February 2007 - Boost-users

shared_ptr and RTTI
by Florin Trofin 27 Feb '07

27 Feb '07

Hello, A few years back, boost::shared_ptr did not require RTTI. I recently discovered that it does now. I understand that there are some benefits that RTTI brings to the new implementation, but I would have expected that there is some compile flag that can be turned on/off. Florin.

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[BGL] How to use an array in bundled property?
by Shufei Fan 27 Feb '07

27 Feb '07

I defined an double array inside bundled vertex property, and have trouble finding ways of accessing it. Neither can I find any where in the document an example on it. Your input will be much appreciated! my graph is defined as follows: struct Node{ // this is hard to access double mode[3]; }; struct Edge{ //no problem access them double nPixels; unsigned short nTh;}; typedef boost::adjacency_list< boost::vecS, boost::vecS, boost::bidirectionalS, Node, Edge> Graph; //Graph object colGraph Graph colGraph; I have no problem with accessing the 'nPixels' in Edge property, boost::property_map<Graph, double Edge::*>::type ew = get(&Edge::nPixels, *colGraph);//edge weight But I am in a great deal of trouble finding ways of accessing 'mode' in Node property. //compiler error here boost::property_map<Graph, double Node::*>::type nm = get(&Node::mode, *colGraph);//node modeerror message is : //---------------------------------------------------- c:\...\xxx.cpp(236) : error C2440: 'initializing' : cannot convert from 'boost::property_map<Graph,Property>::type' to 'boost::bundle_property_map<Graph,Descriptor,Bundle,T>' with [ Graph=boost::adjacency_list<boost::vecS,boost::vecS,boost::bidirectionalS,Node,Edge>, Property=double (Node::* )[3] ] and [ Graph=Graph, Descriptor=boost::property_map<Graph,double Node::* >::descriptor, Bundle=Node, T=double ] No constructor could take the source type, or constructor overload resolution was ambiguous//---------------------------------------------------- neither the following works(I added '[3]' in the parameter list): boost::property_map<Graph, double Node::*[3]>::type nm = get(&Node::mode, *colGraph);//node mode This time errors are raised in the 'property.hpp' file, they are: //---------------------------------------------------- c:\Boost\include\boost-1_33_1\boost\pending\property.hpp(40) : error C2825: 'PropertyTag::kind': cannot form a qualified name c:\Boost\include\boost-1_33_1\boost\graph\properties.hpp(198) : see reference to class template instantiation 'boost::property_kind<PropertyTag>' being compiled with [ PropertyTag=double Node::* [3] ] c:\shufei\VCProjects\edison\segm\GA.cpp(236) : see reference to class template instantiation 'boost::property_map<Graph,Property>' being compiled with [ Graph=Graph, Property=double Node::* [3] ]c:\Boost\include\boost-1_33_1\boost\pending\property.hpp(40) : error C2039: 'kind' : is not a member of 'operator``global namespace'''c:\Boost\include\boost-1_33_1\boost\pending\property.hpp(40) : error C2146: syntax error : missing ';' before identifier 'type'c:\Boost\include\boost-1_33_1\boost\pending\property.hpp(40) : error C2955: 'boost::type' : use of class template requires template argument list c:\Boost\include\boost-1_33_1\boost\type.hpp(14) : see declaration of 'boost::type'c:\Boost\include\boost-1_33_1\boost\pending\property.hpp(40) : fatal error C1903: unable to recover from previous error(s); stopping compilation//----------------------------------------------------thanks, _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=…

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faq How to compile graph?
by fcvcnet 27 Feb '07

27 Feb '07

Hi all, I know BGL just a few days. I need yours help. Now I only want to use the graph in the boost1.33.1 , how can I compile the only one component graph in vc6 or vs2005. So much thanks to your detail reply. Thanks again.

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[lambda] beginner's woes
by Imre Palik 27 Feb '07

27 Feb '07

Hi, I try to use boost::lambda in the following function: string build_headers(shared_ptr<connection> conn, vector<wstring> headers) { if (headers.empty()) return ""; return accumulate(++headers.begin(), headers.end(), string(1, '\'') + conn->quote(headers[0]) + '\'', (_1 + ", '" + bind(&connection::quote, var(conn), _2) + '\'')); } and wisual studio gives me the following error message error C2664: 'boost::lambda::bind' : cannot convert parameter 1 from 'overloaded-function' to 'SOCKET' 1> Context does not allow for disambiguation of overloaded function Could anybody help me decypher this message? What is this 'SOCKET' and how does it come into the picture? Thanks ImRe

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[signals] slot with no SlotFunction template parameter
by Frank Mori Hess 26 Feb '07

