November 2007 - Boost-users

MPL Map of types to integral values
by Robert Dailey 17 Nov '07

17 Nov '07

Hi, I'm looking for a complete compile-time constant map container that uses types as keys and integral constants as values. For example: typedef map< pair<float, 90>, pair<unsigned int, 3> > mapType; unsigned int value = get_value<mapType, float>::value; The above code is PSEUDO CODE only. It is supposed to give you an idea of what I'm looking for. I tried using boost::fusion::map, however the fusion::pair object expects a TYPE as the second template argument, so I can't specify integral values. Could someone provide a code example that achieves the above? Note that I should be able to do the following as well: typedef map< pair<float, 90>, pair<unsigned int, 3> > mapType; class foo { // This would result in 'value' being the integral number 90. static const unsigned int value = get_value<mapType, float>::value; }

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some circular_buffer related question.
by Abir Basak 17 Nov '07

17 Nov '07

Respected Sir, I am using boost::circular_buffer in my program. It uses Visual Studio 7.1 . I am facing some problem related to iterator const correctness, where a nonconst iterator can't be converted to const iterator in release mode only (it works fine in debug mode) The program demosntrates it , #include <boost/circular_buffer.hpp> #include <boost/lambda/lambda.hpp> #include <iostream> int main(){ using namespace boost; using namespace boost::lambda; typedef circular_buffer<int> int_buf; int_buf buf(3); buf.push_back(1); buf.push_back(2); buf.push_back(3); buf.push_back(4); int_buf::const_iterator itb = buf.begin(); int_buf::const_iterator ite = buf.end(); std::for_each(itb,ite,std::cout<<_1<<"\t"); } It gives error in release mode of VS 7.1 as, e:\boost\trunk\boost\circular_buffer\details.hpp(262): error C2248: 'boost::cb_details::iterator<Buff,Traits>::m_buff' : cannot access private member declared in class 'boost::cb_details::iterator<Buff,Traits>' with [ Buff=boost::circular_buffer<int>, Traits=boost::cb_details::nonconst_traits<std::allocator<int>> ] and [ Buff=boost::circular_buffer<int>, Traits=boost::cb_details::nonconst_traits<std::allocator<int>> ] The boost version is latest boost svn trunk download. Apparently it seems, a friend declaration is missing, which causes the error in iterator to const iterator conversion through iterator(const nonconst_self& it) constructor conversion , where it tries to access it.m_it private variable. My second question is, is it valid to pass a const & a non const iterator to any function such as std::for_each, where both const iterators are required. If I pass such thing, it gives error as d:\Visual Studio Projects\Test\Test1.cpp(15): error C2782: '_Fn1 std::for_each(_InIt,_InIt,_Fn1)' : template parameter '_InIt' is ambiguous It it a valid error, or it is supposed to convert a non const iterator to const one, and match the template parameter, if it directly doesnt match anyone (as the conversion ctor is not explicit, I expect such automatic conversion is possible). thank you for such a fantastic library . -- Abir Basak, Member IEEE B. Tech , IIT KGP Technology Lead Software Engineer, Read Ink Technologies

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[boostbook] Building Boost documentation
by Edward Diener 17 Nov '07

