December 2004 - Boost-users

Functors and function_traits<>
by Hossein Haeri 29 Dec '04

29 Dec '04

Dear all, Yep, again it's me, and it's agian function_traits<>... AFAIK, std::iterator_traits<> is one of the counterparts of function_traits<>, not? A sort of symmetry which iterator_traits<> has got is that it can work for Iterators as well as plain pointers. This seems to be not the case for function_traits<>. That is, you can pass a function type to it, but you can't do that for a functor. Is that right? If it is, a big drawback turns out to happen for variations of the following which are not that few common: template < typename ..., ..., typename Function > struct Foo { typedef typename function_traits<Function> ::result_type result_type; Foo (Function f) : f_(f) {} //... result_type operator () () {/*..*/} Function f_; }; This well works for sth like this: double f(double) {/*...*/} Foo<blah, ..., double (&) (double)> foo(f); But it does not work with the following: struct F { double operator () () {/*...*/} }; Foo f; Foo<blah, ..., F> foo(f); Is this what it should be? Or am I missing anything? In fact, the following code: struct F { double operator () (double x) const {return f(x);} }; typedef boost::function_traits<F>::result_type result_type; makes GCC 3.3.1 to give me an error like the previous one. This is what it says: Compiler: Default compiler Building Makefile: "C:\Documents and Settings\Hossein\My Documents\My Programmes\Probability I\Distributions\7.2.1\Makefile.win" Executing make... make.exe -f "C:\Documents and Settings\Hossein\My Documents\My Programmes\Probability I\Distributions\7.2.1\Makefile.win" all g++.exe -D__DEBUG__ -c 7_2_1Main.cpp -o 7_2_1Main.o -I"C:/Dev-Cpp/include/c++/3.3.1" -I"C:/Dev-Cpp/include/c++/3.3.1/mingw32" -I"C:/Dev-Cpp/include/c++/3.3.1/backward" -I"C:/Dev-Cpp/lib/gcc-lib/mingw32/3.3.1/include" -I"C:/Dev-Cpp/include" -pg -g3 7_2_1Main.cpp: In instantiation of `boost::function_traits<F>': 7_2_1Main.cpp:70: instantiated from `inverse_variate_generator<main()::Engine, main()::Distribution, F>' 7_2_1Main.cpp:106: instantiated from here 7_2_1Main.cpp:70: error: base class `boost::detail::function_traits_helper<F*>' has incomplete type 7_2_1Main.cpp: In instantiation of `inverse_variate_generator<main()::Engine, main()::Distribution, F>': 7_2_1Main.cpp:106: instantiated from here 7_2_1Main.cpp:70: error: no type named `result_type' in `struct boost::function_traits<F>' 7_2_1Main.cpp:76: error: no type named `result_type' in `struct boost::function_traits<F>' 7_2_1Main.cpp: In function `int main()': 7_2_1Main.cpp:113: error: no match for call to `( inverse_variate_generator<main()::Engine, main()::Distribution, F>) ()' 7_2_1Main.cpp:117: error: no match for call to `( inverse_variate_generator<main()::Engine, main()::Distribution, F>) ()' make.exe: *** [7_2_1Main.o] Error 1 Execution terminated What's wrong with it? Am I missing anything? If I'm not missing anything, then what is the work-around? I find myself right in expecting myself to be able to write a functor (like Foo) which can work equaly well with both function pointers and functors, as like as how the Standard algorithms do. Am I right? Or am I right? ;) TIA, --Hossein __________________________________ Do you Yahoo!? Take Yahoo! Mail with you! Get it on your mobile phone. http://mobile.yahoo.com/maildemo

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PROBLEM: How to determining the correct type to use at run time?
by Stephen torri 29 Dec '04

