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Global mutex and boost.thread
by Daher 19 Sep '06

19 Sep '06

I need to perform disk activity to a shared file across multiple instances of my program... my program was originally written using windows API and I'm porting it to other systems. and I'm using boost.thread for my threads.. Any way to create a global mutex? on windows all you need to do is provide "Global\" Prefix to the mutex name. Any ideas will be appreciated. Thanks in advanced. Dee

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converting value before inserting into a list
by Alexander Shyrokov 19 Sep '06

19 Sep '06

I want to convert values according to a map before inserting it into the list. What is a proper way to do that? I have this: map<int,int> m; vector<int> a,b; for(vector<int>const_iterator i=a.begin();i!=a.end();++i) b.push_back(m[*i]); I could use std::copy with std::back_inserter to add elements to b, but how do I convert it first? Should I write my own version of back_inserter for that? copy(a.begin(),a.end(),my_back_inserter(b,m)); Thanks. -- Regards, Alexander. http://sjcomp.com

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Re: [Boost-users] converting value before inserting into a list
by Hughes, James 19 Sep '06

19 Sep '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > Alexander Shyrokov > Sent: 19 September 2006 14:19 > To: boost-users(a)lists.boost.org > Subject: [Boost-users] converting value before inserting into a list > > I want to convert values according to a map before inserting > it into the list. What is a proper way to do that? > I have this: > > map<int,int> m; > vector<int> a,b; > > for(vector<int>const_iterator i=a.begin();i!=a.end();++i) > b.push_back(m[*i]); > > I could use std::copy with std::back_inserter to add elements > to b, but how do I convert it first? Should I write my own > version of back_inserter for that? > > copy(a.begin(),a.end(),my_back_inserter(b,m)); > > Thanks. > -- > Regards, > Alexander. http://sjcomp.com > _______________________________________________ I probably being very anti-modern C++ here, but I think that the for loop takes a lot of beating for readability......its probably the most efficient too (with a bit of cacheing of invarients)...... I do find that some of these so called 'helpers' do make the code more obscure, but that's perhaps because I have spent 15 years doing C then C++, rather than solely starting with C++. James > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users > This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.

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Re: [Boost-users] [serialization] Purpose of load_construct_data (was: Re: Library Interface Design)
by JOAQUIN LOPEZ MU?Z 19 Sep '06

19 Sep '06

Hello Robert, ----- Mensaje original ----- De: Robert Ramey <ramey(a)rrsd.com> Fecha: Sábado, Septiembre 16, 2006 9:00 am Asunto: Re: [Boost-users] [serialization] Purpose of load_construct_data (was: Re: Library Interface Design) > > I am not sure. I'm a little puzzled about the intended purpose of > > load_construct_data, as the docs and the code of Boost.Serialization > > seem to suggest that it is used for two incompatible tasks: > > > > a) to construct a dummy object prior to deserialization itself, thus > > providing a user-overridable hook in case default construction > is not > > appropriate. > > b) to deserialize in place as explained on the bit you quote. > > > > The intended purpose was to address de-serialization of objects > that have no default constructor. See test_non_default_ctor. > > > My hunch is that Robert started this with b) in mind but finally the > > facility was kept playing a more humble role as a). Consider for > > instance, serialization of pointers: currently, if an object > instance> is saved exclusively through pointers, > Boost.Serialization does the > > following when the first such > > pointer is met > > > > save_construct_data(ar,p); // S(0) > > ar<<*p; // S(1) > > > > and correspondingly at loading time > > > > p=get unitialized storage; > > load_construct_data(ar,p); // L(0) > > ar>>*p; // L(1) > > > > By default save_construct_data does nothing and load_construct_data > > creates a default cted object, effectively leading to a two-phase > > construction scenario. Now, if the user decides to override > > (save|load)_construct_data > > for some class, say foo, so as to perform one-phase construction, > > we've got the following: > > > > S(0) saves foo contents > > S(1) saves foo contents again > > Nope. save_construct_data saves ONLY that data needed for > constructionwhile ar << *p save that data NOT used in construction. > > > L(0) loads foo contents and creates a foo object with these. > > L(1) loads foo contents again > > Nope - see above. > > I believe this is well illustrated by the > test_non_default_ctor.cpp example > previously cited. > > Note that in generally, the data required to construct an instance > might not > be part of the instance itself. This is also addressed by this api. > > I'm not sure, but I suspect this could be also useful in de- > serializationof objects which contain references to other objects > as references can > only be set at object construction time. Tracking would still work. > Thanks for pointing me to test_non_default_ctor.cpp. I think this example nicely illustrates the purposes which (load|save)_construct_data is meant to serve, and that you've summarized in your comments above: * handle types without a default ctor. * serialize data used at construction time which are *not* serialized by T::serialize. and this is all good, but if I'm understanding you right then you're stating (in agreement with my analysis) that (load|save)_construct_data can't be used for one-phase serialization, and that two phases (construction and serialization) are still needed. The original post by Dave said otherwise, though, and I think the misunderstanding comes from the example at http://boost.org/libs/serialization/doc/serialization.html#constructors where my_class serializes my_class::m *both* at my_class::serialize *and* my_class::(load|save)_construct_data. If the analysis I develop in my previous post is correct (is it?) this leads to my_class::m being serialized *twice* when a pointer to my_class is saved. Maybe it would sufice to rewrite this part of the documentation with a more sensible example like the one at test_non_default_ctor.cpp. What do you think? > Robert Ramey Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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In reply to: " edge function"
by Tom Lenaerts 19 Sep '06

