May 2009 - Boost-users - lists.preview.boost.org

Xpressive, symantic actions and combination enumeration
by Lee Simpson 07 May '09

07 May '09

Hi, First let me say. Awesome library and thanks for releasing it to the world. I'm looking for a way to apply all the currently queued semantic actions _without_ turning off backtracking. So, as the manual suggests, keep manages to apply the queued actions but it also turns off backtracking. The reason I am doing this is simple though unusual. I am trying to determine every possible match for a given input sequence, recording and ranking each one individually. A simple (contrived) example would be... input = "abcd"; expression = apply(+alpha[save_lhs(_)] >> +alpha[save_rhs(_)] >> eos) Ideally, applying the expression would yield the following combinations for 'lhs' and 'rhs' 1. "a","bcd" 2. "ab","cd" 3. "abc","d" The best solution I have come up with has an unacceptable time complexity. In short, the solution is to have a match assertion at the end of the expression which only succeeds on the nth try. I then use a while loop, executing regex_match with increasing values of 'n' until no more matches are found. Of course the problem with this solution is that the time complexity goes to n!+(n-1)!+(n-2)!... Any ideas?

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[rerepost][threads] recursive shared_mutex
by joaquin＠tid.es 06 May '09

06 May '09

I promise this is the last time I repost this; if I got no response I'll go and try somewhere else :-/ thanks for your patience. As the docs do not explicitly say otherwise, I guess I must assume that boost::shared_mutex is not recursive with respect to unique ownership, that is, the following behavior ensues: shared_mutex mutex; lock_guard<shared_mutex> lock1(mutex); lock_guard<shared_mutex> lock2(mutex); // DEADLOCK Is this so? In case boost::shared_mutex is indeed non-recursive, I've read the following assertion on Hinnant's paper N2406 (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2406.html ): "A recursive shared mutex could be built upon shared_mutex if desired, but this is not proposed." Does anyone has a reference on how to construct a recursive shared_mutex from a non-recursive one? Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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[optional]
by dariomt＠gmail.com 06 May '09

06 May '09

Hi list, In 'classic' C++ style I have signalled optional parameters in a function with pointers that might be null (I wouldn't like to create overloads for all possible combination of existing and non-existing parameters) e.g. // p1 is mandatory, p2, p3 and p4 are optional void f(const Param1& p1, const Param2* p2, const Param3* p3, const Param4* p4); And call it Param1p1; Param2 p2; Param4 p4; f(p1, &p2, 0, &p4); I thought I could use boost::optional like this void f(const Param1& p1, const boost::optional<Param2> & p2, const boost::optional<Param3> p3, const boost::optional<Param4> & p4); And call it Param1p1; Param2 p2; Param4 p4; f(p1, boost::optional<Param2>(p2), boost::optional<Param3>(), boost::optional<Param4>(p4) ); but I haven't seen this usage in the examples in the documentation of Boost.Optional. Is this usage correct? Are there any hidden drawbacks with this approach? TIA

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[Boost]bootsrap command not working.
by Jaiswal, Usha [OS-IE] 06 May '09

06 May '09

Hi, I need to build boost libraries for 64 bit platform for this I am using "bootstrap " command at command prompt but message is coming "bootstrap is not recognized as internal or external command, operable or batch file" What is the right way to use bootstrap command or if there is any bootstrap.bat or exe file, where is it present?? Thanks in advance for your help. -Usha.

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Re: [Boost-users] Stepping into a boost::function while debugging
by Neil Hunt 06 May '09

06 May '09

> > > I just hit step into until I get to familiar code. ... > > In Christ, > Steven Watanabe > > Ha! Somehow I think, Steven, there is no code which with you are unfamiliar. And I expect that even includes code you have never seen before. Neil

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[BGL] citing the Boost Graph Library
by Alejandro Marcos Aragón 06 May '09

06 May '09

Can anyone point me how to cite the Boost Graph Library in a paper? Is there any information in the boost website? Thank you all, Alejandro Aragón

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boost::mutex synchronization problem
by Zachary Turner 05 May '09

05 May '09

I've been trying to figure out if there's a simple way using condition variables and mutexes to design a function with the following properties (cliffs notes first, and then longer version in case it's not enough info): 1) there is a section of code in the function such that two threads cannot enter that section at the same time. 2) after leaving the section of code, the thread should wait for something to happen (signalled by another thread) 3) the waits in step 2 should be awoken in the order they occured. Basically there are many threads that may want to post requests to read/write from the network. So I have a bounded buffer implementation that holds "work items", which can be of read requests or write requests. writes return immediately, but reads block until the read is finished, which is determined by when the actual network thread processes the work item and signals something. read requests should be able to enter the queue regardless of whether another read request is already pending, but obviously the blocked threads should awake in the same order that items were inserted into the queue. I thought of making a condition variable for each read work item, and storing it in the work item that goes in the queue, so the network thread can notify that. But I feel like there should be a better way that doesn't require potentially arbitrary numbers of condition variables. Thanks

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What does "RALL-style" means ?
by ZouLei 05 May '09

05 May '09

Hi, everyone. When I refer the document of thread library, a word "RALL-style" appear in the introduction of the class lock_guard: This provides simple RAII-style locking of a Lockable object, to facilitate exception-safe locking and unlocking. I didn't got the main point of this word "RALL-style", could anyone tell me the meaning ? Thanks. Best wishes.

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Quickbook quick start
by Peng Yu 05 May '09

05 May '09

Hi, I wan to use Quickbook to generate documentation for my code to be submit to boost. I understand that Quickbook could help make the code and the documentation consistent. But there is no a tutorial webpage that describes how I can get started with Quickbook. I am wondering if there is somebody could give me some hints on how to use it? Regards, Peng

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Stepping into a boost::function while debugging
by Peter Åberg 05 May '09

05 May '09

Hi, Does anyone have a tip, suggestions or workaround on how one should do to step into the target function of a boost::function while debugging in VS 2008 (VC9), without wading through the boost::function implementation? I have looked around a bit now and have not found any solution except putting a breakpiont in the target function which may not be practical when one does not know which function it is. I get the feeling one have to wait for MS to add a feature like "step through code I don't want to see". But until then, what do you folks do? Designing with delegates in C++ feels a bit like a show-stopper for me until I can step into a delegate target function without getting lost in a haystack. Cheers, Peter

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