29 Dec '04

I want to expand the File_Base virtual interface here to allow me to pass the 'file_data' from the File class without have two sets of code: if (size == 32) 32 bite code else 64 bite code How do I expand the File_base interface? Is there a way to grab the type of a variable passed into a function and reuse it at run time? So that one time doSomething would have the following if the 'file_data' variable was passed in the File_Base interface: void doSomething (boost::shared_ptr<File_Base> const& f) { File<32> a = f->get_File(); // do 32 bit code } While another time the function code be: void doSomething (boost::shared_ptr<File_Base> const& f) { File<64> a = f->get_File(); // do 64 bit code } I would like to be generic so I don't have to repeat the same code. Stephen --------- SAMPLE PROGRAM -------- #include <iostream> #include <boost/shared_ptr.hpp> /*! \brief Type Mapper type */ template <int size> struct Type_Mapper; /*! \brief 32-bit Type Mapper */ template <> struct Type_Mapper<32> { /*! \brief 32-bit type */ typedef uint32_t arch_t; }; /*! \brief 64-bit Type Mapper */ template <> struct Type_Mapper<64> { /*! \brief 64-bit type */ typedef uint64_t arch_t; }; class File_Base { public: virtual uint32_t const get_Size() = 0; }; template <uint32_t size> class File : public File_Base { public: virtual uint32_t const get_Size() { return size; } typename Type_Mapper<size>::arch_t file_data; }; void doSomething (boost::shared_ptr<File_Base> const& f) { // Needs to access the variable 'file_data' in File<size> // Problem: How to expand File_Base interface so that // the variable 'file_data' can be returned without have // code like: if (f->get_Size() == 32) { // do 32 bit code } else { // do 64 bit code } } void create (void) { boost::shared_ptr<File_Base> f (new File<32>()); doSomething (f); } int main (int, char*) { create (); return 0; }

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[iostreams] New version available
by Jonathan Turkanis 29 Dec '04

29 Dec '04

Dear All, The latest version of the Iostreams library is now available: http://home.comcast.net/~jturkanis/iostreams/ I'd like to thank everyone who sent me bug reports after I posted the previous version. I will include you in the acknowledgments when I rewrite the documentation. Contents: - I. Changes - II. Supported platforms - III. Remaining bugs. ----- I. Changes. There are two important changes. First, the code conversion component has been renamed "code_converter", and it now has an optional Codecvt template parameter. Example. #include <boost/iostreams/code_converter.hpp> #include <boost/iostreams/device/mapped_file.hpp> // Perform code conversion using the global locale: typedef code_converter<mapped_file_source> wide_mapped_file_source; // Perform code conversion using utf8_codecvt_facet: typedef code_converter< mapped_file_source, utf8_codecvt_facet<wchar_t> > utf8_mapped_file_source; code_converter has now been tested with all the codecvt facets from the Dinkumware CoreX library. Second, there is now an option to build the libraries zlib and bzip2 from the source, rather than linking to a pre-built version. To build zlib from the source, define the following variables: ZLIB_SOURCE - path to the .co files ZLIB_INCLUDE - path to the .he files, if different from ZLIB_SOURCE To link to a pre-built version, define the following variables: ZLIB_INCLUDE - path to the .h files ZLIB_LIBPATH - path to the library or archive file ZLIB_BINARY - name of the library or archive file If ZLIB_LIBPATH is not defined, it is assumed that the library file is in a location where it will be found automatically. If ZLIB_BINARY is not defined, it defaults to "z" on UNIX and Cygwin, and to "zdll" on windows (see http://www.gzip.org/zlib/DLL_FAQ.txt) Similar remarks apply for bzip2. ----- II. Supported platforms The tests have been run on the following platforms: VC7.1 with Dinkumware GCC 3.2 (MinGW) GCC 3.4.2 (MinGW) GCC 3.4.1 (Cygwin) CodeWarrior 8.3 (static runtime only) Intel 7.1 with Dinkumware (static runtime only) Intel 8.0 with Dinkumware Borland 5.6.4 with STLPort Failures: - GCC (MinGW, Cygwin): wide streams not supported - Borland 5.6.4: undiagnosed runtime errors in seekable_file_test.cpp, direct_adapter_test.cpp and code_converter_test.cpp III. Remaining bugs. Although the bzip2 tests pass on all the platforms in II, there is an outstanding problem reported by Michel Decima which I haven't been able to fix yet. Best Regards, Jonathan

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Help requested: is_directory fails unexpected
by Tiziano Müller 28 Dec '04

28 Dec '04

Hi all I'm developing a little application (at the moment with VS.NET) using the boost::filesystem part to keep it portable. In the code I use the is_directory() function which fails unexpected when testing files with special characters ("little squares") in it. I tracked it down to the GetFileAttributesA-function which gives the error 123 ("The filename, directory name, or volume label syntax is incorrect."). After reading some pages in the internet, I assume that the only two solutions would be a) rename all those files first or b) make an own solution with the (unicode-enabled) function GetFileAttributesW which makes my app less portable (and will give me some headaches again). Is there a better solution? Thanks in advance, Tiziano