19 Sep '06

Hi stephan, sorry about the lack of detail in my question. Below you can find the code for a network factory class. The code reads a file (like this) 300 0 37 0 1 2 3 4 5 6 8 9 15 17 21 42 44 51 56 63 66 77 84 86 93 123 126 128 129 151 153 163 164 170 219 225 240 247 261 288 290 1 12 0 0 2 11 18 33 47 66 95 127 192 209 211 2 51 0 1 0 3 5 6 7 8 10 12 13 14 15 16 17 19 25 27 31 35 36 38 49 78 79 81 84 88 91 93 104 111 139 156 169 175 178 188 203 208 223 227 243 247 249 253 255 266 267 268 282 286 3 8 0 2 0 4 29 42 55 62 257 4 11 0 3 0 18 34 52 59 108 139 216 235 296 5 14 0 2 0 26 50 56 58 71 74 80 186 191 193 194 283 6 14 0 0 2 7 16 30 34 46 57 101 141 174 198 215 291 7 6 0 2 6 67 82 97 181 ... and when the member function 'create' is called, the network should be returned. The error was a runtime error. I got the following answer from Xcode: [Session started at 2006-09-19 09:57:00 +0200.] #seed.in not found. Creating a new seed... seed = 583597 gamenetwork has exited due to signal 10 (SIGBUS). I examined your code and adapted mine to yours and noticed that the error disappears when I change g=new Graph(); to g=new Graph(1); in the member function parseFile. It seems that this is the error that I made (as I expected it is a silly one). Could you tell me why the '1' is required here? Thanks for the help Tom ==networkfact.h #ifndef __NETWORKFACTORY_H #define __NETWORKFACTORY_H #include "factory.h" #include <boost/graph/adjacency_list.hpp> #include <boost/graph/graph_traits.hpp> using namespace std; typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS> Graph; typedef Graph* Graphptr; typedef boost::graph_traits<Graph>::edge_descriptor Edge; typedef boost::graph_traits<Graph>::vertex_descriptor Vertex; typedef boost::graph_traits<Graph>::vertex_iterator Vertex_iterator; typedef boost::graph_traits<Graph>::edge_iterator Edge_iterator; typedef boost::graph_traits<Graph>::vertices_size_type Vertex_type; typedef boost::property_map<Graph, boost::vertex_index_t>::type IndexMap; typedef Factory<Graph> GraphFactory; // the factory creates new graph instances class NetworkFactory: public GraphFactory { public: NetworkFactory(string fname): _fname(fname){}; //the file contains a grpah specification. ~NetworkFactory(){}; Graphptr create(); private: Graphptr parseFile(istream&); void tokenize(const string&, vector<string>&, const string& delimiters = " "); void processTokens(vector<string>&, Graphptr); string _fname; }; typedef NetworkFactory* NetworkFactoryptr; #endif ==networkfact.cpp #include "networkfact.h" #include <boost/lexical_cast.hpp> #include <sstream> #include <fstream> Graphptr NetworkFactory::parseFile(istream& is){ char c; int numnodes=0; Graphptr g=NULL; while(!is.eof()){ c=is.get(); if(c=='#' || c == '\n'|| c == ' '){ string line; getline(is,line,'\n'); //ignore line content } else{ //it is not a comment line but useful information. is.putback(c); string line; getline(is,line,'\n'); //start parsing the line vector<string> tokens; tokenize(line,tokens); if(tokens.size() == 1){ numnodes= boost::lexical_cast<int>(tokens[0]); g=new Graph(1); } else { if(g!=NULL) processTokens(tokens,g); } } } return g; } void NetworkFactory::tokenize(const string& str, vector<string>& tokens, const string& delimiters){ // Skip delimiters at beginning. string::size_type lastPos = str.find_first_not_of(delimiters, 0); // Find first "non-delimiter". string::size_type pos = str.find_first_of(delimiters, lastPos); while (string::npos != pos || string::npos != lastPos) { // Found a token, add it to the vector. tokens.push_back(str.substr(lastPos, pos - lastPos)); // Skip delimiters. Note the "not_of" lastPos = str.find_first_not_of(delimiters, pos); // Find next "non-delimiter" pos = str.find_first_of(delimiters, lastPos); } } void NetworkFactory::processTokens(vector<string>& tokens, Graphptr g){ if(tokens.size()>=3){ int current = boost::lexical_cast<int>(tokens[0]); int numedges = boost::lexical_cast<int>(tokens[1]); Vertex first=boost::vertex(current,*g); for(int i=0;i<numedges;i++){ int other= boost::lexical_cast<int>(tokens[3+i]); //this has to be 3 because some other data is in position 2 Vertex second=boost::vertex(other,*g); pair<Edge, bool> result=boost::edge(first,second,*g); if(!result.second){ boost::add_edge(first,second,*g); } } } } Graphptr NetworkFactory::create(){ ifstream netwfile(_fname.c_str()); if(netwfile.is_open()){ Graphptr res= parseFile(netwfile); netwfile.close(); return res; } return NULL; }