17 Nov '07

Because I wanted to read documentation on some of the new libraries in the latest Boost SVN repository, which existed only in XML format, it was time to go through the annual rite of attempting to use Doug Gregor's excellent documention of "The Boostbook Documentation Format" in order to setup the documentation system to generate documentation using bjam. Although Mr. Gregor's documentation is extremely good, I have never been completely successful in the past, but I had my fingers crossed in hopeful expectation this time. I am doing this on Windows so I have to set things up manually. 1) I downloaded xsltproc and doxygen successfully, and "installed" them into appropriate directories and, to make things easy for myself, put those directories in my PATH. 2) After making sure I had no .jam file of any kind in my home directory I went to the \tools\build\v2\user-config,jam in the directory in which the latest Boost Subversion resides, and added the line: using xsltproc ; 3) I downloaded the latest XSL stylesheets and Docbook DTD and put them in their own separate directies, "E:\Utilities\docbook-xsl-1.73.2" and "E:\Utilities\docbook-dtd-4.2". 4) I added to my user-config.jam the lines: # BoostBook configuration using boostbook : E:/Utilities/docbook-xsl-1.73.2 : E:/Utilities/docbook-dtd-4.2 ; 5) Now further following instructions to test out my installation so far I went to the \libs\function\doc after copying boostbook.css from the \doc\html directory, and tried the bjam command. My result is: 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. Please refer to the Boost.Regex documentation for more information (don't panic: this is a strictly optional feature). E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/tools\boostbook.jam:300: in object(boostbook-generator)(a)326.run warning: rulename $(base-target).depends expands to empty string E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:840 : in try-one-generator-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:902 : in try-one-generator E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:111 0: in construct-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:118 6: in generators.construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1398: in construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1242: in object(typed-target)(a)327.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:765: i n generate-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:738: i n object(main-target)(a)331.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:255: i n object(project-target)(a)325.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2\build-system.jam:402: in load E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel\modules.jam:261: in import E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel/bootstrap.jam:132 : in boost-build E:\Programming\Version Control\Subversion\Boost\boost-build.jam:9: in module sco pe E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/tools\boostbook.jam:307: in object(boostbook-generator)(a)326.run warning: rulename $(target[2]).set-path expands to empty string E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:840 : in try-one-generator-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:902 : in try-one-generator E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:111 0: in construct-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:118 6: in generators.construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1398: in construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1242: in object(typed-target)(a)327.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:765: i n generate-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:738: i n object(main-target)(a)331.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:255: i n object(project-target)(a)325.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2\build-system.jam:402: in load E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel\modules.jam:261: in import E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel/bootstrap.jam:132 : in boost-build E:\Programming\Version Control\Subversion\Boost\boost-build.jam:9: in module sco pe E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/tools\boostbook.jam:308: in object(boostbook-generator)(a)326.run warning: rulename $(target[2]).depends expands to empty string E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:840 : in try-one-generator-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:902 : in try-one-generator E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:111 0: in construct-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\generators.jam:118 6: in generators.construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1398: in construct E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:1242: in object(typed-target)(a)327.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:765: i n generate-really E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:738: i n object(main-target)(a)331.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2/build\targets.jam:255: i n object(project-target)(a)325.generate E:/Utilities/BoostLibraries/boost_1_34_0/tools/build/v2\build-system.jam:402: in load E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel\modules.jam:261: in import E:\Utilities\BoostLibraries\boost_1_34_0\tools\build\v2/kernel/bootstrap.jam:132 : in boost-build E:\Programming\Version Control\Subversion\Boost\boost-build.jam:9: in module sco pe warn: Unable to construct ./function-doc ...found 1 target... 6) I have no doubt done something wrong, but I have no idea what. Anybody have any clues ?

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HOW TO: Building flexible structure definitions
by Robert Dailey 17 Nov '07

17 Nov '07

Hi, Right now I'm trying to develop a tricky structure that MAY contain any of the following information: - Vertex coordinates (x,y,z) - Color components (r, g, b) - Texture coordinates (u, v) Basically, I'd end up having a structure that looks like this (with all information included): struct Vertex { float x,y,z; // vertex coordinates unsigned char r, g, b; // color components double u,v; // texture coordinates }; The tricky part is that the user isn't required to create a structure with all of this information. For example, the structure above could be missing texture coordinates, color coordinates, or both (however the vertex coordinates are required since I doubt we care about empty structs)! This is for OpenGL vertex buffers, so in addition to this information we need to be able to specify some information in this structure that tells external classes a little bit more about itself. Note that this information CANNOT modify the size of the Vertex structure and must be compile-time only. For example: struct Vertex { // Information (does not change size). Note that if static const unsigned int vertex_type = GL_FLOAT; // Tells openGL the type of the x,y,z members static const unsigned int color_type = GL_UNSIGNED_CHAR; // Tells openGL the type of the r,g,b members static const unsigned int texture_type = GL_DOUBLE; // Tells openGl the type of the u,v members float x,y,z; // vertex coordinates unsigned char r, g, b; // color components double u,v; // texture coordinates }; But wait! There's more I need! This is the part that I was hoping boost could help me with. I have a class that takes objects of type Vertex (well, at least in this example it does. It takes a template argument. See below). The class needs a way (at runtime) to check of the Vertex object passed in has either color, texture, or vertex data in it. Example: template< typename t_vertex > class VertexBuffer { public: VertexBuffer( const t_vertex& vert ) { // How do I check what information is in vert? } } struct Vertex1 { float x,y,z; // vertex coordinates unsigned char r, g, b; // color components double u,v; // texture coordinates }; // This vertex type has NO color! // How would VertexBuffer tell?!? struct Vertex2 { float x,y,z; // vertex coordinates double u,v; // texture coordinates }; VertexBuffer<Vertex1> vbuffer1; VertexBuffer<Vertex2> vbuffer2; Is there something in boost I can utilize to make the definition of Vertex more flexible and open-ended? Perhaps I can use boost in the VertexBuffer class as well to determine the construct of the template type being passed in? Any and ALL help is appreciated.

