February 2007 - Boost-users

[signals] dropping ThreadingModel template parameter
by Frank Mori Hess 01 Mar '07

01 Mar '07

It seems that now that we drop locks before running slots, we can get by with using boost/detail/lightweight_mutex.hpp for our mutex. Since it is header-only, and apparently compiles to a null mutex if the compiler is in single-threaded mode, I don't see much need for a ThreadingModel template parameter on the signal class any more. I'm dropping it from thread_safe_signals. -- Frank

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boost::variant question
by Digvijoy Chatterjee 01 Mar '07

01 Mar '07

Hi, i have a boost::variant holding some C++ types which have to be inserted into the database : boost::variant<int, std::string, double > dbColumnValueVar; before i insert the value_type into the database I need to call a processing function which is overloaded for every datatype used in the variant ie. each of these functions are defined process ( int ); process ( std::string ); process ( double); template <class T> process(T); ..... what i do not understand is how do i use apply_visitor or some other tactic to automatically dispatch the call to the right process function as in : boost::variant<int, std::string, double > dbColumnVar; dbColumnVar = "hello world"; process ( dbColumnVar ); // should call process std::string ....but is always calling the generic template version ?? dbColumnVar = 1.3434; process ( dbColumnVar ); //again calls generic template not specialization cout << dbColumnVar is somehow able to get the correct overloaded << operator for the hidden datatype irrespective of datatype ?? Any help will be appreciated Thanks Digz

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[the Boost Graph library] no matching function : vertices(const Graph& g)
by Gerd Menche 01 Mar '07

01 Mar '07

Dear Boost users, I have come across this strange problem: After designing an interface to a library dealing with molecules (OpenBabel). I get the following compiler error: /usr/include/boost/graph/breadth_first_search.hpp: In function void boost::breadth_first_search(const VertexListGraph&, typename boost::graph_traits<G>::vertex_descriptor, Buffer&, BFSVisitor, ColorMap) [with VertexListGraph = OpenBabel::OBMol, Buffer = boost::queue<OpenBabel::OBAtom*, std::deque<OpenBabel::OBAtom*, std::allocator<OpenBabel::OBAtom*> > >, BFSVisitor = boost::VerboseBFSVisitor, ColorMap = std::vector<boost::default_color_type, std::allocator<boost::default_color_type> >]: bfs_example.cpp:73: instantiated from here /usr/include/boost/graph/breadth_first_search.hpp:96: error: no matching function for call to vertices(const OpenBabel::OBMol&) Easy enough you say -- go ahead and write that function. But it is allready in place. After modiying breath_first_search.hpp on line 96 from ... vertices(g) ... to ... gvertices(g) ... and changing the name of my vertices() function to gvertices(). It works. Is there a different vertices() function defined anywhere, that gets in the way? ____________________________________________________________________________________ Looking for earth-friendly autos? Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. http://autos.yahoo.com/green_center/

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boost 1.33.1 + qt 3.3.7 free on linux
by misiu 01 Mar '07

01 Mar '07

Hello, I'm developing standard c++ application with boost libs: any, thread, file_system, lambda, regex and everything is fine. Then I'm adding Qt for GUI and on MS Windows still fine but on Linux I got very strange problem: compilation and linking without problems (even no warnings) but just after start program hangs (even not showing GUI window) but not crushes (no core dumped). Without boost dependent parts Qt program works fine and boost parts without Qt work fine as well. What do you thing could make such a problem? What kind of checks can I do? If it is important I compiled Qt and boost by myself. I have to say I'm not so experienced with developing application on Linux, everything I'm preparing on Windows and from time to time I'm checking whether it works on Linux. Regards, Bartek

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[type_traits] is_function
by Cromwell Enage 28 Feb '07

28 Feb '07

Assuming a compiler supports is_function, will this metafunction check for the presence of member functions in a class? For example: struct Foo { void bar(); }; struct Baz { }; Given the right template argument, will is_function detect the bar() function in Foo but return false_ for Baz? If so, what is the right template argument? If not, are there any known workarounds? Cromwell D. Enage ____________________________________________________________________________________ Finding fabulous fares is fun. Let Yahoo! FareChase search your favorite travel sites to find flight and hotel bargains. http://farechase.yahoo.com/promo-generic-14795097

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[Boost-Users][serialization] Floating point precision
by jsanga＠cox.net 28 Feb '07

28 Feb '07

Is there a way to specify the precision of doubles when writing to xml_oarchive? Refer to the output snippet below. <Control class_id="3" tracking_level="0" version="1"> <Type>0</Type> <LowMZ>5.0499999999999998</LowMZ> <HiMZ>5.0999999999999996</HiMZ> I would like 5.05 and 5.1 for Low and High. Stepping through the code with the debugger I ended up in basic_text_oprimitive::save( const double t). void save(const double t) { if(os.fail()) boost::throw_exception(archive_exception(archive_exception::stream_error)); os << std::setprecision(std::numeric_limits<double>::digits10 + 2); os << t; } where it seems the precision is fixed. The only solution I can seem to think of is to split the serialization, and on the output convert my double to string (with the correct precsion) and then serialize the string. Is there a different or better way?

