- Boost-users - lists.boost.org

Tag dispatching
by Hicham Mouline 04 Mar '09

04 Mar '09

Hello, I have a question about tag dispatching (for e.g. the std::advance() function in the std lib, as described for instance in http://www.boost.org/community/generic_programming.html#tag_dispatching) 1. The call to detail::advance_dispatch(i, n, category); I don't understand. category is a type not an object, it should be category(), right? 2. If I am correct, the tags are empty structs which I assume allows modern compilers (g++4, msvc8/9, intel) to optimize away the creation of that category object ? 3. If i am still correct, I have a tag which has no members except 1 static function that returns void. Would that optimization still apply? regards,

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Unhandled exception at 0x781451eb in ********.exe: 0xC0000005: Access violation reading location 0x0129ffff.
by ddribes 04 Mar '09

04 Mar '09

Dear Boost Users, I am new with Boost and I am facing a Unhandled exception. The program I am triying to use is working fine in release mode but crashing in debug mode. Maybe compiler options are not set correctly. Is there something specific for release and/or debug version ? Something to diseable exceptions ? I am working with VStudio 8. I've set the same compiler options for both but I still have the same error. Any ideas ? Thanks, -- View this message in context: http://www.nabble.com/Unhandled-exception-at-0x781451eb-in-********.exe%3A-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[boost-users][bind] binding std::for_each
by Igor R 04 Mar '09

04 Mar '09

Hello, I'd like to bind std::for_each with some other functor created on the fly, like this: struct A { void f(int, int); }; vector<shared_ptr<A> > vec; void f(function<void(void)>); // I want to call f() with a functor that would call A::f for every element in vec f(bind(&for_each, vec.begin(), vec.end(), bind(&A::f, _1, 1))); // doesn't compile f(bind(&for_each, vec.begin(), vec.end(), protect(bind(&A::f, _1, 1)))); // also doesn't compile Thank you.

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1.38 build cmake error
by Randy Heiland 04 Mar '09

04 Mar '09

Hello, Just downloaded 1.38 and trying to use the cmake build. I get my CMakeCache.txt setup the way I want, then: cmake . make sudo make install ... -- Installing: /usr/local/include//boost/xpressive/xpressive_static.hpp -- Installing: /usr/local/include//boost/xpressive/xpressive_typeof.hpp CMake Error at libs/preprocessor/cmake_install.cmake:31 (FILE): file INSTALL cannot find file "/Users/heiland/dev/boost_1_38_0/libs/preprocessor/include/boost" to install. Call Stack (most recent call first): libs/cmake_install.cmake:32 (INCLUDE) cmake_install.cmake:37 (INCLUDE) and sure enough, there's no .../preprocessor/include... heiland@Macintosh:~/dev/boost-build$ ls /Users/heiland/dev/ boost_1_38_0/libs/preprocessor CMakeLists.txt doc/ index.html module.cmake test/ Suggestions? OSX 10.5.6 cmake version 2.6-patch 2 thanks, Randy

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Including a source library with Boost.Build
by Z. S. O. 04 Mar '09

04 Mar '09

I have a source library I'd like to include in my Boost.Build project. The library consists of an assortment of header and cpp files in a folder next to the main cpp file and jamfile. It doesn't require any elaborate precompilation, so it should work just by #including the appropriate header files in the main cpp file (i.e., #include "FolderName/FileName.h"). My question is, do I need to do anything other than that to make this work? I'm getting an "undefined symbols" error, so clearly Boost.Build not finding something correctly.

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boost.serialization, asio and iostreams...
by Hajo Kirchhoff 04 Mar '09

04 Mar '09

(forwarded from asio.user as serialization questions might be more appropriate here) Hi all, I plan to use serialization and asio together to exchange 'command objects' between two applications. Basically marshalling an object and sending it to a remote application. There is a simple asio example using serialization, but there are two issues I'd like to improve. [1] I am concerned about performance. The example constructs and destructs an archive for every single object and uses stringstream, which creates and copies a string object. Wouldn't using asio::tcp::iostreams give better performance? and [2]: I would like to utilize the boost.serialize class registration system to allow peer programmers to create new objects. In the example I would need to send a 'type' and the size manually in a 'header' before I serialize and send the actual object. That would require a system wide enumeration or other 'type' mechanism. My idea is to require all objects be derived from a common polymorphic base and then serialize a pointer to the object. The archive would serialize the entire object and also send type information with it, so the receiver could reconstruct the object simply by receiving a pointer. class basic_command; class my_command:public basic_command; On the senders side: my_command dosomething; archive << &dosomething; On the receiver side: basic_command *next_command; archive >> next_command; next_command->execute(); This would have the benefit that new commands could simply be created by deriving from basic_command. It might also have performance consequences and I have one specific question: For this in order to work I would need to disable tracking for 'my_command'. Otherwise only the very first instance of archive << &dosomething would actually send something. Question: Can I 'reset' the binary archive such that the tracking information is reset, but not the type information? Or can I temporarily disable tracking for a class or for the next save/load operation? I don't want to globally disable tracking for my_command, because I cannot rule out that someone might actually want tracking for their object in a different archive (such as saving settings to disk). I'd love to hear from you and any comments are welcome. Has anyone already done this? What are your experiences? Regards Hajo

