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RE: [Boost-users] Re: [boost::fsm] Accessing most recently posted event
by Marcin Tustin 04 May '05

04 May '05

> -----Original Message----- > From: Andreas Huber [mailto:ahd6974-spamgroupstrap@yahoo.com] > Sent: 04 May 2005 12:06 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] Re: [boost::fsm] Accessing most > recently posted event > > Marcin Tustin <mt <at> it-innovation.soton.ac.uk> writes: > > Sounds pretty good. Apart from ahving a member instead > of a function, > > and not bothering to clear the variable, this is pretty what I have > > done. Of course, I am still jury-rigging things for a > technology demo > > at this stage, rather than building a bulletproof library (which I > > leave for later, or better, other people). > > I see. Anyway, I've added triggering_event() to the to-do list... > I'll probably have something more bulletproof in about a month. If you haven't done this by then, I'll submit my patches to the boost list.

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RE: [Boost-users] Re: [boost::fsm] Accessing most recently posted event
by Marcin Tustin 04 May '05

04 May '05

> -----Original Message----- > From: Andreas Huber [mailto:ahd6974-spamgroupstrap@yahoo.com] > Sent: 03 May 2005 14:11 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] Re: [boost::fsm] Accessing most > recently posted event > > Hi Marcin > const event_base * current_event() const > > If the state entry was triggered by an event, current_event() > returns a pointer to the event that triggered the transition. > Otherwise, it returns 0 (e.g. the state was entered as a > result of calling state_machine::initiate(). > We could also name this triggering_event()... > > Thoughts? Sounds pretty good. Apart from ahving a member instead of a function, and not bothering to clear the variable, this is pretty what I have done. Of course, I am still jury-rigging things for a technology demo at this stage, rather than building a bulletproof library (which I leave for later, or better, other people).

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Regex & Autotools
by Foster, Gareth 04 May '05

04 May '05

Hello, Is there a sample autotooled project somewhere that would allow proper linking to Regex? Despite my best efforts with the macro provided for autoconf, I couldn't get my project to link. A sample working project is always the best way to go. Cheers, Gaz ********************************************** * http - http://planetearthworm.com/ * * mail home - earthworm(a)planetearthworm.com * * mail work - gareth.foster(a)siemens.com * **********************************************

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RE: [Boost-users] The Boost Community
by Foster, Gareth 04 May '05

04 May '05

Hello all, As a C++ developer, and a developer who is coming to appreciate the usefulness of Boost, I think this is a great idea. There isn't really a focal point on the web for C++ developers, at least not in the sense that Java developers have in java.sun.com, Mono developers have in go-mono.net, and as menitoned by somebody else, PHP developers have in php.net. Boost certainly has enough clout to make this happen. The idea of having the following C++/Boost oriented things on one site is fantastic. * blogs for people with influence over the development of the C++ standard (think planet), * blogs for heavy boost contributors (think planet), * documentation for C++/Boost with user anotations + * forum * news section feat. latest compiler news and c++/boost developments etc + see recent work murray cumming did in adding anotation facilities to gtkmm docs I am sure there are more ideas, but that summarises the best of them I hope. Useful links that might help get this off the ground. - http://www.planetplanet.org/ // will help with blogs - http://oswd.org // will help with site design - http://www.murrayc.com/temp/gtkmm_book_with_comments/html/ch13s02.php // murray's annotation effort It would be nice to get the site looking good right from the outset, whilst a "Name Competition" might not merrit a two month wait, I think perhaps a site design competition would. Look at sites like the Firefox page, a real central C++/Boost resource looking that professional would have to be good for C++ as a language. I hope my comments and thoughts add something to the discussion. All the best, Gaz > -----Original Message----- > From: Fernando Cacciola [mailto:fernando_cacciola@hotmail.com] > Sent: 03 May 2005 17:42 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] The Boost Community > > Hello people, > > In 1998, Bemans Dawes wrote the "Proposal for a C++ Library > Repository Web > Site" (you can find the paper in > (www.boost.org/more/index.htm) which > lunched the Boost we all know and love today. > The focus of the site was and is the production of high-quality > peer-reviewed C++ libraries. > Over the years, Boost grew as a community of experienced C++ > developers with > the will and means to share their expertise and work > contributing to the > highly respected Boost Libraries. Today, Boost is a somewhat > recongisable > part of the C++ programming community at large. > > Today, the way I see it, Boost as a community encompases only > the boost > developers, which are just a fraction of the larger C++ > crowd. There are > certainly Boost users, but I don't think we can say both > developers and > users form a community. I think is worth and in-the-spirit to > reach out for > ALL C++ programmers of ALL LEVELS around an "extended" Boost > Community whose > main sharing point is not just the submission of high-quality > libraries but > also the efficient and effective use of the language. > > A Boost Community site would focus not directly in the > Libraries produced by > Boost but on C++ itself as the great language we all love and > on fostering > proper use of it (which includes mixing it with other languages when > appropiate). > It would be volunteer-driven, just like the Boost libraries > are, so the site > would be moderated but open for external edition (I think a > wiki would > work). > I envision it having home page links to the fundamental > resources for C++ > programmers (CUJ,ACCU, "the" books, etc), blogs from > developers and users > (related to state of the art C++ and/or the boost libraties), > important C++ > related news (not just boost-library related news), reviews, etc... > essentially, everything the will of volunteers can bring on to the > community. The motto being "fostering proper use of C++". > A minimum of moderation would be required but I assume not much. > > I know there are other programmer communities around (even > C++ focused). The > reason I propose this here (around Boost) is becasue I think that a > community centered around the Boost Libraries but reaching > out could stand > out for its quality in the same way the Boost Libraries do. > I also know that a newsgroup or mailing list is a form of > community, and we > have c.l.cpp.m and c.s.cpp. But they lack the verstile structure and > dynamism of the today's virtual communities. Also, somehow I > believe that > centering a community around the Boost Libraries would spread > their quality > into the rest of the site; to some degree at least. > > I welcome comments, ctricticism and I call interested people > to put forward > concrete ideas. > > Best > > Fernando Cacciola > SciSoft > > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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[boost::fsm] Accessing most recently posted event
by Marcin Tustin 03 May '05

