March 2009 - Boost-users - lists.boost.org

[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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[Proto] Splitting AST
by Joel Falcou 03 Mar '09

03 Mar '09

Let's say I want to take an expression involving operators +,-,*,/ and a function split. What I want to do is writing a transform taking such an expression and returning a fusion::vector or list (I guess) of expressions containing all sub-expressions of the original AST only separated on each insatcne of a split call. E.g : Xpr = a+b+split( c*d + split(e-f)); is turned into Xprs = [ a+b+placeholder<1>, c*d+placeholder<2>, e-f]; I guess I should use the State/Data parameters of the transform but i can't get the thing right. Any hints on how to tackle this without losing hairs ? -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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using boost::filesystem::delete
by Sean Farrow 03 Mar '09

03 Mar '09

Hi: I have a boost::filesystem::wpath object. I need to firstly check if the file exists, and secondly delete and check the file has been deleted. How would I go about this? I've loked at the reference and carn't seem to make sense, are thee any examples of both these functions? Any help apreciated. Sean.

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Installing boost 1.38 in UBUNTU 8.10
by jan acosta 03 Mar '09

03 Mar '09

Hey guys, I am having trouble linking my boost libraries to a program I am trying to install. I need to install boost versions above 1.37 and ubuntu doesn't have packages yet for anything above 1.35. I am trying to install this program: http://webapp.dam.brown.edu/wiki/SciComp/InstallHedgeFromGit I followed the steps in his wiki but I always get this error message: g++ -pthread -shared -Wl,-Bsymbolic-functions build/temp.linux-x86_64-2.5/src/cpp/cuda.o build/temp.linux-x86_64-2.5/src/cpp/bitlog.o build/temp.linux-x86_64-2.5/src/wrapper/wrap_cudadrv.o build/temp.linux-x86_64-2.5/src/wrapper/mempool.o -L/home/supacreative/pool/include/lib -L/usr/local/cuda/lib -lboost_python-gcc41-mt -lcuda -o build/lib.linux-x86_64-2.5/pycuda/_driver.so /usr/bin/ld: cannot find -lboost_python-gcc41-mt collect2: ld returned 1 exit status error: command 'g++' failed with exit status 1 I can't get past this error. I've tried using the export command using: export LD_LIBRARY_PATH=/home/(my username)/pool/lib:$LD_LIBRARY_PATH and I still get the same error message. I even added the library folder into my ld.so.conf.d and ran ldconfig to restart ld, but I still get the same error. Please help. Jan

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Template method applied to template object
by Adrien Chauve 03 Mar '09

03 Mar '09

Hi all, The following lines don't compile with g++ (4.3.2) whereas it's ok with msvc 9. struct Foo { template<class T> unsigned int foo() const { return sizeof(T); } }; struct OtherFoo { template<class T> void f(const T& t) { t.foo<double>(); } }; int main() { Foo foo; OtherFoo other; other.f<Foo>(foo); return 0; } The ouput is : test.cpp: In member function ‘void OtherFoo::f(const T&)’: test.cpp:17: erreur: expected primary-expression before ‘double’ test.cpp:17: erreur: expected `;' before ‘double’ Does anybody know a workaround ? Thanks, Adrien

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Error when trying to build boost 1.38.0 with msvc 8.0
by LPE 03 Mar '09

03 Mar '09

I'm trying to build boost 1.38.0 on Windows, with MSVC 8.0 and bjam 3.1.17, and I get this error : D:\boost_1_38_0>bjam -q -j3 -d+2 --toolset=msvc --build-type=complete Skipping build of: ./headers <build>no in common properties Skipping build of: ./headers <build>no in common properties Skipping build of: ./headers <build>no in common properties Skipping build of: ./headers <build>no in common properties warning: Graph library does not contain optional GraphML reader. note: to enable GraphML support, set EXPAT_INCLUDE and EXPAT_LIBPATH to the note: directories containing the Expat headers and libraries, respectively. warning: skipping optional Message Passing Interface (MPI) library. note: to enable MPI support, add "using mpi ;" to user-config.jam. note: to suppress this message, pass "--without-mpi" to bjam. note: otherwise, you can safely ignore this message. Building Boost.Regex with the optional Unicode/ICU support disabled. Note: Please refer to the Boost.Regex documentation for more information Note: this is a strictly optional feature. Skipping build of: ./build_all <build>no in common properties Skipping build of: ./build_all <build>no in common properties Skipping build of: ./build_all <build>no in common properties Skipping build of: ./build_all <build>no in common properties common.mkdir bin.v2 if not exist "bin.v2\\" mkdir "bin.v2" 'C:\Documents' is not recognized as an internal or external command, operable program or batch file. ...skipped bin.v2\libs for lack of bin.v2... Thanks in advance.

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Re: [Boost-users] Installing boost 1.38 in UBUNTU 8.10 (Alain Leblanc)
by jan acosta 03 Mar '09

03 Mar '09

Did you verify that you have a file named boost_python-gcc41-mt.so or boost_python-gcc41-mt.a? Depending on the options you used when you installed boost they may have a different name, such as without the gcc42 or with an extra -1.38. Yes I verified that those are the names. My compiler version is gcc41. I had to downgrade from gcc42 to gcc41 because Cuda has problems running at higher versions of the compiler. To install hedge or pycuda, I only have to put boost_python-gcc41-mt in this file he wants us to make: The following text should be placed in $HOME/.aksetup-defaults.py: BOOST_INC_DIR = ['/users/sfield/pool/include/boost-1_38/'] BOOST_LIB_DIR = ['/users/sfield/pool/lib'] BOOST_BINDINGS_INC_DIR = ['/users/sfield/pool/include/boost-numeric-bindings/'] BOOST_PYTHON_LIBNAME = ['boost_python-gcc41-mt'] BOOST_MPI_LIBNAME = ['boost_mpi-gcc41-mt'] # WITH_SPARSE_WRAPPERS = True Should I try to change the name to boost_python-gcc41-mt.so or boost_python-gcc41.a? I have all of these files in my boost library folder. These are the things I need to get installed: http://webapp.dam.brown.edu/wiki/SciComp/InstallHedgeFromGit http://documen.tician.de/pycuda/ I'm stuck and don't know what else to do....

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