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C# LINQ is cool. What about boost.qlang?
by Germán Diago 13 Oct '09

13 Oct '09

Hello. I've been reading a bit about C#'s linq and it's very cool in my opinion. I would like to see something similar in c++, and boost is the ideal place I think. As I would like to see something similar, I started a prototype adapted to c++. For now I've been playing with the basics: -from, where and select operators. -it just can be used (for now) with from, where and select, all in a row, but this will change. -it should work with any range: containers, boost.range, etc. -it's just a c++0x version. It works great with lambdas (gcc svn has lambdas). -Can use any boost.fusion sequence as the object type to query. (Although the plan is to be able to give data providers to use to query any type of source. The prototype works in the following way. For example (C++0x) : vector<int> numbers = {1, 2, 3, 4, 8, 5, 9 , 24, 19, 15, 12 } auto query = from(numbers).where([](int i) { return i < 15 && i > 10}). select(fields::full_object); This will construct an object with the query (without evaluating it). The original Range CANNOT be modified. If you want to modify , copy the result to a new container (in the future call query.to_vector(), query.to_list() to return a list or vector of objects. This will evaluate everything: for (auto it = query.begin(); it != query.end(); ++it) cout << *it << endl; You can traverse the range as many times as you like, and If you have, for example: struct Doctor { string name_; string surname_; string specializedin_; }; BOOST_FUSION_ADAPT_STRUCT(Doctor...) you can do, for example: vector<Doctor> doctors = {....}; auto query = from(doctors).where([](const Doctor & d) { return d.surname_ == "Smith"; }). select(fields::_1); The plan to improve readability is to use fusion associative sequence to do: auto query = from(doctors).where([](const Doctor & d) { return d.surname_ == "Smith"; }). select(Doctorfields::name, Doctorfields::specializedin); The query will return a tuple<string, string> in this case (the one before this would return tuple<string>. Queries with multiple fields don't work for now. A first implementation with the ability to select the full object or a field number (not several, but planned) is attached. Test it if you want and tell me what you think. The plan would be the same as the .NET platform: to be able to query XML, text files, objects, databases... giving extension points to add data providers. Another thing that doesn't work right now is to nest a query inside another query, but I'll work on it. Feedback is welcome.

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Re: [Boost-users] 1.40 and pch - gcc problems?
by Vial, Florent 13 Oct '09