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[Boost.MultiIndex] Problem using dataelement from derived class as key
by Manuel Jung 28 Feb '07

28 Feb '07

Hi, Im having a problem. I derive class B from class A. class a has the member A::id. I want to use this one as key for my MultiIndexContainer. But i get the following compiling errors: test.cpp:41: Fehler: Templateargument »&A::id« konnte nicht in »unsigned int B::*« umgewandelt werden test.cpp:42: Fehler: Templateargument 2 ist ungültig test.cpp:43: Fehler: Templateargument 1 ist ungültig test.cpp:44: Fehler: Templateargument 2 ist ungültig Sorry it on german. A testfile for reproducing my problem is attached. Can someone help? thanks.. Greetings Manuel Jung

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[boost][circular_buffer] problem using copy contructor
by Andreas Rose 28 Feb '07

28 Feb '07

Hello, I'm new to circular_buffer. After reading the documentation i expect the following should work: const int c = 5; boost::circular_buffer<int> cb1(c); assert(cb1.capacity() == c); boost::circular_buffer<int> cb2(cb1); assert(cb2.capacity() == c); //failed, capacity() returns 0 But it does'nt work. After looking into the code of circular_buffer, i think the copy c'tor should be changed into something like this: circular_buffer(const circular_buffer<T, Alloc>& cb) : m_size(cb.size()), m_alloc(cb.get_allocator()) { initialize(cb.capacity()); BOOST_TRY { cb_details::uninitialized_copy(cb.begin(), cb.end(), m_buff, m_alloc); } BOOST_CATCH(...) { deallocate(m_buff, cb.capacity()); BOOST_RETHROW } BOOST_CATCH_END } Or do i missunderstand the documentation? I'm using vs2003 and the latest version of circular_buffer from boost-sandbox in ordinary debug mode. Thanks. Andreas Rose

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Problem using regex library in Windows/cygwin
by Diego Molla 28 Feb '07

28 Feb '07

Hi, I have a problem using the Boost regex library. I have isolated the problem to the attached piece of code. For some reason the output returned by the function that uses regex is garbage. I have tested the same program on a Linux version of boost and it works fine. I wonder if the problem is on the Windows installation. Could someone using Windows or Cygwin test this and tell me if it works? I've just re-installed the cygwin version (1.33.1-3) and I still get the same error. Here is a typical interaction. It should extract the XML attribute and value but instead it returns garbage: [diego@valencia ~...af/src]$ g++ -o regexError.exe regexError.cpp -lboost_regex-gcc-mt [diego@valencia ~...af/src]$ regexError Write a fragment of XML: this <test arg="a1">is a test</test> yeah Write the XML tag to search: test Found element is a test Searching arg="a1" Found attribute 1g with value a1 Write a fragment of XML: this <test a2="more">is another test</test> Write the XML tag to search: test Found element is another test Searching a2="more" Found attribute or with value morY Write a fragment of XML: end [diego@valencia ~...af/src]$ -- Do you want to know what is going on in Language Technology in Australia and New Zealand? Join ALTA -- http://www.alta.asn.au/ This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of Macquarie University. --------------------------------------------------------------------- Diego MOLLA ALIOD diego(a)ics.mq.edu.au Department of Computing http://www.ics.mq.edu.au/~diego Macquarie University

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[graph] patch to automatically build libbgl-viz.so and libbgl-viz.a
by David Baird 28 Feb '07

28 Feb '07

Hi, I'm interested in helping make the BGL easier to use right out-of-the-box. But, I'm not an expert at Boost (or Jamfiles) yet, so please guide me if this is wrong. I tried to patch the Jamfile so that it automatically builds the Graphgiz parser libraries (libbgl-viz.so and libbgl-viz.a). I only tested Jamfile (not Jamfile.v2) on some Gentoo boxes with gcc-4.1.1 and gcc-3.3.5 and it worked nicely. Some other future improvements I would like to do are to improve the Graphviz parser (to be able to parse more varieties of .dot files) and to review the documentation and check it for correctness (I already submitted some patches about half a year ago for a couple mistakes that I found). Please let me know what you think. Without further ado, here's the patch: Index: boost_1_33_1/libs/graph/build/Jamfile =================================================================== --- boost_1_33_1.orig/libs/graph/build/Jamfile +++ boost_1_33_1/libs/graph/build/Jamfile @@ -33,6 +33,21 @@ GRAPHVIZ_DEFS(graphviz_digraph_parser) = } local gGENERATOR_FUNCTION(LIB) = bgl-lib-file ; + dll bgl-viz + : ../src/$(SOURCES).cpp + : <sysinclude>$(BOOST_ROOT) <define>YY_NO_UNISTD_H + <runtime-link>dynamic + <define>BOOST_ALL_DYN_LINK=1 + # Darwin compiler ICEs if we turn optimization on + <darwin><*><debug-symbols>off + <darwin><*><optimization>off + # Intel compiler ICEs if we turn optimization on + <intel-win32><*><optimization>off + <vc-7_1><*><cxxflags>-GR- + : debug <inlining>on #inlining prevents linker name clashes due to truncation! + <debug-symbols>off # Debugging symbols become HUGE + ; + lib bgl-viz : ../src/$(SOURCES).cpp : <sysinclude>$(BOOST_ROOT) <define>YY_NO_UNISTD_H @@ -47,4 +62,7 @@ GRAPHVIZ_DEFS(graphviz_digraph_parser) = ; + install bgl-viz lib + : <dll>bgl-viz <lib>bgl-viz + ; } Index: boost_1_33_1/libs/graph/build/Jamfile.v2 =================================================================== --- boost_1_33_1.orig/libs/graph/build/Jamfile.v2 +++ boost_1_33_1/libs/graph/build/Jamfile.v2 @@ -24,3 +24,5 @@ obj graphviz_digraph_lex : graphviz_lex. <implicit-dependency>graphviz_digraph_parser ; obj graphviz_digraph_parser : graphviz_parser.yy : <bison.prefix>bgl_dir_ <define>GRAPHVIZ_DIRECTED=1 ; + +boost-install bgl-viz ;

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