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Problems with regex, using 1.34.1 version but asking for 1.31
by Arnau Rebassa 17 Nov '07

17 Nov '07

Hi all, I'm very newbie with boost and regex library. First I downloaded the latest version and compiled it for Visual Studio .NET 2003, the compilation went smooth but when I try to compile a minimal program it says: expressions_regulars fatal error LNK1104: cannot open file 'libboost_regex-vc71-sgd-1_31.lib'. I only have *1_34_1.lib files. Searching a bit more, I found the binary installer, so I removed everything from my manual compilation and installed it. When I try to compile, again the same message. I don't understand anything, any idea? Thanks to all!! -- Arnau _________________________________________________________________ Peek-a-boo FREE Tricks & Treats for You! http://www.reallivemoms.com?ocid=TXT_TAGHM&loc=us

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SORRY, FALSE ALARM ===> boost::type_traits::is_convertible.hpp ....how to assert a type is _not_ convertible?
by jono 17 Nov '07

17 Nov '07

i was misreading the error. it was my mistake. cheers jono''

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boost::type_traits::is_convertible.hpp ....how to assert a type is _not_ convertible?
by jono 17 Nov '07

17 Nov '07

hi all, i've got 2 classes like this.... //================================= struct Symbol : private std::string { public: Symbol(const char *cp):std::string(cp){} ~Symbol(){} }; struct String : private std::string { public: String(const String &s):std::string(s.c_str()){} String(const char *cp):std::string(cp){} ~String(){} }; //================================= // // and i'm trying to compile this.... // //================================= template<BinaryOp op, typename ObjectT> Object binary_op(const ObjectT &arg1, const ObjectT &arg2) { return undefined; } template<BinaryOp op> class BinaryOpVisitor : public boost::static_visitor<Object> { public: template<typename ObjectT, typename ObjectU> Object operator()( const ObjectT &arg0, const ObjectU &arg1) const { bool const y = boost::is_convertible<ObjectT, ObjectU>::value; return undefined; } template<typename ObjectT> Object operator ()(const ObjectT &arg0, const ObjectT &arg1) const { return binary_op<op, ObjectT>(arg0, arg1); } }; //================================= // // but using msvc 7.1 i'm getting the following error... // // s:\lib\boost_1_33_1\boost\type_traits\is_convertible.hpp(202) : // error C2243: 'type cast' : conversion from 'Symbol *__w64 ' to 'const std::basic_string<_Elem,_Traits,_Ax> &' exists, but is inaccessible // // //================================= // is_convertible.hpp(202) is as follows ... BOOST_STATIC_CONSTANT(bool, value = sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type) ); //================================= // // // how do i tell (deceive?) the compiler that the conversion does not exist? cheers, jono poff day-one digital auckland, nz

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[mpl] making an array of sizes given a type list
by Michael Marcin 16 Nov '07

16 Nov '07

Given a MPL Random Access Container (typename Types) I want to make a static const std::size_t array which contains the sizeof each type in Types. How can I do this? Thanks, Michael Marcin

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[regex] character classes when using wide chars
by Tomaž Šolc 16 Nov '07

16 Nov '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Documentation says that when using wide character strings with boost::wregex a character class like [[:alpha:]] depends on the system's implementation of iswalpha() function. My system seems to have a working implementation of iswalpha() function, but [[:alpha:]] still only seems to match ASCII alphabet characters. For example the following code: #define UNICODE #include <boost/regex.h> #include <stdio.h> #include <wctype.h> #include <locale.h> int main() { regex_t r; setlocale(LC_ALL, "en_US.utf8"); regcomp(&r, L"^[[:alpha:]]$", REG_EXTENDED); printf("%d\n", iswalpha(L'A')); printf("%d\n\n", regexec(&r, L"A", 0, NULL, 0)); printf("%d\n", iswalpha(L'\x160')); printf("%d\n\n", regexec(&r, L"\x160", 0, NULL, 0)); printf("%d\n", iswalpha(L'1')); printf("%d\n", regexec(&r, L"1", 0, NULL, 0)); regfree(&r); return 0; } Returns 1 0 1 1 0 1 In the second pair, iswalpha() correctly recognizes Unicode "S WITH CARON" character, however regular expression with [[:alpha:]] doesn't match it. I'm using Debian GNU/Linux with Boost 1.33.1. I also tried a similar program using boost::wregex and std::iswalpha() classes instead of the POSIX interface with the same results. Can anyone give me some advice on what I'm doing wrong here? Thanks Tomaž Šolc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHPNZXsAlAlRhL9q8RAlymAKDktxV+FWCTvBEBKwMNfr9yus5rgQCfc3N1 WoCdr+9zgBSEXPORSLAJiUM= =18dB -----END PGP SIGNATURE-----

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[condition] How to wait on multiple mutexes with OR semantics?
by Andrey Tcherepanov 16 Nov '07

16 Nov '07

Hello boosters, Let's say I have a 2 condition variables, and 2 threads that wait on them. I would like to collapse these 2 threads into 1 by making thread wait on *either* of these conditions to lock their mutexes (it is not the same mutex). Is it possible to do, or I better change the logic under the hood? Thank you very much, Andrey

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