October 2004 - Boost-users - lists.preview.boost.org

shared_ptr<> w/ Boost::Python
by John Meinel 30 Oct '04

30 Oct '04

I realize this may not be the right list, but since I'm already subscribed... I've been using boost::python to wrap some C++ code for quite a while now, and I've been quite happy with it. However, I decided to get into boost more, and I've found that shared_ptr/shared_array are quite nice. So I've started changing my functions from returning a raw pointer to returning a shared_ptr. In the boost::python tutorial, they talk about when you return a raw reference or pointer, you need to wrap it to manage lifetime of the object. http://www.boost.org/libs/python/doc/tutorial/doc/call_policies.html In the beginning of that page, they talk about how smart pointers are better for defining the scope and lifetime of objects, but sometimes raw pointers are necessary. I've gotten pretty good about when to manage_new_object, or return_internal_reference, etc. However, now that I have changed my return functions to actually return a smart pointer, it doesn't seem like I should need to wrap the return value anymore. Only now, when I try to do a "get" it gives me the error: " No to_python (by-value) converter found for C++ type: class boost::shared_ptr<class mine> " I have a converter for "class mine". I actually thought that the lifetime managers were using a shared_ptr, so if I did it myself, it would just be transparent. Does anyone know what the proper way to export a shared_ptr into python is? I suppose I could define the shared_ptr<class mine>, and only expose the "get()" function. But that would certainly be less than optimal. (I also obviously cannot wrap my function in another function that returns get(), because that would cause the shared_ptr to have the wrong lifetime.) Thanks for any help, John =:->

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RE: [Boost-users] i am stuck since a week here: need help:scopingerrorwhen trying to make boost work with luabind
by Brian Braatz 30 Oct '04

30 Oct '04

> help:scopingerrorwhen trying to make boost work with luabind > > Rohit O chokhani writes: > > Hi, i am a rookie as far as boost is concerned and i > > am trying to make boost work but just cant...on the > > point of giving up on it...so please help asap.... > > > > i am trying to use a scripting language called lua > > with my c++ source code. FOr that I felt the need to > > use luabind library which is completely dependent on > > boost.(project specific reasons for selecting luabind) > > > > > > As a result i need to have boost on my system. For the > > past 3-4 days ever since i have been trying to make > > boost works i have been getting all sorts of > > compilation errors. > > mainly they are as follows: > > > > C:\Program Files\Microsoft Visual > > Studio\VC98\INCLUDE\memory(16) : error C2059: syntax > > error : 'string' > > C:\Program Files\Microsoft Visual > > Studio\VC98\INCLUDE\memory(17) : error C2091: function [Brian Braatz] " C:\Program Files\Microsoft Visual > > Studio\VC98\" This shows me you are using VC6. While you "can" do this, you are asking for more pain than anyone should be forced to have. (it is not very compliant and has lots of template quirks. AND you get pages (and pages and pages and pages) of template warnings on valid code (making debugging compile time issues much more difficult) My *strong* suggestion to you is you install at least Visual Studio .net 2003 which comes with the vc++ 7.1 compiler. If you cannot purchase this product, the command line compiler is available for free download from: http://msdn.microsoft.com/visualc/vctoolkit2003/ Hope this helps (been there, done that, got the tee-shirt :) )

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RE: [Boost-users] shared_ptr<> w/ Boost::Python
by Nat Goodspeed 30 Oct '04

30 Oct '04

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of John Meinel > Sent: Saturday, October 30, 2004 9:24 AM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] shared_ptr<> w/ Boost::Python > > In the boost::python tutorial, they talk about when you return a raw > reference or pointer, you need to wrap it to manage lifetime of the > object. > http://www.boost.org/libs/python/doc/tutorial/doc/call_policies.html > > In the beginning of that page, they talk about how smart pointers are > better for defining the scope and lifetime of objects, but sometimes raw > pointers are necessary. I've gotten pretty good about when to > manage_new_object, or return_internal_reference, etc. > > However, now that I have changed my return functions to actually return > a smart pointer, it doesn't seem like I should need to wrap the return > value anymore. Only now, when I try to do a "get" it gives me the error: > > " No to_python (by-value) converter found for C++ type: class > boost::shared_ptr<class mine> " > > I have a converter for "class mine". I actually thought that the > lifetime managers were using a shared_ptr, so if I did it myself, it > would just be transparent. [Nat] We tell boost::python the smart pointer type we're using, like this: class_<DrawableInterface, DrawablePtr, boost::noncopyable> ("DrawableInterface", no_init) ; where DrawablePtr is a typedef for the smart pointer type.

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uBLAS bindings
by Daniel L Elliott 30 Oct '04

30 Oct '04

Hello, I would like to post this to uBLAS-users, but I am not yet a member. If anyone knows how to fix this, I would appreciate your help. I am working on adding identity matrices (and perhaps some others) to the gesv method of the LAPACK bindings. I have a couple questions about the code. In the template <typename MatrA, typename MatrB, typename IVec> inline int gesv (MatrA& a, IVec& ipiv, MatrB& b) method the static asserts are checking for the matrix types allowed within the gesv type? Instead of using gesv to invert a very large matrix (which would require us to create a very large identity matrix), would it be advisable to simply triangularize matrix A (maybe using LU) and use the uBLAS solver and an identity_matrix? Also, any overview of how the bindings and traits work would be very helpful! Thank you, Dan Elliott

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boost::function
by sboschi75-personal＠yahoo.it 30 Oct '04

