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

Re: [Boost-users] program_options: wild write
by Merrill Cornish 27 Nov '05

27 Nov '05

Peter, Once I understood that even though positional parameters have been declared, they still have to be listed as an option, I got my positional parameter to work. I've even been able to follow the examples to "hide" the positional parameter name from the --help print out. I've still got the problem that an illegal option value triggers Dr Watson. I need to create a short example that I can post. Merrill

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How to sort a vector of tuples
by Sumanth J.V 26 Nov '05

26 Nov '05

Greetings, I have no idea why the following code does not work. Seems to work fine when I try sorting a vector of ints instead. I have even overloaded the < operator. If I understand correctly, this is the only requirement to sort a userdefined class. The compiler gets mad and spits out a a whole bunch of errors. thanx #include "boost/tuple/tuple_io.hpp" #include <vector> #include <algorithm> typedef boost::tuple<unsigned long int, unsigned long int, double, unsigned long int> Task; typedef std::vector<Task> TaskSet; bool operator<(const Task& a, const Task& b) { return boost::get<1>(a) < boost::get<1>(b); } int main(int argc, char** argv) { TaskSet ts; ts.push_back( boost::make_tuple(0, 0, 0, 0) ); ts.push_back( boost::make_tuple(3, 3, 3, 3) ); ts.push_back( boost::make_tuple(2, 2, 2, 2) ); std::sort(ts.begin(), ts.end()); return 0; }

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Re: [Boost-users] shared_ptr vs ordinary pointers
by Merrill Cornish 26 Nov '05

26 Nov '05

Jonathan, Yes, I should have left out the delete() for the shared_ptr version since that's one if its big features. I have used shared_ptr code similar to your example, but I can't use it in the case I'm thinking of. This particular pointer needs to be passed around so a single scope doesn't work. Thanks, Merrill

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shared_ptr vs ordinary pointers
by Merrill Cornish 26 Nov '05

26 Nov '05

With an ordinary C++ pointer, if I have a BaseClass and a DerivedClass derived from BaseClass, then I can do BaseClass* objectPtr; objectPtr = new DerivedClass(); Later, if BaseClass has a virtual destructor, I can call delete(objectPtr) and the DerivedClass destructor will be called. Now, does this work with shared_ptr? shared_ptr<BaseClass> objectPtr; objectPtr = shared_ptr<DerivedClass>(new DerivedClass()); and later, delete(objectPtr). Does any of the magic going on behind the scenes prevent shared_ptrs from being used like this? Merrill

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Re: [Boost-users] program_options: Failure Demo
by Merrill Cornish 25 Nov '05

25 Nov '05

Volodya, Should I post the ZIPs on boot-users or send it directly to you? Merrill

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Re: [Boost-users] program_options: Failure Demo
by Merrill Cornish 25 Nov '05

25 Nov '05

Volodya, I'm running Boost 1.33.0 compiled for MinGW multi-threaded. I agree that the message with only hex addesses isn't very useful, but that is all that pops up. ZoneAlert *says* the program is DWWIN.EXE, but I don't *see* Dr Watson. I disabled ZoneAlert and ran it again. I now have a 13KB Dr Watson log and a 3KB user.dmp file. Together, they ZIP to 4.8KB. Would you like me to send the ZIP to you? I have relinked the failing executable to remove unreferenced static libraries. It zips to 436KB. Would that be of any use to you? Merrill

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Question about boost::filesystem::path
by Stewart Tootill 25 Nov '05

25 Nov '05

I've just run into an interesting problem with boost::filesystem::path and thought I would raise it somewhere. When I run the following code, compiled with MSVC7.1, on windows XP I get an exception thrown when calling some_path_function. The exception is causes by boost::filesystem::path's implicit conversion constructor constructing a path from a string using the posix path matching rules. Obviously I can correct the problem by always using the native path checker argument, and that is fine, but the fact that this is an implicit conversion makes it hard to spot and I (and my colleagues) are not always that awake :). So I suppose the question is a) can the default path checking function be changed in such a way that on windows platforms it validates the path using windows rules and on posix platforms using posix rules, or b) should the constructor at fault here be made explicit since it can really catch you out. #include <boost/filesystem/path.hpp> #include <boost/filesystem/exception.hpp> #include <iostream> #include <string> void some_path_function( const boost::filesystem::path& path ) { std::cout << "Got a path : " << path.native_file_string() << std::endl; } int main() { try { std::string winPath = "c:\\windows\\system32\\kernel32.dll"; some_path_function( winPath ); } catch ( boost::filesystem::filesystem_error& err ) { std::cerr << "An error occured : " << err.what() << std::endl; } return 0; } Stewart Tootill Senior Engineer [Digital Text] Tel: +44 118 984 2151 - Fax: +44 118 984 3939 mailto:stewart.tootill@softel.co.uk www.softel.co.uk ________________________________________________________________________ This e-mail has been scanned for viruses by MessageLabs.