03 May '05

Is there a way that an event triggered on entry to a state can access the event that caused that state to be entered? I'm thinking of adding a line to the process_event method in a wrapper class derived from state_machine that stores the event object received as a way of doing this. Marcin Tustin IT Innovation Centre 2 Venture Road Chilworth Science Park Southampton, SO16 7NP, UK tel: +44 23 8076 0834 fax: +44 23 8076 0833 mailto:mt@it-innovation.soton.ac.uk http://www.it-innovation.soton.ac.uk

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config-files with program_options
by Anselm Kunstein 03 May '05

03 May '05

Hi, I'm trying ro read a config file with the program_options library, but I can't figure out how to read several sections in a config file whithout knowing (the exact) section names. For example I have a config file with N [blockn] sections (n=1...N) in my config file but I don't know N: [block1] name="Name section 1" [block2] name="Name2 section 2" . # there might or might not be more sections with the 'name' option . Is there any support for wildcards in option names so I could write something like options_description Opts_Desc("Config-File Options"); Opts_Desc.add_options() ("*.name", value<string>(), "Name of the block"); or is there a workaround for this problem? Thanks a lot in advance, Anselm Kunstein

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[MPL] is lambda<apply<...> >::type wrong?
by Vladim�r Marko 03 May '05

03 May '05

[using boost 1.32.0 with gcc 3.4.2 (mingw)] It seems to me that is_same< lambda<apply<type-list> >::type, apply<type-list> >::type::value is allways true. Is this intended or a bug? The exercise 1-6 in the MPL tutorial, http://www.boost.org/libs/mpl/doc/tutorial/exercises.html , reads "Build a lambda expression that has functionality equivalent to twice. Hint: mpl::apply is a metafunction!" where twice is defined as template <typename F,typename X> struct twice : apply<F,typename apply<F,X>::type> { }; and I think the obvious solution should be apply<_1,apply<_1,_2> > . The problem is that the expression apply< apply<_1,apply<_1,_2> >, add_pointer<_1>,int >::type doesn't compile at all. This is surprising since for example the expression apply< twice<_1,twice<_1,_2> >, add_pointer<_1>,int >::type yields int**** as expected. Is there some fundamental difference between the metafunctions twice and apply? My tests suggest that the compilation failure is caused by the property of lambda<apply<...> >::type described at the top. This seems pretty odd to me since lambda<T>::type is supposed to have a nested template class "apply" if T is a placeholder-expression and lambda<apply<type-list> >::type::apply refers to the boost::mpl::apply even if the type-list contains a placeholder-expression (making the whole apply<type-list> a placeholder-expression). Did I miss something? Thanks, Vladimir Marko

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dijkstra_visitor
by Andreas Fabri 02 May '05

02 May '05

Hello, I wrote my own dijksta visitor for the shortest path algorithm, and on an event I wanted it to write something in a bundled property of a vertex. However this didn't compile because the graph is a const&. Is there a way to solve this problem? Thanks in advance, andreas

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[conversion] RoundEven odd behaviour
by Vyacheslav E. Andrejev 02 May '05

02 May '05

Hello All I tried to use boost numeric conversion library and faced with strange feature of RoundEven that I can not comprehend or find expanation in the documentation. First I thought that this policy rounds float number to nearest integer, because RoundEven::round_style::value == std::round_to_nearest. But! This policy for example returns 2.0 for 3.0 as argument! cout << boost::numeric::converter< int , double , boost::numeric::conversion_traits<int, double> , boost::numeric::silent_overflow_handler , boost::numeric::RoundEven<double> >::convert(2.9) << endl; cout << boost::numeric::converter< int , double , boost::numeric::conversion_traits<int, double> , boost::numeric::silent_overflow_handler , boost::numeric::RoundEven<double> >::convert(3.0) << endl; cout << boost::numeric::converter< int , double , boost::numeric::conversion_traits<int, double> , boost::numeric::silent_overflow_handler , boost::numeric::RoundEven<double> >::convert(3.1) << endl; Output of the program above will be: 3 2 3 What is the cause of such strange behaviour? This is a bug or there is something that I don't understand? -- Vyacheslav E. Andrejev System Architect, Excelsior, LLC

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How to get type given pointer to base?
by Delfin Rojas 02 May '05

02 May '05

Hello all, I hope somebody can help me with this. What I want to do is the following: Let's say I have a templated class called Foo template<class U> class Foo { public: Foo(U * p) : m_p(p) {} ~Foo() {} U* getP() const { return m_p; } private: U* m_p; }; Now let's say I want to have a collection of pointers to Foo. What should I do? The possibilities I can think of are the following: 1) Create a class FooBase and have Foo inherit from FooBase. FooBase is non-templated so there should be no problem with having a collection of pointers to FooBase where I can put instances of Foo. The problem with this approach is that given a FooBase* in that collection I could not use the getP method because I would not know what type of Foo it holds. 2) Create a boost::variant of all the possible types of Foo<U>* I want to have. Then have a collection of this FooVariant. Using static visitation I can obtain the original type of Foo<U>* in a given FooVariant. The problem with this approach is that I get an ICE from VC++ 7.1 when the type of U gets too complex (shared_ptr to another type for example). Have I overlooked something? Is there a better technique for what I want to achieve? Any help would be great, Thanks Delfin Rojas

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