30 Oct '04

Hallo, I would like to override operators for boost::function. Forexample I was thinking of an operator "-" : template <T> function<T> operator - (const function<T>& a) { // what do I write here in roder to return the symmetric function? } Thanks Stefano

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i am stuck since a week here: need help:scoping error when trying to make boost work with luabind
by Rohit O chokhani 30 Oct '04

30 Oct '04

Hi, i am a rookie as far as boost is concerned and i am trying to make boost work but just cant...on the point of giving up on it...so please help asap.... i am trying to use a scripting language called lua with my c++ source code. FOr that I felt the need to use luabind library which is completely dependent on boost.(project specific reasons for selecting luabind) As a result i need to have boost on my system. For the past 3-4 days ever since i have been trying to make boost works i have been getting all sorts of compilation errors. mainly they are as follows: C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\memory(16) : error C2059: syntax error : 'string' C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\memory(17) : error C2091: function returns function C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\memory(17) : error C2809: 'operator new' has no formal parameters C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\memory(20) : error C2954: template definitions cannot nest C:\BOOST2\BOOST\boost/mpl/aux_/integral_wrapper.hpp(88) : fatal error C1506: unrecoverable block scoping error Error executing cl.exe. i did find some solutions of the various forums of boost recommending to build the latest version from cvs in order to get rid of the scoping issue. however, that hasnt solved my case. could anyone kindly suggest some fixes, i would really appreciate it, thanks and regards, rohit __________________________________ Do you Yahoo!? Yahoo! Mail Address AutoComplete - You start. We finish. http://promotions.yahoo.com/new_mail

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RE: [Boost-users] Re: Boost work-in-progress list?
by Brian Braatz 29 Oct '04

29 Oct '04

> bounces(a)lists.boost.org] On Behalf Of Jeff Garland > > On Fri, 29 Oct 2004 11:10:11 -0600, Brian Braatz wrote > > That is an extremely good idea (putting up that Wiki). THANK YOU > > This point was discussed at the Boost/OOPSLA workshop held earlier in the > week. There was general agreement that we need to do a better job of > keeping > this list up to date and helping people find it. I'll be posting more > details > on the workshop results probably sometime next week. > > Jeff > > http://www.crystalclearsoftware.com/cgi- > bin/boost_wiki/wiki.pl?OOPSLA2004/Workshop > [Brian Braatz] Thanks Jeff. I missed the boost workshop as there were 2 tutorials given that my boss insisted I attend which conflicted. I will be very interested to read the notes from that workshop. ( I did stop by around 12:30 for Dave A's talk on Python, but noone was there- must have still been at lunch).. One question- What is the intended usage of the Wiki of things folks are working on for potential boost submission? I ask because I am preparing some info to send out to the list and basically in a spot where I will be one of those folks. (or maybe I should just wait patiently for your notes and all will be revealed ? :) )

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cross compile (ARM target)
by Josiah Bryan 29 Oct '04

29 Oct '04

Greets Boost users - I've just begun to play with boost for usage in a making my own GUI for my PDA (SimPAD), using AGG to render the widgets and Boost for the toolkit-type libraries (in place of the nice-but-GPLed Qt from trolltech). My question for you guys is this: 1) Is it possible to specify an abritray cross compiler for boost? - my build machine: Mandrake Linux 10.0 - cross compiler: gcc version 2.95.2 19991024 (release) - installed in /opt/Embedix/tools/bin/arm-linux-* 2) Is there already a predefined cross-compiler "target" for jam? Or maybe somebody understands what i need to do to get it crosscompiled, and can answer the question even if im not *asking* the right questions. :-) Any help is welcome.. Thanks! -- Josiah Bryan IT Coordinator Productive Concepts, Inc. jbryan(a)productiveconcepts.com (765) 964-6009, ext. 224

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RE: [Boost-users] gcc-3.4.1 and add_const
by Foster, Gareth 29 Oct '04

29 Oct '04

This randomly made me wonder ... if(const int * == int const *) Is that just a personal preference thing? Gaz -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Peter Dimov Sent: 26 October 2004 14:21 To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] gcc-3.4.1 and add_const Alexander Neubeck wrote: > Hi. > > I recognized a strange (wrong?) behaviour of gcc-3.4.1 (and > gcc-3.3.3). > When adding const to a type T and this type T is a reference, the > result is just T again (with reference, but witout const)! > Then I tested, if boost handles this case correctly, and it didn't. > The type of add_const< int & >::result is int & and not as expected > const int &. Your expectation was wrong. A "const" reference to int is not the same as a reference to a const int. [...] > My questions to you: > Can anybody verify this behaviour? > Is this behaviour intended? > If yes, WHY? Because that's how top-level const works. int * const != int const *, and int & const != int const &. > P.S: > It was quite difficult to check, which result-type the add_const > really created. First I used typeid( ... ).name(). But then I > recognized that int, int &, const int & produce ALL THE SAME name?!? Yes, that's how typeid works. _______________________________________________ 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] Re: Boost work-in-progress list?
by Brian Braatz 29 Oct '04

29 Oct '04

That is an extremely good idea (putting up that Wiki). THANK YOU > -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Aleksey Gurtovoy > > "Libraries Under Construction" page on the Boost Wiki > (http://www.crystalclearsoftware.com/cgi- > bin/boost_wiki/wiki.pl?LibrariesUnderConstruction) > is supposed to serve the purpose, but it's not up-to-date at the moment. > > You might consider posting a request for an update on this to the > developers list. > > HTH, > -- > Aleksey Gurtovoy

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