13 Oct '09

Hi everyone, I downloaded and built bjam-3.17 under linux x86_64 (RHEL 4.6). I then built boost 1.40.0 using following command line: ../boost-jam-3.1.17/bin.linuxx86_64/bjam --build-dir=/tmp/build-boost-1_40_0 stage --build-type=complete --layout=tagged My user-config.jam has just been modified so that the toolset used is gcc4.2.3. I got following warnings in the math library: gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/release/l ink-static/assoc_laguerrel.o libs/math/build/../src/tr1/assoc_laguerrel.cpp:6:21: warning: /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/release/l ink-static/../src/tr1/pch.hpp.gch: created and used with different settings of -fpic gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/release/l ink-static/assoc_legendrel.o libs/math/build/../src/tr1/assoc_legendrel.cpp:6:21: warning: /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/release/l ink-static/../src/tr1/pch.hpp.gch: created and used with different settings of -fpic gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/release/l ink-static/betal.o [snip lots of them] Then the serialization library reports following warnings: gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/serialization/build/gcc-4.2.3/ release/link-static/xml_grammar.o In file included from ./boost/archive/impl/basic_xml_grammar.hpp:59, from libs/serialization/src/xml_grammar.cpp:16: ./boost/spirit/core/non_terminal/rule.hpp:18:4: warning: #warning "This header is deprecated. Please use: boost/spirit/include/classic_rule.hpp" In file included from libs/serialization/src/basic_xml_grammar.ipp:20, from libs/serialization/src/xml_grammar.cpp:63: ./boost/spirit/core/composite/operators.hpp:18:4: warning: #warning "This header is deprecated. Please use: boost/spirit/include/classic_operators.hpp" In file included from libs/serialization/src/basic_xml_grammar.ipp:21, from libs/serialization/src/xml_grammar.cpp:63: ./boost/spirit/core/composite/actions.hpp:18:4: warning: #warning "This header is deprecated. Please use: boost/spirit/include/classic_actions.hpp" In file included from libs/serialization/src/basic_xml_grammar.ipp:22, from libs/serialization/src/xml_grammar.cpp:63: ./boost/spirit/core/primitives/numerics.hpp:18:4: warning: #warning "This header is deprecated. Please use: boost/spirit/include/classic_numerics.hpp" gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/serialization/build/gcc-4.2.3/ release/link-static/xml_iarchive.o In file included from ./boost/archive/impl/basic_xml_grammar.hpp:59, from ./boost/archive/impl/xml_iarchive_impl.ipp:41, from libs/serialization/src/xml_iarchive.cpp:32: ./boost/spirit/core/non_terminal/rule.hpp:18:4: warning: #warning "This header is deprecated. Please use: boost/spirit/include/classic_rule.hpp" However, the build seems to go through. Then i do following: ../boost-jam-3.1.17/bin.linuxx86_64/bjam --build-dir=/tmp/build-boost-1_40_0 --build-type=complete --layout=tagged stage I then get following messages for the math library: gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/assoc_laguerre.o libs/math/build/../src/tr1/assoc_laguerre.cpp:6:21: warning: /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/../src/tr1/pch.hpp.gch: not used because `_REENTRANT' not defined gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/assoc_legendre.o libs/math/build/../src/tr1/assoc_legendre.cpp:6:21: warning: /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/../src/tr1/pch.hpp.gch: not used because `_REENTRANT' not defined gcc.compile.c++ /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/beta.o libs/math/build/../src/tr1/beta.cpp:6:21: warning: /tmp/build-boost-1_40_0/boost/bin.v2/libs/math/build/gcc-4.2.3/debug/lin k-static/runtime-link-static/../src/tr1/pch.hpp.gch: not used because `_REENTRANT' not defined [snip lots of them] I then type as root: ../boost-jam-3.1.17/bin.linuxx86_64/bjam install --prefix=/usr/local/boost1400-gcc423 And get following installation: [snip] common.copy /usr/local/boost1400-gcc423/lib/libboost_iostreams.a common.copy /usr/local/boost1400-gcc423/lib/libboost_math_tr1.a common.copy /usr/local/boost1400-gcc423/lib/libboost_math_tr1f.a common.copy /usr/local/boost1400-gcc423/lib/libboost_math_tr1l.a ...on 7500th target... common.copy /usr/local/boost1400-gcc423/lib/libboost_math_c99.a common.copy /usr/local/boost1400-gcc423/lib/libboost_math_c99f.a common.copy /usr/local/boost1400-gcc423/lib/libboost_math_c99l.a common.copy /usr/local/boost1400-gcc423/lib/libboost_program_options.a common.copy /usr/local/boost1400-gcc423/lib/libboost_python.a common.copy /usr/local/boost1400-gcc423/lib/libboost_serialization.a common.copy /usr/local/boost1400-gcc423/lib/libboost_wserialization.a common.copy /usr/local/boost1400-gcc423/lib/libboost_signals.a common.copy /usr/local/boost1400-gcc423/lib/libboost_prg_exec_monitor.a common.copy /usr/local/boost1400-gcc423/lib/libboost_unit_test_framework.a common.copy /usr/local/boost1400-gcc423/lib/libboost_thread.a common.copy /usr/local/boost1400-gcc423/lib/libboost_wave.a ...updated 7511 targets... However, for each library, i only have 2 files installed + 1 symbolic link: -rw-r--r-- 1 root root 148826 Oct 13 17:22 libboost_date_time.a lrwxrwxrwx 1 root root 28 Oct 13 17:22 libboost_date_time.so -> libboost_date_time.so.1.40.0 -rwxr-xr-x 1 root root 74552 Oct 13 17:22 libboost_date_time.so.1.40.0 Any idea what i might have done wrong ? (compiling under Win32/MSVC90 was no problem at all surprisingly) Thanks in advance, Florent ---------- Forwarded message ---------- From: "John Maddock" <j...(a)johnmaddock.co.uk> Date: 4 sep, 10:25 Subject: 1.40 and pch - gcc problems? To: BOOST Archives >I just got1.40and tried building. I kept having some pieces fail > with a complete build, sometimes I had gcc that ran until resources > exausted, sometimes the compiler would segfault. Eventaully I tracked > it down to the math library. After noticing the many errors from the > gch (things like : error _REENTERANT not defined or used diffrent > -fpic). I disabledpchfor the math library (actually the boost > project and the libs/math/test) and I did not have any more issues. Can you be more specific about the error messages? A: bjam --with-math will build just the math lib, if you could post the complete output that would be most helpful. There's something strange going on here though as it builds just fine locally here (ubuntu Linux), and on our regression test machines (various Linux flavours). Thanks, John. JOIN US FOR THE JOURNEY. View Our New Digital Cameras: www.arridigital.com Arnold & Richter Cine Technik GmbH & Co. Betriebs KG Sitz: Munchen - Registergericht: Amtsgericht Munchen - Handelsregisternummer: HRA 57918 Personlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH Sitz: Munchen - Registergericht: Amtsgericht Munchen - Handelsregisternummer: HRB 54477 Geschaftsfuhrer: Franz Kraus; Dr. Martin Prillmann