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[Units] implicit conversion of quantities
by Christopher Bruns 03 Mar '09

03 Mar '09

Kudos on the excellent implementation of the Boost.Units library. I am also very grateful for the extremely timely help I have got in the past from the principal authors Matthias Schabel and Steven Watanabe. Is there any way to force implicit conversion of Angstrom quantities to nanometer quantities in assignment and method calls using Boost.Units? I would appreciate any suggestions on how to get the final three method calls in the attached program to compile. I suppose I could overload the showBondLength() method in this example to take both types. I think I would prefer implicit conversion, if that is possible. I am using boost from subversion revision 51579, from March 3, 2009. --Chris Bruns /* =========== begin test program ========== */ #include <boost/units/systems/si.hpp> #include <boost/units/base_units/metric/angstrom.hpp> #include <iostream> namespace boost { namespace units { typedef metric::angstrom_base_unit::unit_type angstrom_unit; BOOST_UNITS_STATIC_CONSTANT(angstrom, angstrom_unit); typedef scaled_base_unit< si::meter_base_unit, scale<10, static_rational<-9> > > nanometer_base_unit; typedef nanometer_base_unit::unit_type nanometer_unit; BOOST_UNITS_STATIC_CONSTANT(nanometer, nanometer_unit); } } // namespace boost::units // No permutation of BOOST_UNITS_DEFAULT_CONVERSION macro has // *ever* had a measurable effect in my hands BOOST_UNITS_DEFAULT_CONVERSION( boost::units::angstrom_unit, boost::units::nanometer_unit ); using namespace boost::units; using namespace std; ostream& showBondLength( quantity<nanometer_unit> len, std::ostream& os) { os << len << endl; return os; } int main() { // These constructors all work; conversions are automatic quantity<nanometer_unit> len1( 0.152 * nanometer ); quantity<angstrom_unit> len2( 1.52 * angstrom ); quantity<nanometer_unit> len3( 1.52 * angstrom ); quantity<angstrom_unit> len4( 0.152 * nanometer ); // These three calls are OK, nanometer quantity is passed showBondLength(0.152 * nanometer, cout); showBondLength(len1, cout); showBondLength(len3, cout); // Explicit casts to nanometer are OK for angstrom quantities... // but yuck showBondLength( (quantity<nanometer_unit>) (1.52 * angstrom), cout ); showBondLength( (quantity<nanometer_unit>) len2, cout ); showBondLength( (quantity<nanometer_unit>) len4, cout ); // These all fail to compile. Users want implicit conversion here showBondLength(1.52 * angstrom, cout); showBondLength(len2, cout); showBondLength(len4, cout); } /* =========== end test program =========== */

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[regex] Context-sensitive replacement of text using regex_replace
by KEN RODE 03 Mar '09

03 Mar '09

I've been struggling with a problem with using regex_replace this afternoon, and I would appreciate some pointers on properly using the regex package. I've got a file that is similar to a CSS style sheet (it's actually a Qt style sheet) that contains color entries that similar to: rgb( 200, 255, 200 ). I've already successfully written some code that finds these patterns and replaced them with statically determined text, just to verify that I was able to locate them all properly. I have an application in which the color scheme of the user interface (specified in the style sheet) has to change between a daytime and nighttime color scheme. The nighttime color scheme is derived from the daytime color scheme by reducing the luminance of the colors. I'd like to generate the nighttime color scheme from the daytime scheme by extracting the components of the color and applying a calculation to them, then replacing the original text with the new text. The examples on the Boost site for regex_replace all demonstrate replacement with static text. I suspect that I have to do some sort of combination using regex_replace, regex_iterator, and match_results, but I can't quite wrap my head around the documentation for these classes to see how they interoperate. I would appreciate some pointers as to how to proceed.

