May 2005 - Boost-users - lists.preview.boost.org

enable_if< is_convertible > w/ explicit constructor trouble
by me22 14 May '05

14 May '05

After reading a recent Joel on Software article ( http://www.joelonsoftware.com/items/2003/10/13.html ) and the discussion it generated, I decided to try to write some sort of general strong typedef. I've started out by creating a specific class similar to what would be generated by a `typedef strong_typedef<tag,wrapped_type> name;`, and am trying to use enable_if and is_convertible to allow explicit construction from any type that can be converted to the wrapped type. Unfortunately, I keep getting errors such as the following: main.cpp:36: error: no matching function for call to `position::position(int)' main.cpp:7: error: candidates are: position::position(const position&) main.cpp:14: error: position::position() Compiler version: g++ (GCC) 3.3.5-20050130 (Gentoo Linux 3.3.5.20050130-r1, ssp-3.3.5.20050130-1, pie-8.7.7.1) Here's the cut down code. I'd greatly appreciate it if someone could point me towards what I'm doing wrong. Hopefully I'm just missing something elementary. ( I'm quite new to these boost features. ) On a side note, has anyone come up with a good method of wrapping these rather long SFINAE calls? Thanks, - Scott McMurray // begin code // #include <boost/type_traits.hpp> #include <boost/utility/enable_if.hpp> class position { public: typedef position my_type; typedef unsigned wrapped_type; private: wrapped_type m_data; public: position() {} // This works fine explicit position(boost::enable_if< boost::is_convertible<int, wrapped_type>, int>::type f) : m_data( f ) {} /* // But if I try this, I get the errors template <typename fT> explicit position(typename boost::enable_if< boost::is_convertible<fT, wrapped_type>, fT>::type f) : m_data( f ) {} */ }; int main(int argc, char* argv[]) { position x = position(5); } // end code //

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numeric_cast
by Marcin Kalici�ski 13 May '05

13 May '05

How do I make boost::numeric_cast work with a custom class? What templates do I need to specialize? converter? numeric_cast itself? The documentation is not quite clear about that, I have read it and studied the source code for some time, but found no clue. I think there should be a section about that in the docs. cheers, M.

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Serialization of cross-pointing objects
by Henrik Jacobsson 13 May '05

13 May '05

Hi! I want to serialize objects that link to each other through pointers, like a linked list, but in this case a more complex graph with several different classes and proxies (a graph which can contain loops and and null-pointers). But I get the "pointer conflict" exception since the serialization discovers that an object have been serialized once before through its pointer. The contents should be serialized/deserialized only once, and then the pointers should just be kept consistent. An alternative is of course to replace all the pointers with indeces which are memory-independent. But that's a messy affair. In the copy constructor I solved something similar through a map<Type*,Type*> which mapped from the old pointers to the newly allocated ones, so that they could be properly replaced. Is something like this hidden somewhere in the lib? Any suggestions? Best regards, Henrik Jacobsson

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RE: [Boost-users] what gets posted
by Marcin Tustin 13 May '05

13 May '05

I believe so. I never see messages I post, or at least I didn't until I went over to daily digests. > -----Original Message----- > From: Andreas Fabri [mailto:Andreas.Fabri@geometryfactory.com] > Sent: 13 May 2005 10:44 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] what gets posted > > > Hello, > > I recently posted a mail to the list, and got this mail from > boost-users-bounces(a)lists.boost.org > > ___________________________________________________________ > > Your message entitled > > BGL question: edge order > > was successfully received by the Boost-users mailing list. > > List info page: > http://lists.boost.org/mailman/listinfo.cgi/boost-users > Your preferences: > http://lists.boost.org/mailman/options.cgi/boost-users/andreas .fabri%40geometryfactory.com > > > ___________________________________________________________ > > > I find it in the archive, but I didn't receive it as mail. > Is this the policy of the list, that is I have to cc: it to myself? > > andreas > >