26 Feb '07

I'm implementing a more feature-full slot class with some of the things that have been discussed recently. In particular, it is templated only on signature. It uses a templated constructor to store the slot function in a pimpl object that is templated by both signature and slot function type. So now I'm about to rip out the SlotFunction parameter everywhere from thread_safe_signals, as there no longer seems to be any need for it. I feel like I might be overlooking something though. Is there any reason to keep it? -- Frank

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[signals] thread-safe post-disconnect() cleanup
by Frank Mori Hess 26 Feb '07

26 Feb '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 We could implement a thread-safe post-disconnect callback by using the existing tracking functionality. That is, the connection body could hold a "cleanup" shared_ptr with a custom deleter. The custom deleter would run the user's cleanup callback. A weak_ptr copy of the cleanup shared_ptr would be kept just like it was any other tracked object. When disconnect() is called, the cleanup shared_ptr would be reset. If the signal is being invoked concurrently when disconnect() is called, the cleanup code won't get run until the last invocation is done with the slot and destroys its copy of the cleanup shared_ptr. BTW, I've added support for a two-parameter version of signals::track() to thread_safe_signals/track.hpp. It seems to work okay, the only thing I don't like about it is it implies there a coupling required between the value and the tracked shared_ptr, when really there isn't. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFF3iTv5vihyNWuA4URAkzWAKDHL0MjcFGmAvKbWoBYmhNN5RiCMACgypCS SLJPrYcUaR0u4YTTS35lEZQ= =dCrK -----END PGP SIGNATURE-----

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Re: [Boost-users] [boost::any] - reference vs pointer
by Benjamin Winkler 26 Feb '07

26 Feb '07

References can not be copied. Thus, you can't make boost::any contain a reference (which is what mean when you write boost::any<double&>, I assume). In your example, msgargs.push_back(dref) calls the any-constructor any(const T&) with T being double, and this copies the value, not the reference itself. When you call msgargs.push_back(dptr), it calls the any(const T&) with T being double*. The value is copied again, only this time, the value is a pointer. Benjamin Winkler >Hi all, > >I've been trying out boost::any in a messaging system to package up function arguments. A message >call is basically > >Message::Call(std::vector<boost::any>& args) >{ >try >...a few any_cast<..> >...fire the actual function... >catch >...etc >} > >It's all good, except for one niggling problem. Say I have a double-precision value that I need >changed inside the message, so it needs to be passed as a double* or a double& in an argument. The >problem is, if I create a double& inside a boost::any, it doesn't point to the right memory location >once I'm inside the message, and it looks like it's copying the original dereferenced value and >giving me a reference to the copy. If I create a double* inside a boost::any, I get a new pointer >inside the message like the reference, but because the pointer target is correct everything works. >The code looks like this: > >... >... >std::vector<boost::any> args; >double d = 1.5; >double* dptr = &d; >msgargs.push_back(dptr);//works fine... >double& dref = d; >msgargs.push_back(dref);//seems to copy d instead of a reference to d... >... >msg->Call(args); >... > >I can live with this, I just have to pass "large" objects by pointer so they don't get copied. BUT: > Can anyone tell me why references are creating a copy of the original and not a copy of the >reference, or how I could avoid the copying? Or am I doing something dumb? > >Damien >_______________________________________________ >Boost-users mailing list >Boost-users(a)lists.boost.org >http://lists.boost.org/mailman/listinfo.cgi/boost-users >

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[FileSystem] Getting modified date and time from a file?
by Lawrence Spector 26 Feb '07

26 Feb '07

Does boost provide a portable way to do this? I didn't see an obvious way; I was hoping others might have ideas. Thanks in advance, Lawrence

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[program_options] Documentation of configuration file format?
by Tarjei Knapstad 26 Feb '07

26 Feb '07

I can't seem to find any documentation on what kind of file formats are accepted when calling boost::program_options::parse_config_file(...) Am is missing it or is it missing? :) -- Tarjei

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BoostCon'07 Registration Now Open
by info＠boostcon.com 26 Feb '07

26 Feb '07

The following message is a courtesy copy of an article that has been posted to comp.lang.c++.moderated,comp.std.c++,comp.lang.c++ as well. I'm pleased to announce that the official website for the inaugural Boost conference is up and registration is open: http://www.boostcon.com Due to the very high quality of the submissions we've received, our program committee has been able to assemble a lineup of speakers and topics the likes of which I haven't seen anywhere (http://www.boostcon.com/program) Combine that with the relaxed atmosphere of the conference venue (http://www.boostcon.com/location) and I think we can all look forward to a truly unique and memorable week of working and learning together. I invite you to visit http://www.boostcon.com/registration to register. -- Dave Abrahams Boost Consulting www.boost-consulting.com

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