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Re: [Boost-users] New and updated serialization performance results
by Brian Wood 03 Mar '09

03 Mar '09

Robert Ramey writes: >Given your interest in this topic, you might want to take a look at > >boost/libs/serialization/performance. > >included with the boost 1.38 package. > >There is a Jamfile.v2 in that directory and everything is set >up just the way boost testing is. The only difference is >that, using the GCC compiler, a function by function >time table is generated which pinpoints where time >is being consumed. This would help answer such questions >as "what if I replaced std::string with something else". > >I only included a couple of performance tests to >demonstrate the system. I havn't had time to make >a more complete set of tests. Ideally, I would like >to see your tests included for comparison. The source code on webEbenezer.net is not copyright protected, so anyone interested in doing what you suggest is welcome to do so. I doubt I'm going to be able to do that anytime soon. > >My question has always been that since serialization >(in at least the simpler cases) just boils down >to writing out the data, whether the code is >generated by one template or another shouldn't >make a big difference. That is, at the end of the >day, the sequence of operations should be pretty >much the same whether one is hand rolling the code >or whether it is generated by templates. > It may have something to do with your use of iostreams. I don't think that accounts for all of the difference, but my guess is it's a big part of it. In my opinion using insert with a hint is an easy way to improve the performance of the Boost Serialization library when loading instances of (multi)set, multi(map) and rb_tree. To my knowledge the only draw back with that is if someone is serializing from say a list<int> to a set<int> and the data in the list is not ordered. In that case using a hint would impede performance. Since that situation does not come up a lot, I think using hinted inserts as a default makes sense. We plan to change (this month) from a default of "regular" insert functions to hinted inserts for the types mentioned here. Currently we have a @hi option to turn on hinted inserts. That will change to @nohi to turn them off and could be used if data from a non-ordered list<int> is being sent to a set<int>. Brian Wood Ebenezer Enterprises www.webEbenezer.net "Then Samuel took a rock and set it up between Mizpah and Shen. He named it Ebenezer [Rock of Help] and said, 'Until now the LORD has helped us.'"

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[Review] RangeEx review extended to the 10th of March
by Thorsten Ottosen 03 Mar '09

03 Mar '09

Dear Developers and Users, The review period is extended one week. If you find this library interesting, please submit a review. The discussion so far may be found here: http://archives.free.net.ph/message/20090220.122836.73bdbd04.en.html Below you will find a description of the library and information on how to write a review. best regards Thorsten, review manager What is it? +++++++++++ The library provide two very useful extensions to the range library 1. Range-based algorithms. E.g. boost::sort( rng ); which is a convenient wrapper of instead of std::sort( boost::begin(rng), boost::end(rng) ); But the new interface also allows for more expressive code because (on the fly) composition of algorithms suddenly is possible. 2. Range adaptors. E.g. std::vector<int> vec = ...; boost::copy( vec | boost::adaptors::reversed, std::ostream_iterator<int>( std::cout ) ); where the expression "vec | boost::adaptors::reversed" wraps the iterators of the range on the left in reverse iterators. The library provides a wide range (no pun intended) of Range adaptors, and they are a powerful way to create ranges on the fly and pass them to algorithms. Getting the library +++++++++++++++++++ The library may be downloaded from http://www.cs.aau.dk/~nesotto/boost/range_ex.zip or from the Boost vault under "Algorithms". The docs may be browsed online here http://www.cs.aau.dk/~nesotto/boost/libs/range/ Please note that the documentation is integrated with the current Range ilbrary. Therefore the relevant sections for the review is http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/adaptors.html and http://www.cs.aau.dk/~nesotto/boost/libs/range/doc/algorithms.html The code may be browsed here: http://www.cs.aau.dk/~nesotto/boost/boost/range/ Notice the library is header only (exception: the adaptor tokenized() depends on Boost.Regex). Writing a review ++++++++++++++++ If you feel this is an interesting library, then please submit your review to the developer list (preferably), or to the review manager. Here are some questions you might want to answer in your review: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick - reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. Special considerations ++++++++++++++++++++++ Various RangeEx like libraries have been implemented in the past. You might want to compare with those libraries when you form your oppinion: 1. John Torjo's range lib http://rangelib.synesis.com.au/libs/boost-rangelib-20040913.zip http://torjo.com/rangelib/index.html 2. Adobe's ASL libraries include range-based algorithms: http://stlab.adobe.com/group__algorithm.html I'm looking forward to your review. best regards Thorsten, Review Manager

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