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[BGL] Neighbourhood as a subgraph.
by Seweryn Habdank-Wojewódzki 25 Apr '06

25 Apr '06

Hi! Did any one check how to get neighbourhood of the node from given graph with respect to the properties or connections? Like in example below: V = { 1, 2, 3, 4, 5 }; E = { (1,2), (2,5), (5,4), (2,4), (1,4), (1,3), (3,4) }; So if there is no property, let assume that we are interesting in searching neighbourhood level 1 of point 1 we will have {1,2,3,4} level 2 {1,2,3,4,5}, but neighbourhood level 1 of point 4 is {1,2,3,4,5}. Of course I am interesting in copying proper edges too. If we have numerical properties on edges we could define (as on all problems with paths) that distance between node A and B is a sum of properties between them. And if we set adjacent matrix as 0 1 3 2 0 1 0 0 1 1 3 0 0 2 0 2 1 2 0 2 0 1 0 2 0 Than neighbourhood of level (or in that case "distance") 1 of point 1 is {1,2} level 2 {1,2,4,5}, and for point 4 level 1 {2,4}. The question is. If algorithms "breadth_first_*" will give me all functionality for that or not? Regards. -- |\/\/| Seweryn Habdank-Wojewódzki `\/\/

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proposal for a clearly visible roadmap on boost.org
by miele di vespa 25 Apr '06

25 Apr '06

Hi all, I am a programmer interested in using boost in my application. I was studying the statechart library that, how I learnt from http://www.boost.org/more/formal_review_schedule.html, is part of boost CVS but not yet part of an official boost release. I was wandering in boost.org site looking for sort of a roadmap telling me the status of each new library, for example: statechart;Accepted -- Added to CVS;will be in 1.33.4;august 2006 I think that this kind of roadmap will be very useful for end-user evaluating the adoption of boost library and it should be in a very noticeable place in the boost.org web site. Thank you for your attention. Best regards, Alessandro Gentilini

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Macro definitions in the wave
by Anatoli Sakhnik 25 Apr '06

25 Apr '06

Hello, boost users! This question is adressed rather to wave developers. Why doesn't the wave expose possibility to query or iterate over the map of macro definitions. This would be very useful for manipulation on the context. Say, one could serialize macro definitions to the disk, then there would it be possible to continue preprocessign the file without walking over unchanged included headers. Currently, I myself collect macro definitions through the ContextPolicy, but this doubles memory consumption. Thank you! -- Anatoli Sakhnik.

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Re: [Boost-users] General Boost documentation
by James Hughes 25 Apr '06

25 Apr '06

> James Hughes wrote: > > >Slightly off topic, but what I would find a great help with > regards to > >learning Boost is a better description on what each library > can do, and more > >importantly, what problems it solves. > > > >For example, perhaps someone has a problem they need to > solve that a Boost > >lib will help with, but just reading through the top level of the > >documentation may not give them enough of a hint that this > is the case. > > > > > This issue has recently been the subject of discussion on the > developer > list. I can't remember exactly what the outcome was, though. > If you have > any concrete suggestions on how to make the library overview without > making it unreadable long, we'd love to hear them. Even a simple list of common problems solved (or if inapplicable, the area of computer theory covered by the component) at the top level of the docs would help I think. Some (most) of the short descriptions are already pretty good (I think that now, but when I first looked they were rather bewildering), but for the more complicated libs, maybe more information would be useful. For example, Property map is described thus "Concepts defining interfaces which map key objects to value objects". At first glance this seems to be pretty similar to stl::map (to someone new perhaps to both Boost and STL), so perhaps needs little more explanation at the top level as to what it's for. > > >My pet one is simple loading and saving of configuration > information in XML. > >Which library should/can I use for that? Serialisation? Or > is there a better > >option? Or is there a boost lib in the wings perhaps aimed at that > >particular task? > > > > > The property_tree library currently under review can do exactly that. > The Serialization library can load and save XML, but only in its own > particular format, i.e. you cannot make it load a schema you have > externally defined. > > >Another is Boost::graph - I see lots of questions about it > on the list, but > >what real world problems does it solve? > > > > > That's what studying computer science is about: learning how to solve > problems. Having learned graph theory, the simple statement that > Boost.Graph helps with graph problems is worth a lot to me. > There is no > way to explain in a short statement what kinds of problems > the library > solves. Many kinds problems can be mapped to graphs. > Already did that - although it was twenty years ago! Problem with Computer Science degrees I always thought (and that's what I did), was the lack of real world application. A lot of theory, and *some* good stuff on application, but not enough. Graph theory is a good example - I understand the concepts (even from twenty years ago), but have never been given enough examples of real world application to be able to apply it myself (perhaps I have never had a need of course!). James > Sebastian Redl > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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[date_time] Need help with a couple simple problems
by Scott 25 Apr '06

25 Apr '06

I've spent a couple hours looking over the docs for the date-time library but still haven't been able to figure out how to do what I need to do. I'm hoping someone on this list can shed some light on how to solve my problems. I'm creating a logging system for our software and each log is timestamped. I want to store in a file the boost::posix_time::ptime of each log. I realize ptime supports boost::serialization, but we had to pull the boost::serialization code from our server because of really strange errors (DLL exceptions, DLLs getting unloaded while serializing, etc). What's the best way to serialize/deserialize a ptime? The file is in a binary format, so the most compact format is preferred. I'm storing the ptime for each log in UTC, however I would like to convert it to local time when the log is displayed. I saw all kinds of conversions to local time, but all of them had the time zone hard coded. Is there a simple way to just convert UTC to the time zone of the computer? Thanks for any and all help, Scott

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