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program_options and ->notify(&your_function)
by Susan Flynn 13 May '05

13 May '05

Hi, I'm new to boost (and c++) and I've just started using program_options. Great concept and code, it has saved me a lot of time/effort, thanks. I am having a problem with the ->notify(&your_function) in add_options. I get a compile error (g++ on redhat): "invalid use of void expression". If I comment out the ->notify(&func) part, the code compiles. This is the code: void Report::PrintName(const string name) { cout << " the log name is " << name << "\n"; } void Report::InitCmdOpts(void) { try { p_opts = new po::options_description("Reporting"); p_opts->add_options() ("log", po::value< string >() ->default_value("sys.log") ->notify( &Report::PrintName)) ; } ...catch code... } Any help/ideas appreciated. I'm hoping it's something simple and my lack of c++ knowledge is showing. I've already simplified the code and tried several modifications, but the compile error persists. thanks, susan. __________________________________ Do you Yahoo!? Yahoo! Mail - You care about security. So do we. http://promotions.yahoo.com/new_mail

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what gets posted
by Andreas Fabri 13 May '05

13 May '05

Hello, I recently posted a mail to the list, and got this mail from boost-users-bounces(a)lists.boost.org ___________________________________________________________ Your message entitled BGL question: edge order was successfully received by the Boost-users mailing list. List info page: http://lists.boost.org/mailman/listinfo.cgi/boost-users Your preferences: http://lists.boost.org/mailman/options.cgi/boost-users/andreas.fabri%40geom… ___________________________________________________________ I find it in the archive, but I didn't receive it as mail. Is this the policy of the list, that is I have to cc: it to myself? andreas

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need help about wide character stream
by Tom Tan (SH/RDC) 13 May '05

13 May '05

hi,all i have 3 questions. 1. When i was trying wide character streams like wifstream ,wofstream , wcout etc. , i failed every time. My default locale is en_US.UTF-8. I created a test file , wrote a line Chinese "??" in that file. Then I try to use wifstream to read that file, after reading, i print it to stdout and write to another file. As a result , i got nothing. Assuming "input.txt" is the input file which contains Chinese character. BTW , input.txt is encoded with UTF-8. locale.global("en_US.UTF-8"); wifstream win("input.txt"); wcout<<win.rdbuf()<<endl; wofstream wout("output.txt"); wout<<win.rdbuf()<<endl; wout.close(); I got ouput: $ <nothing> $ wc -c outpu.txt $ 0 output.txt I am deeply puzzled, How does wide character stream works? 2. Can anybody explain why IBM ICU (International Component for Unicode) exists? What 's it for by comparing with stdc++ wide character mechanism? If it is necessary , is there any consideration to invent a similar package in BOOST? 3. Since my post looks more like a stdc++ question , anybody can tell me how i can join a stdc++ mail list? Thanks in advance. /Tom

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[iostreams] calling sink member function
by Daniel Schlyder 13 May '05

13 May '05

Hi, The following used to compile with MinGW GCC 3.4.2: <code> #include <boost/iostreams/concepts.hpp> #include <boost/iostreams/stream_facade.hpp> #include <iostream> class my_sink : public boost::iostreams::sink { public: std::streamsize write(char const *, std::streamsize size) { return size; } void foo() { std::cout << "foo() called" << std::endl; } }; int main() { boost::iostreams::stream_facade<my_sink> out; out->foo(); return 0; } </code> Now I get the following error: E:/libs/boost/boost/iostreams/stream_facade.hpp: In member function `my_sink * boost::iostreams::stream_facade<my_sink, char_traits<char> > ::operator->()': boost_iostreams_issues.cpp:36: instantiated from here E:/libs/boost/boost/iostreams/stream_facade.hpp:119: error: no match for 'operator *' in '*( ( ( boost::base_from_member< boost::iostreams::streambuf_facade< my_sink, char_traits<char>, boost::iostreams::output >, 0 > * )( (boost::iostreams::stream_facade<my_sink, char_traits<char> > * )this ) ) + 4u )->boost::base_from_member< boost::iostreams::streambuf_facade< my_sink, char_traits<char>, boost::iostreams::output >, 0 >::member' It compiles if I remove the call to foo(). What must I do to make it work again? Thanks, -- Daniel Schlyder http://bitblaze.com/

