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

Finite State Machine example
by b_trask 28 Apr '03

28 Apr '03

Hello, I am looking at http://www.boost.org/libs/mpl/doc/paper/html/example.html I have a dumb question or perhaps I am missing something (or both). Where is the state_machine class template that the player derives from using the curiously recurring template pattern? class player : state_machine<player> // where is the code for this class? { Regards, Bruce

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enable_shared_from_this and constructor
by Petr Ferschmann 28 Apr '03

28 Apr '03

Hello, why is not possible to call this: -- cut here -- #include <boost/enable_shared_from_this.hpp> class Trida; boost::shared_ptr<Trida> trida; class Trida : public boost::enable_shared_from_this<Trida> { public: Trida() { trida = this->shared_from_this(); }; }; int main() { boost::shared_ptr<Trida> tr(new Trida()); return 0; } -- cut here -- It throws in constructor of shared_count(weak_count const & r). I think the problem is that there is no one shared_ptr instance that owns object tr yet when calling constructor. May be it is BUG (and I don't know how to handle that). Can be at least note in documentation? -- Petr "Fers" Ferschmann -=[ petr(a)ferschmann.cz ]==[ http://petr.ferschmann.cz/ ]=- -=[ Koukni na http://www.postcard.cz/ ]==[ +420 604/781 009 ]=- GPG Fingerprint: [83B0 6378 7A9D D993 035E 60BD FEEC F665 D2C8 1B9A] [Non-text portions of this message have been removed]

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RE: [Boost-Users] Circular Buffer
by Tom Matelich 28 Apr '03

28 Apr '03

I've seen several implementations of things like this come up on the boost mailing list in the past. My impression is a lot of people gave up when confronted with all the different options that would have to be considered to make it through a Boost review. I did see cyclic_buffer.zip in the Files section at the old yahoo group site ( http://groups.yahoo.com/group/boost/files/ ). > -----Original Message----- > From: Joe Mariadassou [mailto:joemar@vcisnet.net] > Sent: Wednesday, April 23, 2003 11:56 PM > To: Boost-Users(a)yahoogroups.com > Subject: [Boost-Users] Circular Buffer > > > Does boost or any other open source have an implementation of > a bounded > circular buffer? My search in boost and google yielded naught. > The main purpose of this container is to pipeline messages in > a typical > producer-consumer scenario. I was surprised not to find any > implementation. > TIA > Joe > > > > [Non-text portions of this message have been removed] > > > ------------------------ Yahoo! Groups Sponsor > ---------------------~--> > Get 128 Bit SSL Encryption! > http://us.click.yahoo.com/xaxhjB/hdqFAA/bW3JAA/EbFolB/TM > -------------------------------------------------------------- > -------~-> > > Info: <http://www.boost.org> > Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> > Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> > > > Your use of Yahoo! Groups is subject to > http://docs.yahoo.com/info/terms/ > > ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

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uBlas - diagonal_matrix
by Patrick Kowalzick 28 Apr '03

28 Apr '03

Dear all, I can use a banded_matrix to represent a diagonal matrix, but while some math for a diagonal matrix is a little bit easier than for a rectangular matrix, it would be nice to have such a type. In my case: I use a SVD A = U * S * V.T to calculate the moore-penrose-inverse A+. Therfore I use A+ = V * S+ * U.T (i do not remember exact, but focus on S+) with S+ as the moore-penrose-inverse of S which is very easy to calculate. but to use something like pinv(S) , do I need a symmetric_matrix type? Or can I implement a pinv() for a banded_matrix wich must fulfil the constraint of being diagonal? Thanks a lot Patrick

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Re: pool_allocator problems on VC7.1 (real rele ase)
by scleary＠jerviswebb.com 26 Apr '03

26 Apr '03

> -----Original Message----- > From: John Harris [mailto:john.harris@tradingtechnologies.com] > > I can test this for you tomorrow (I'm about to go drinking now). In > return, could you possibly tell me how to change pool_allocator so > that it uses my own tag? My goal is to have a totally local > allocator for some special parts of the code. Why, BTW, does it have > to use the Singleton pool interface instead of the object pool > interface? The latter, I think is what I'm after. I'm going to start with a brief overview of the Boost.Pool interfaces: pool<> (pool.hpp): "The" pool interface. Provides allocation and deallocation of memory. object_pool<> (object_pool.hpp): Restricts access to the pool<> interface. Provides allocation and deallocation of memory for a single object type; and, when destroyed, will call the destructor for any non-deallocated objects allocated from that object_pool. singleton_pool<> (singleton_pool.hpp): Provides access to the pool<> interface as a singleton, distinguished mainly by size of the memory allocations and a tag. pool_allocator<> (pool_alloc.hpp): Restricts access to the singleton_pool<> interface. Provides a Standard-compliant Allocator interface. To answer the specific questions: 1) The pool_allocator<> (and fast_pool_allocator<>) can be relatively easily extended to use other tags for the singleton_pool<> interface underlying them - pass an additional template parameter (after the UserAllocator parameter), defaulting to the currently-used tag. This is a good idea, and I'll put it in when I can. 2) pool_allocator<> uses the singleton_pool<> interface instead of the object_pool<> interface for the following reasons: A) Standard Allocators only handle the allocation and deallocation of memory, and do not deal with actual object types [+]. The intent of object_pool<> is to cleanly call destructors for objects that were never deallocated. Such an action: 1) is unneeded (since all containers should free whatever memory they allocate, and destroy any objects they construct), and 2) would cause the Allocator to get into construction/destruction semantics, which is contrary to the Standard Allocator concept. B) Standard-compliant Allocators that can be used with STL-provided containers must be stateless. This requires an underlying singleton interface. Encapsulating a non-singleton interface within the Allocator, or even sharing one with the handle/body idiom does not satisfy the stateless requirement. [+] The object-related Allocator requirements (construct()/destroy()) do not have anything to do with allocation/deallocation, and are generally considered to be a useless overspecification. Please let me know if I haven't been clear enough - I've been a little lacking in sleep lately ;) -Steve