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function, bind & shared_ptr
by Roland Schwarz 28 Dec '04

28 Dec '04

I have found that it is bossible to create an in place functor like object by combining function, bind and shared_ptr. However altough it seems to work I am not sure whether this is safe usage. I would be glad if someone more knowledgeable had a look on it: class bar { void foo() { } }; boost::function<void ()> pfoo; int main(int argc, char* argv[]) { pfoo = boost::bind(&bar::foo, boost::shared_ptr<bar>(new bar)); pfoo(); // ... pfoo = 0; // this operation causes the ~bar dtor to be called return 0; } Thank you, Roland

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[MPL] transform and unpack_args
by David Greene 28 Dec '04

28 Dec '04

All right, I'm still trying to figure out the MPL lambda stuff. I had expected this to work: template<typename Arg> some func { typedef ... type; }; typedef transform< sequence, some_func<_> >::type result; But I get a compiler error about a missing apply<> in some_func. This works: typedef transform< sequence, quote1<some_func> >::type result; I don't understand why the placeholder doesn't convert some_func to an appropriate metafunction class. Similarly, I tried to use unpack args: template<typename Arg1, typename Arg2> some_func2 { typedef ... type; }; typedef transform< zipped_sequence, unpack_args<some_func2<_,_> >::type result; The compiler complained about a missing apply<> in some_func2. Again, this worked: typedef transform< zipped_sequence, unpack_args<quote2<some_func2> > >::type result; Is it because I'm using _ rather than _1 and _2? The examples in the MPL manual using is_same, etc. work fine for me. Learning lots. Hope to learn more. :) -Dave

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read_write_mutex asserting
by jkharris7＠comcast.net 27 Dec '04

27 Dec '04

Boost 1.32.0 on MSVC71 I have a test where I have one writer and five readers, each attempting the appropriate lock for their function on a read_write_mutex, and none doing it recursively. It keeps asserting on me like this: .....Assertion failed: ++loop_count == 1, file read_write_mutex.cpp, line 173 The above happens (in do_write_lock()) when I select reader_priority. Something similar happens in do_read_lock() when I select writer_priority. while (m_state == -1 || m_num_readers_to_wake == 0) { BOOST_ASSERT(++loop_count == 1); //Check for invalid loop conditions (but will also detect spurious wakeups) ++m_num_waiting_readers; m_waiting_readers.wait(l); --m_num_waiting_readers; } In release mode, it's fine, but what could be causing these "spurious wakeups"?

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Newbie Issues linking Boost Unit Test Framework
by Malloc 27 Dec '04