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program_options: Failure Demo
by Merrill Cornish 25 Nov '05

25 Nov '05

Below is a small program that demonstrates some of the problems I've been having. It takes one positional parameter, "limit" which is of type size_t. I'm linking statically with debug symbols. With the "try" in the position shown, after the declaration of vm, this is what happens to me for different command line arguments: * --limit=4 => works and prints limit=4 * --limt=4 => [notice misspelling] throws "unknown option limt" exception; but also triggers Dr. Watson: Application Error - The instruction at "0x0042eb49" referenced memory at "0x010900fb". The memory could not be "written". * --limit=-4 => [note negative value] never exits store(). Gets Dr. Watson "The instruction at "0x0049c090" referenced memory at "0x00eab651". The memory could not be "written. * --limit=xxx => [note string value] never exits store(). Get Dr. Watson with same message as above. Now, move the "try" to immediately after main() so all of the program options code is included in the try block. * --limit=4 => works as before * --limt=4 => [notice misspelling] Does NOT throw expected "unknown option" exception, never exits store(), but does trigger Dr. Watson, this time trying to read location 0xd. * --limit=-4 => similar error to above, with slightly different addresses. * --limt=xxx => similar error to above with slightly different addresses. Enjoy, Merrill //========================================== #include <iostream> #include "boost/program_options.hpp" using namespace std; namespace po = boost::program_options; int main(int argc, char* argv[]) { // try { po::options_description general("Option"); general.add_options() ("limit", po::value<size_t>()->default_value(1), " This is the concurrency limit."); po::variables_map vm; try { cout << "before store" << endl; po::store(po::command_line_parser(argc, argv). options(general).run(), vm); cout << "after store" << endl; po::notify(vm); if (vm.count("limit")) { cout << "limit=" << vm["limit"].as<size_t>() << endl; }//--version }//try catch (exception& e) { cerr << e.what() << endl; return 1; }//exception catch (...) { cerr << "unknown exception." << endl; return 1; }//... return 0; }//main() //=========================================

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Re: [Boost-users] Bind, lambda and how to chain relative function calls
by Kerner, Jacques 25 Nov '05

25 Nov '05

Erratum : Please replace ReturnArg by AdaptToReturningFunction in the AdaptToReturningFunction class definition. JK -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Kerner, Jacques Sent: Thursday, November 24, 2005 4:54 PM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Bind,lambda and how to chain relative function calls Hi, My example got a little bit more complicated. The Car::GetRigidBody function is : void Car::GetRigidBody(RigidBody & rb) instead of RigidBody & Car::GetRigidBody() So I have to write : bind ( &Position::GetX, bind ( &RigidBody::GetPosition, AdaptToReturningFunction<RigidBody>(bind(&Car::GetRigidBody, &car)) ) ) With a functor named AdaptToReturningFunction that transforms the first signature to the second : template<typename T> class AdaptToReturningFunction { public: ReturnArg(boost::function<void (T &)> f) : mF(f) {} T operator()() {T t; mF(t); return t;} private: boost::function<void (T &)> mF; }; Is there a simpler and better way of doing it without having to define AdaptToReturningFunction ? What if RigidBody was purely abstract (interface) ? Thank you. Jacques Kerner. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Peter Dimov Sent: Thursday, November 24, 2005 3:41 AM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Bind,lambda and how to chain relative function calls Kerner, Jacques wrote: > Hi, > > I would like to create a functor for calling functions in a chain like > this : > > car.GetRigidBody().GetPosition().GetX() > > What is the best way to do that using bind (and lambda ?) > > The car.GetRigidBody() is easy : bind(&Car::GetRigidBody, &car) , but > then I am a bit stuck. Note that I don't want to store the result of > car.GetRigidBody(). I want the final functor to call all the functions > everytime its operator() is called. So > > > bind ( > &Position::GetX, > &bind ( > &RigidBody::GetPosition, > &bind ( > > &Car::GetRigidBody, > &car > )() > )() > ) > > would not be acceptable... Just drop the invocations: bind ( &Position::GetX, bind ( &RigidBody::GetPosition, bind( &Car::GetRigidBody, &car) ) ) _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Re: [Boost-users] Bind, lambda and how to chain relative function calls
by Kerner, Jacques 25 Nov '05

25 Nov '05

Hi, My example got a little bit more complicated. The Car::GetRigidBody function is : void Car::GetRigidBody(RigidBody & rb) instead of RigidBody & Car::GetRigidBody() So I have to write : bind ( &Position::GetX, bind ( &RigidBody::GetPosition, AdaptToReturningFunction<RigidBody>(bind(&Car::GetRigidBody, &car)) ) ) With a functor named AdaptToReturningFunction that transforms the first signature to the second : template<typename T> class AdaptToReturningFunction { public: ReturnArg(boost::function<void (T &)> f) : mF(f) {} T operator()() {T t; mF(t); return t;} private: boost::function<void (T &)> mF; }; Is there a simpler and better way of doing it without having to define AdaptToReturningFunction ? What if RigidBody was purely abstract (interface) ? Thank you. Jacques Kerner. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Peter Dimov Sent: Thursday, November 24, 2005 3:41 AM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Bind,lambda and how to chain relative function calls Kerner, Jacques wrote: > Hi, > > I would like to create a functor for calling functions in a chain like > this : > > car.GetRigidBody().GetPosition().GetX() > > What is the best way to do that using bind (and lambda ?) > > The car.GetRigidBody() is easy : bind(&Car::GetRigidBody, &car) , but > then I am a bit stuck. Note that I don't want to store the result of > car.GetRigidBody(). I want the final functor to call all the functions > everytime its operator() is called. So > > > bind ( > &Position::GetX, > &bind ( > &RigidBody::GetPosition, > &bind ( > > &Car::GetRigidBody, > &car > )() > )() > ) > > would not be acceptable... Just drop the invocations: bind ( &Position::GetX, bind ( &RigidBody::GetPosition, bind( &Car::GetRigidBody, &car) ) ) _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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