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[Property map] 1.40.0 breaks boost.graph python bindings
by John Reid 13 Oct '09

13 Oct '09

I'm using gcc 4.2.4 on Ubuntu. The boost.graph python bindings (http://www.osl.iu.edu/~dgregor/bgl-python/) work fine with boost 1.39. When I try with boost 1.40 I get many errors such as the following: ./boost/graph/python/resizable_property_map.hpp:101: error: ‘class boost::vector_property_map< boost::default_color_type, boost::graph::python::basic_index_map< boost::graph::python::basic_descriptor<boost::detail::edge_desc_impl<boost::bidirectional_tag, void *>, boost::bidirectionalS>, boost::adj_list_edge_property_map< boost::bidirectional_tag, long unsigned int, const long unsigned int &, void *, const boost::property<boost::edge_index_t, long unsigned int, boost::no_property>, boost ::edge_index_t>>>’ has no member named ‘get_store’ Does anyone know what changed between 1.39 and 1.40 to break this? The Readme.txt that comes with boost 1.40 suggests that nothing was updated in the property map library. BTW it doesn't compile with gcc 4.3 either but then neither does it compile with boost 1.39 (albeit for different reasons). I can provide all of the error messages if needed. John.

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Re: [Boost-users] [Boost.MPL]is it possible to generate types
by Tan, Tom (Shanghai) 13 Oct '09

13 Oct '09

Thanks, it works like a charm. Tan, Tom (Shanghai) wrote: > I have a templated class > > template<class U, class V, class W> > class S > { > //... implementations > }; > > and some stock type implementations for type U, V and W: > > typedef boost::mpl::vector<U0, U1> u_types; > typedef boost::mpl::vector<V0, V1, V2, V3, V4> u_types; > typedef boost::mpl::vector<W0, W1, W2, W3, W4> w_types; > > I want to test class S with all possible combinations of the template > arguments, > > typedef boost::mpl::vector< > S<U0,V0,W0>, > S<U0,V0,W1>, > // ... > S<U1,V4,W4>, > > s_types; > > like this: > boost::mpl::for_each<s_types>(test_func). > > The only problem is there are 2*5*5 = 50 combinations that I do not > wish to type in one by one. > > Is there a way to generate all the combinations with boost::mpl or > Boost.Preprocessor? >> Look at BOOST_PP_SEQ_FOR_EACH_PRODUCT In Christ, Steven Watanabe ***************************************

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Re: [Boost-users] Boost-users Digest, Vol 2134, Issue 4
by Tan, Tom (Shanghai) 13 Oct '09

13 Oct '09

Thanks, it works like a charm. Tan, Tom (Shanghai) wrote: > I have a templated class > > template<class U, class V, class W> > class S > { > //... implementations > }; > > and some stock type implementations for type U, V and W: > > typedef boost::mpl::vector<U0, U1> u_types; > typedef boost::mpl::vector<V0, V1, V2, V3, V4> u_types; > typedef boost::mpl::vector<W0, W1, W2, W3, W4> w_types; > > I want to test class S with all possible combinations of the template > arguments, > > typedef boost::mpl::vector< > S<U0,V0,W0>, > S<U0,V0,W1>, > // ... > S<U1,V4,W4>, > > s_types; > > like this: > boost::mpl::for_each<s_types>(test_func). > > The only problem is there are 2*5*5 = 50 combinations that I do not > wish to type in one by one. > > Is there a way to generate all the combinations with boost::mpl or > Boost.Preprocessor? >> Look at BOOST_PP_SEQ_FOR_EACH_PRODUCT In Christ, Steven Watanabe ***************************************

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[boost C++] algorithm for shortest path
by Boost lzw 13 Oct '09