27 Dec '04

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 hey there... I recently downloaded, built, and installed Boost 1.32. I am attempting to use the Boost Unit Test Framework but am running into difficulties figuring out which lib to link to. I am compiling with MS VC++ 7.1. The headers appear to be discovered as they should be, but the linker is failing to find the correct lib. I have tried many of the libs which were created by the build, but these all create more errors (typically to do with redefinitions of std:: functions). At this point I am only trying to compile the example code supplied on the projects web site. some of the libs I tried: libboost_prg_exec_monitor-vc71-mt-1_32.lib libboost_test_exec_monitor-vc71-mt-1_32.lib libboost_unit_test_framework-vc71-mt-1_32.lib some articles I found online advised turning on mutithreading in the compiler properities, enabling run time type identification, and setting exceptions to /EHa I've done all of this but nothing is working, it really just looks like a linker problem. Thanks for any help Dave - ------------------------- linking errors: Linking... main.obj : error LNK2019: unresolved external symbol "bool __cdecl boost::test_tools::tt_detail::test_and_continue_impl(bool,class boost::basic_wrap_stringstream<char> &,class boost::unit_test::basic_cstring<char const >,unsigned int,bool,enum boost::unit_test::log_level)" (?test_and_continue_impl@tt_detail@test_tools@boost@@YA_N_NAAV?$basic_ wrap_stringstream@D@3@V?$basic_cstring@$$CBD@unit_test@3@I0W4log_level @63@@Z) referenced in function "void __cdecl free_test_function(void)" (?free_test_function@@YAXXZ) main.obj : error LNK2019: unresolved external symbol "public: void __thiscall boost::unit_test::test_suite::add(class boost::unit_test::test_case *,unsigned long,int)" (?add@test_suite@unit_test@boost@@QAEXPAVtest_case@23@KH@Z) referenced in function "class boost::unit_test::test_suite * __cdecl init_unit_test_suite(int,char * * const)" (?init_unit_test_suite@@YAPAVtest_suite@unit_test@boost@@HQAPAD@Z) main.obj : error LNK2019: unresolved external symbol "public: __thiscall boost::unit_test::test_suite::test_suite(class boost::unit_test::basic_cstring<char const >)" (??0test_suite@unit_test@boost@@QAE@V?$basic_cstring@$$CBD@12@@Z) referenced in function "class boost::unit_test::test_suite * __cdecl init_unit_test_suite(int,char * * const)" (?init_unit_test_suite@@YAPAVtest_suite@unit_test@boost@@HQAPAD@Z) main.obj : error LNK2019: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const & __cdecl boost::unit_test::ut_detail::normalize_test_case_name(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &)" (?normalize_test_case_name@ut_detail@unit_test@boost@@YAABV?$basic_str ing@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@AAV45@@Z) referenced in function "class boost::unit_test::test_case * __cdecl boost::unit_test::create_test_case(void (__cdecl*)(void),class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?create_test_case@unit_test@boost@@YAPAVtest_case@12@P6AXXZV?$basic_s tring@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) main.obj : error LNK2001: unresolved external symbol "public: virtual unsigned long __thiscall boost::unit_test::test_case::size(void)const " (?size@test_case@unit_test@boost@@UBEKXZ) main.obj : error LNK2019: unresolved external symbol "protected: __thiscall boost::unit_test::test_case::test_case(class boost::unit_test::basic_cstring<char const >,bool,unsigned long,bool)" (??0test_case@unit_test@boost@@IAE@V?$basic_cstring@$$CBD@12@_NK1@Z) referenced in function "public: __thiscall boost::unit_test::function_test_case::function_test_case(void (__cdecl*)(void),class boost::unit_test::basic_cstring<char const >)" (??0function_test_case@unit_test@boost@@QAE@P6AXXZV?$basic_cstring@$$C BD@12@@Z) libcpmtd.lib(xdebug.obj) : error LNK2019: unresolved external symbol __malloc_dbg referenced in function "void * __cdecl operator new(unsigned int,struct std::_DebugHeapTag_t const &,char *,int)" (??2@YAPAXIABU_DebugHeapTag_t@std@@PADH@Z) libcpmtd.lib(_tolower.obj) : error LNK2001: unresolved external symbol __malloc_dbg libcpmtd.lib(xdebug.obj) : error LNK2019: unresolved external symbol __free_dbg referenced in function "void __cdecl operator delete(void *,struct std::_DebugHeapTag_t const &,char *,int)" (??3@YAXPAXABU_DebugHeapTag_t@std@@PADH@Z) LIBCMT.lib(crt0.obj) : error LNK2019: unresolved external symbol _main referenced in function _mainCRTStartup Debug/unittests.exe : fatal error LNK1120: 9 unresolved externals Build Time 0:00 Build log was saved at "file://e:\C++Source\unittests\Debug\BuildLog.htm" unittests - 11 error(s), 0 warning(s) - ---------------------- Done ---------------------- Build: 0 succeeded, 1 failed, 0 skipped - ---------------------------------------------------------------------- - ---------- -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.3 for non-commercial use <http://www.pgp.com> iQA/AwUBQc8OX06myMoV5dC/EQL6eACeI7zolVzltRg/K4qyEtKtezJCVnkAmgK6 xSo1f992Mg3vXkIyQ/2Nk1z+ =6lrH -----END PGP SIGNATURE-----

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Problems with lexical_cast
by Georgios Diamantopoulos 27 Dec '04

27 Dec '04

Hello, I am trying to convert from wchar_t to std::string with #include <iostream> #include <sstream> #include <boost/lexical_cast.hpp> int main() { std::cout << boost::lexical_cast<std::string>(L"blah") << std::endl; return 0; } but I get the following error: d:\SDK\boost\include\boost-1_32\boost\lexical_cast.hpp(158) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::basic_stringstream<_Elem,_Traits,_Alloc>::_Mystr' (or there is no acceptable conversion) Any ideas? This is with boost 1.3.2 and VC7.1 Best regards, Georgios

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units library
by Chris Goller 26 Dec '04

26 Dec '04

I've been looking around for a unit conversion library. I've seen some on http://groups.yahoo.com/group/boost/files/ but am wondering if any have been put into boost release yet. Thanks, Chris

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