September 2009 - Boost - lists.preview.boost.org

[fusion] useful as_variant in spirit2
by Christian Holmquist 26 Sep '09

26 Sep '09

Good day everyone, The function in boost\spirit\home\support\detail\as_variant.hpp seems to have no dep. on spirit, and it's a useful utility that would fit into fusion/support/as_variant.hpp> IIUC it's a meta function that computes a variant<T0, ..., TN> from a fusion sequence<T0, ..., TN>. I think there's no reason for a runtime counterpart, i.e. as_variant<Seq>::type is a valid expression but as_variant(Seq) and result_of::as_variant<Seq>::type is not. Thus, the function is already complete. Does it seem reasonable to you to include in fusion? The work of moving it would be to only update the docs, as spirit2 probably does excessive testing of this function anyway. I could collect the docs from other parts of fusion, and put together a separate test file if needed. All real work is already done, just presentation and formality that is lacking. Have a nice weekend, Christian

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Tools for singleton or monostate or alternative
by Mateusz Loskot 25 Sep '09

25 Sep '09

Hi, I would like to kindly ask for advice in finding tools within Boost collection that could help me to solve my problem. I'm developing a library (it will be used as dynamic-linked library). I need to manage a bunch of related values (numbers) globally. All values are shared across a client process, by its all threads, so thread-safety is under consideration. Mostly, a client needs to read the values (defaults) and sometimes, very rarely, a client needs to re-set the values. I consider to implement it using singleton or monostate pattern with thread-safety (and DLL-safety in mind), so actually Tobias Schwinger's Singleton library [1] would solve this problem well. However, I would prefer something from the Boost collection - Tobias' lib hasn't been approved [2], quite pity as Boost lacks of such tool, IMHO. Also, I've considered digging out singleton stuff from the boost::pool::detail, but I'm not convinced to this idea. I haven't found anything related to monostate patter in Boost. Would anyone suggest a tool available in Boost that would be usable to wrap up some basic but robust solution for my problem? By the way, any plan for update and another round of review of Tobias' library? [1] http://torjo.com/tobias/index.html [2] http://lists.boost.org/boost-announce/2008/01/0171.php Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org

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[rdb] Uploaded 0.0.07
by Jean-Louis Leroy 25 Sep '09

25 Sep '09

This version features : * insert...set syntax (but no insert...select yet) * update [where] * delete from [where] * create and drop follow the same syntax pattern as the others * attempts to simplify the internals (in insert - select still needs a second look) * some concept checks It's *beginning* to look like something one could use in simple real apps. What's missing before it qualifies is imo `like', 'exists' and transactions. That should not take long. This version compiles with msvc9 and gcc 4.4.1. I tested on Win32 with an Access db via ODBC. The sql engine tests pass on Linux but I have not tried the ODBC test suite on Unix yet. If somebody tries it, please tell me. I have changed the naming scheme : first number is major revision ; second is the milestone (crud with direct execution ; transactions ; prepared statements ; dialects ; constraints ; dynamic sql - which btw I am now nearly sure I can fit elegantly in my framework ; views). Third number is just there for getting ++'ed. The test suite is still the doc but after the transactions I'll begin documenting. Probably with QuickBook. It's funny to see that some people are still downloading 0.04. As I write this the downlaod count bumped to 21 :-D To avoid confusion due to the change in the versioning scheme I deleted the old versions. J-L

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[interprocess][multi_index] emplace() is not sufficient for maps
by Thorsten Ottosen 25 Sep '09

25 Sep '09

Hi Ion and Joaquín, This issue is related to node-based containers. I think you both have added emplace() to provide efficient in-place construction. However, I often encounter a situation where emplace() is not sufficient for me. The situation is characterized by the need to calculate the key after the mapped value (a heavy object) has been placed in the pair. To calculate the key the mapped value needs to be modified (the key is calculated as a side-effect). I therefore suggest that we add a new function: typedef ... map; map m; map::node_ptr p = m.get_node_ptr(<like emplace, but only for constructing the mapped value>); p->pair.first = modify( p->pair.second ); m.insert( boost::move(p) ); Thoughts? -Thorsten