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RE: [Boost-users] Re: Question
by Sliwa, Przemyslaw (London) 12 May '05

12 May '05

Thanks for help, I have an additional question. Does anyone know why the following program gives different output on VC++ 6 and VC++ 2003 NET? It is pretty strange, isn't it? Thanks in advance. Pshemek #include <iostream> #include <cmath> using namespace std; class A { protected: char m_d; }; class B : public A { public: typedef char s; private: unsigned short g; }; class C : public A { public: typedef short unsigned s; private: unsigned d; }; template<bool cond> class Select {}; template<> class Select<true> { static void Statment1(double g) { cout << g*g << endl; } public: static void f(double g) { Statment1(g); } }; template<> class Select<false> { static void Statment2(double g) { cout << sqrt(g) << endl; } public: static void f(double g) { Statment2(g); } }; template<bool cond> void exec() { Select<cond>::f(3.0); } template<class T> void foo() { exec<sizeof(T::s)==sizeof(B::s)>(); exec<sizeof(T::s)==sizeof(C::s)>(); } int main() { foo<B>(); foo<C>(); return 0; } -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Eric Niebler Sent: 11 May 2005 18:37 To: boost-users(a)lists.boost.org Subject: [Boost-users] Re: Question Sliwa, Przemyslaw (London) wrote: > > I would like to write a template which depending on the argument type > does different things. > > For example the pseudo code: > > template <class T, class C> > foo(T& nT, C& nC) > { > // common code; > if(T==C) > // specific code; > ..... > > // again common code; > } > > Can the template meta programming help me in this case? It may. It depends on whether "specific code" compiles when T!=C. If it does, you could do this: template <class T, class C> void foo(T& nT, C& nC) { // common code if(boost::is_same<T,C>::value) { /* specific code */ } // again common code } where is is_same<> is defined in boost/type_traits/is_same.hpp. If "specific code" doesn't compile when T!=C, you need to get fancier. An overloaded helper function is the way to go: template<class T, class C> void specific_code(T&, C&) {} template<class T> void specific_code(T&, T&) { // specific code here } template <class T, class C> void foo(T& nT, C& nC) { // common code specific_code(nT, nC); // again common code } HTH, -- Eric Niebler Boost Consulting www.boost-consulting.com _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ --------------------------------------------------------

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Boost config compiler file for gcc 4.1
by Michael Hopkins 12 May '05

12 May '05

Hi all My first post to the list as a new Boost user. I'm sure there will be many more! Have just started to use GCC 4.1 tools and get this warning: In file included from /usr/local/include/boost/config.hpp:35, from /usr/local/include/boost/detail/iterator.hpp:53, from /usr/local/include/boost/array.hpp:32, from /home/mwh/Coding/C++/Headers/uo_container.hpp:15, from test2.cpp:16: /usr/local/include/boost/boost/config/compiler/gcc.hpp:92:7: warning: #warning "Unknown compiler version - please run the configure tests and report the results" So I was wondering, does a new config file /usr/local/include/boost/boost/config/compiler/gcc.hpp exist that deals with the latest GCC versions? I'm also not sure what the 'configure tests' are but I'm happy to run them if someone will point me to the relevant documentation. I'm on FreeBSD amd64 if that is of any use. TIA Michael P.S. Please cc repies to me if possible. _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ _/ _/ _/_/_/ Hopkins Research Ltd _/ _/ _/ _/ _/_/_/_/ _/_/_/ http://www.hopkins-research.com/ _/ _/ _/ _/ _/ _/ _/ _/ 'touch the future' _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

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