Mailman 3 December 2008 - Cplusplus-sig

boost.python: implicit type conversion
by Mihail Konstantinov Dec. 2, 2008

Dec. 2, 2008

Dear all, thanks a lot for your immediate responses that lead to a fast solution for my previous problem. Here comes the next one. In the example below both classes A and B are derived from std::string. Class B can be implicitly converted to A by means of 'B::operator const A()'. So the function printme(const A&) can also be called with an argument of class B (see main function). My aim is to be able to call in python: >>>import boost_ext >>>b=boost_ext.B("hello world") >>>boost_ext.printme(b) but it produces the error: > <class 'Boost.Python.ArgumentError'>: Python argument types in boost_ext.printme(B) > did not match C++ signature: > printme(A) Can I modify the declaration inside BOOST_PYTHON_MODULE so that the implicit conversion is recognized and the above call boost_ext.printme(b) succeeds? Thank you Mihail BTW, in the code below I'm using a preprocessor definition __BJAM__ which I had to define explicitly in the Jamroot. Is there some variable defined by default which I can use to distinguish between bjam builds and other (testing) calls to g++? boost.cpp: #ifdef __BJAM__ // I define __BJAM__ in the Jamroot file.. #include <boost/python.hpp> #endif #include <string> #include <iostream> class A: public std::string{ public: A(const std::string&s,int i):std::string(s){} }; class B: public std::string{ public: B(const std::string&s):std::string(s){} operator const A(){return A(*this,-1);} }; void printme(const A &a){std::cout<<a<<std::endl;} int main(){ B b("hello world"); printme(b); } #ifdef __BJAM__ BOOST_PYTHON_MODULE(boost_ext) { using namespace boost::python; class_<std::string>("string"); class_<A,bases<std::string> > ("A",init<const std::string&,int>()); class_<B,bases<std::string> > ("B",init<const std::string&>()); def("printme",&printme); } #endif

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gccxml
by Alan Baljeu Dec. 2, 2008

Dec. 2, 2008

I'm lost getting the right gccxml for use with pygccxml. And of course that would be used in Pybindgen and/or py++. The links point to a gccxml page which advertises version 0.6, but docs talk about versions 0.7 and 0.9. Anyhow, I downloaded 0.6 and didn't have much success. But then I'm not sure what I'm supposed to do to get a proper scan. I also don't get where I would find 0.7 or 0.9 versions. Ideally I'd just like a documented package that gives me everything together that I can test out. Please advise. Alan Baljeu http://www.collaborative-systems.org Intelligent software that works _with_ you. __________________________________________________________________ Get the name you've always wanted @ymail.com or @rocketmail.com! Go to http://ca.promos.yahoo.com/jacko/

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boost.python: private copy constructor problem
by Mihail Konstantinov Dec. 2, 2008

Dec. 2, 2008

Hello, I am still in the early process of learning boost.python. I have reduced my problem to the following code: #include <boost/python.hpp> using namespace boost::python; class A{ private: A(const A&){}; //no public copy constructor }; class B: public A{ public: B(){}; }; BOOST_PYTHON_MODULE(boost_ext) { class_<A>("A",init<>()); class_<B, bases<A> >("B",init<>()); } When running bjam on this example, I get "boost.cpp:6: error: ‘A::A(const A&)’ is private" as the first error among a long list of hints from the compiler. How can I expose the classes with their constructors to python? Thank you Mihail

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shared_ptr with custom destructor
by Renato Araujo Dec. 1, 2008

Dec. 1, 2008

Hi all, I would like to specify during the class_ declaration use a shared_ptr with custom release function. shared_ptr has a constructor where you can pass a function to call in the release, I would like to use this in a generic form. I already tried some like that: shared_ptr<BaseClass> _custom_constructor() { return shared_ptr<BaseClass>(new BaseClass(), _release_func); } class_ <BaseClass, shared_ptr<BaseClass> > ("BaseClass").def("__init__", make_constructor(_custom_constructor)); but this not work to class derived from BaseClass: my _custom_constructor is not called to others class. I would like something more generic where I can declare in class_ template, something like that: class_<MyClass, boost::shared_ptr<MyClass, release_func> ("MyObject") ....... There is something like that? How is the best way to do this? BR -- Renato Araujo Oliveira Filho

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