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Boost build problem
by Emil Dotchevski 25 Sep '09

25 Sep '09

I'm trying to use <link>static and <runtime-link>static with my own code, which depends on boost filesystem, and I have the problem that the linker is passed libboost_filesystem-vc80-mt-sgd-1_41.lib while the debug\link-static\runtime-link-static folder has libboost_filesystem-vc80-sgd-1_41.lib. (I've built bjam from the latest trunk sources and I'm using the latest trunk revision of boost build.) HALP! :) Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode

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[rdb] Uploaded 0.0.08
by Jean-Louis Leroy 24 Sep '09

24 Sep '09

Tonight: * insert...where (but doesn't check consistency between insert list and values returned form select) * like J-L

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boost::variant -- this code compiles fine -- I think it should not compile
by Peter Foelsche 24 Sep '09

24 Sep '09

#include <boost/variant.hpp> struct test { }; int main(int argc, char **argv) { boost::variant<std::string, int, double> s; boost::get<test>(s); return 0; }

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Matrix Library
by Cem Kalyoncu 24 Sep '09

24 Sep '09

As a part of our graphics study, we have built a 2D matrix class to implement few matrix operation. After the study we have expanded our aim for matrix operations system and started building a matrix and possibly a math library. Currently matrix library is quite near to the finish. To make it as generic as possible, we have used templates. Current state of the project can be accessed from http://sourceforge.net/projects/mathlibcpp/ (SVN: https://mathlibcpp.svn.sourceforge.net/svnroot/mathlibcpp/) A simple search revealed that there is no matrix module for boost libraries. We are willing to resolve compatibility issues and lend our support this module. However, before taking any action, I would like to ask your opinions. Thanks in advance, Cem Kalyoncu Following functions exists in the library: Set/Get/GetData/() Resize/GetSize/GetCols/GetRows isSquare/isIdentity Compare/==/!= =/Copy constructor/CopyTo [Row|Col|]Min/Max/Average/Sum/Median [Row|Col]MinIndex/MaxIndex SortRows RemoveCol/RemoveRow matrix operators (+, -, *, +=, -=, *=) scalar operator (+, -, /, *, +=, -=, *=, /=) Transpose/Determinant/Inverse/Minor/Cofactor/Adjoint Uses a managedbuffer and allows temporary matrixes which are not copied Identity/ZeroFilled/RandomFilled/RobertsCross/SobelX|Y conversion to string and output to a stream is supported

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pool allocation
by Stefan Strasser 24 Sep '09

24 Sep '09

I took a closer look at Boost.Pool today to replace some default allocation of small objects. what I found there was a little disappointing, at least for my use case. the object_pool has 2 major downsides: - no dynamic block allocation - destroying one(!) object is O(N), with N being the number of unused objects in the pool so I wrote some code for my own use. I'm not suggesting this code should be added to boost, but something like it. struct A{ ... }; { pool<A,100> pool; A *a; for(int c=0;c<250;++c){ a=pool.new_(); // O(1) } pool.delete_(a); //O(1), destructs } //destruction of 249 objects, O(N) this allocates 3 memory blocks. but it also has one pointer memory overhead per object, to achieve constant time deletion. but you can use that pointer while the object is in use, which was what lead to this code: I needed to store unused boost.intrusive nodes: struct A : intrusive::[s]list_base_hook<>{ ... }; { [s]list_pool<A,[s]list_base_hook<>,100> pool; //same as above } this has no memory overhead, as the list hook can be used by the pool. here's the code: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=intrus…

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[asio] Mixing of sync and async calls
by Roland Schwarz 24 Sep '09

24 Sep '09

Is it legal to mix async and sync function calls? (I was not able to find the answer in the doc.) E.g. socket.async_read_some(buf); socket.write_some(otherbuf); Also when in a blocking sync call, will it be possible to "cancel" it from another thread, e.g. by posting to the io_service which will invoke a close on the socket? Thank you in advance. -- _________________________________________ _ _ | Roland Schwarz aka. speedsnail |_)(_ | sip:speedsnail@ekiga.net | \__) | mailto:roland.schwarz@chello.at ________| http://www.blackspace.at

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