13 Oct '09

Hi there, For the following unidirectional (one-direct only) pairs: A-B; G-H; B-D; D-G; H-K; K-D; The shortest path between A and D is: A-B-D, but none between A and H. Which Boost library should I use to develop such an algorithm or any hint on design it ? Thanks in advance. Robert

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Formal Review of Boost.Polygon extended one more week: until September 9, 2009
by Fernando Cacciola 13 Oct '09

13 Oct '09

Dear boost users, The review of Boost.Polygon was initially scheduled to end today. However, the discussions are in their best moment only now so the review period was extended by one week, until September 9, 2009 (that is next Wednesday). Best Fernando Cacciola Review Manager

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[python] Alternative to explicitly defining function pointers?
by Boris Schaeling 13 Oct '09

13 Oct '09

Is it possible to simplify this code without defining a function pointer? ----- struct X { void y(std::string) { } std::string y() { return ""; } }; std::string (X::*get_y)() = &X::y; class_<X>("X").add_property("y", get_y); ----- I tried to set the signature but if the documentation is right signatures only make sense for function objects - so this code doesn't work: class_<X>("X").add_property("y", make_function(&X::y, default_call_policies(), mpl::vector<std::string>())); Anything else Boost.Python offers to make adding properties even easier? If there is nothing I know at least that I didn't miss a shortcut and have to define function pointers myself. Boris

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[PREPROCESSOR] Working around the 256 element limit for sequences
by Rush Manbert 13 Oct '09

13 Oct '09

We define exception error codes and other useful information like this: #define EXCEPTION_TABLE \ ( (enumName0, "description string", "another sting", "yet another string") ) \ ( (enumName1, "description string", "another sting", "yet another string") ) \ . . . // End EXCEPTION_TABLE def Then we write a macro that creates an enum like this: #define ENUM_ERROR_CODES(EXCEPTION_TABLE_MACRO_NAME, firstErrorCodeValue)\ public: typedef enum \ { \ \ BOOST_PP_SEQ_FOR_EACH_I(MAKE_EXCEPTION_CODE_ENUM, ~, EXCEPTION_TABLE_MACRO_NAME) \ } ErrorCodesT; \ // End macro definition and we invoke ENUM_ERROR_CODES as: ENUM_EROR_CODEAS(EXCEPTION_TABLE, 1) This has worked just beautifully until recently. Now we're trying to use this code to define an enum (and other things) based on an EXCEPTION_TABLE that carries error code for a hardware device. There are about 500 of them. I ran into the 256 element limitation for sequences. I have tried rewriting the enum macro like this: #define ENUM_ERROR_CODES(EXCEPTION_TABLE_MACRO_NAME, firstErrorCodeValue)\ public: typedef enum \ { \ \ BOOST_PP_SEQ_FOR_EACH_I(MAKE_EXCEPTION_CODE_ENUM, ~, BOOST_PP_SEQ_SUBSEQ(EXCEPTION_TABLE_MACRO_NAME, 0, 250))\ BOOST_PP_SEQ_FOR_EACH_I(MAKE_EXCEPTION_CODE_ENUM, ~, BOOST_PP_SEQ_SUBSEQ(EXCEPTION_TABLE_MACRO_NAME, 250, 250))\ BOOST_PP_SEQ_FOR_EACH_I(MAKE_EXCEPTION_CODE_ENUM, ~, BOOST_PP_SEQ_SUBSEQ(EXCEPTION_TABLE_MACRO_NAME, 500, 250))\ BOOST_PP_SEQ_FOR_EACH_I(MAKE_EXCEPTION_CODE_ENUM, ~, BOOST_PP_SEQ_SUBSEQ(EXCEPTION_TABLE_MACRO_NAME, 750, 250))\ } ErrorCodesT; \ // End macro definition thinking that I could just peel off groups of 250, but that doesn't work. I can peel off the first N, where N is <= the size of the sequence, but I certainly can't do what I wrote. Each of our exception classes is defined this way, and the number of elements in each EXCEPTION_TABLE is different for each. Is there some standard method for working around this problem? Thanks, Rush

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exception error_info list?
by denis 12 Oct '09

12 Oct '09

Hi, what do you think about exposing the error_info-map of boost::exception? I would like to get all attached error infos from one exception. Then, everyone could implement his own version of diagnostic_information() without relying on boost internals. Beside that, I had another idea: When translating an exception it would be possible to copy all error_infos from the originating exception to the new one. How do you handle this loss of information at the time? thanks.

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