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RE: [Boost-Users] NRVO (was Re: "Correct" way to return empty shared_ptr?)
by dick.bridges＠tais.com 25 Apr '03

25 Apr '03

return shared_ptr<int>(); works with VC6.0 but elicits the [AFAICT] uninformative <emsg>parse error before `;'</emsg> from gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-110). Drat! "Duane Murphy" <duanemurphy@mac To: "Boost Users" <Boost-Users(a)yahoogroups.com> .com> cc: Subject: RE: [Boost-Users] NRVO (was Re: "Correct" way to return empty shared_ptr?) 04/24/2003 09:40 AM Please respond to Boost-Users --- At Thu, 24 Apr 2003 16:56:40 +0100, Ben Hutchings wrote: <snip> shared_ptr<int> maybe_get_a_pointer() { return shared_ptr<int>(); } is perfectly reasonable and can also be optimized. Is there more recent and complete discussion concerning this optimization? Is naming actually required? ...Duane Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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RE: [Boost-Users] Re: pool_allocator problems on VC7.1 (real rele ase)
by scleary＠jerviswebb.com 25 Apr '03

25 Apr '03

> -----Original Message----- > From: John Harris [mailto:john.harris@tradingtechnologies.com] > > Since it seems to work on VC7.1, it would be nice if the author had > access to that compiler and could do some testing. In the mean time, > I'll try some stuff with this new toy and report any further problems. Some command-line tools ship with their DDK, so I do have a version of "cl.exe" that reports "13.00.9176" - no idea how this fits in with the VC versions, though. And the DDK doesn't include an STL anyway. There is one "common" failure case with some implementations of STL containers: passing 0 to Allocator::deallocate. When used with std::allocator, the 0 is passed through to operator delete() which of course ignores it. When used with pool_alloc, this generally causes a segfault. IIRC, STLPort's std::vector will do this if you construct & destroy an empty vector. Since I don't have the VC STL, could you do that test case for me? Thanks, -Steve

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MP3 and C++
by steelgig 25 Apr '03

25 Apr '03

Hi, I'm working on a project for the university and I'm looking for some C++ library or application that could help me. My goal is to extract some kind of information related to the spectra of a signal coded in MP3. I'm looking for a spectrum analyzer that localizes peaks in the power spectrum (better if it works on a user-specified band) and allows the detection of the temporal occurence of each peak and its intensity. I also need to retrieve some sample of frequency components (or the MDCT coefficients) near the identified peaks. Every suggestion is welcome (even something that satisfies only partially the requests or that indicates a better place to found an answer to this message). Thanks in advance for the help, Gio PS: even some function that works on the MP3 file without decoding it, for example only partial decoding actions (IMDCT, Huffman decoding) or subband value retrieval function, could be useful.

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Circular Buffer
by Joe Mariadassou 24 Apr '03

24 Apr '03

Does boost or any other open source have an implementation of a bounded circular buffer? My search in boost and google yielded naught. The main purpose of this container is to pipeline messages in a typical producer-consumer scenario. I was surprised not to find any implementation. TIA Joe [Non-text portions of this message have been removed]

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Test for endian using MPL or PP(Wave?)
by Mike Wilson 24 Apr '03

24 Apr '03

Hi, There is an application I use that always produces a little endian binary file. I have written a program to process this file. As my program can port to both little/big endian platforms I have a #define (LITTLE_ENDIAN_TARGET) acting as a flag for the necessary byte swapping that is needed on the big-endian platforms. I was wondering if there is a better way to do this, so I searched the Web & boost archives. I found the following code snippet in the boost archives. bool isLittleEndian() { int temp = 1; return (*(char*)&temp) != 0; } which is of some help (eliminating my #define). However, I was wondering if there is a PP or mpl way of testing for endian-ness at compile time. For example, I'd like to do something like the following: const bool IsLittleEndian = ..to be determined automatically..; I've got a gut feeling that I can't do the above at complile time, but maybe something like Wave may do the job? Thanks for any assistance in this matter. Mike

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