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BOOST_FOREACH and maps
by Rob Caldecott 18 Sep '06

18 Sep '06

OK, I know BOOST_FOREACH isn't part of the official (1.33.1) build yet, but hopefully some people here are using this excellent algorithm and can help me out... (note that I am using MS Visual Studio 2005): How can I use BOOST_FOREACH to iterate through a map? For example, the following won't build: std::map<int, int> m; BOOST_FOREACH(std::pair<int, int> p, m) { } I get the following error: warning C4002: too many actual parameters for macro 'BOOST_FOREACH' However, the following will work OK: std::map<int, int> m; std::pair<int, int> p; BOOST_FOREACH(p, m) { } But is there a way to declare the pair within the FOREACH loop? Note that I also tried the following, with no success: std::map<int, int> m; BOOST_FOREACH(std::map<int, int>::value_type p, m) { } A typedef also seems to work, e.g.: std::map<int, int> m; typedef std::pair<int, int> mpair; BOOST_FOREACH(mpair p, m) { } Can the pair be declared without a typedef? Is this a limitation of the MS compiler? Thanks in advance.

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edge function
by Tom Lenaerts 18 Sep '06

18 Sep '06

This is again a newbie question. I want to create a graph based on some input file. I parse this file and in the code I want to check whether the link already exists int current=strToInt(tokens[0]); int numedges=strToInt(tokens[1]); for(int i=0;i<numedges;i++){ Vertex first=vertex(current,*g); int other=strToInt(tokens[3+i]); Vertex second=vertex(other,*g); pair<Edge, bool> result=boost::edge(first,second,*g); if(!result.second){ boost::add_edge(first,second,*g); } } tokens[0] is the id of the node, tokens[1] contains the number of edges this node is pointing to. From tokens[3] until the end, one gets the nodes to which the current node is connected (stored in other) As you can see I call the function boost::edge() to check whether there is already a link between first and second. As soon as I do this I get an error in Xcode. Does anyone know what I'm doing wrong here. It probably something very simple but I don't see it. Thanks in advance Tom

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Boost.python iterator , range
by CT 18 Sep '06

18 Sep '06

Hi , Can someone can give me some help on how to expose correctly an array of object pointers using boost.python ? here is a small example of what i need i have a class class A { public: A(std::string &oName); ~A(){} const std::string &GetName() const; } class B { std::vector<*A> *poNames public: std::vector<*A> GetNames() { return *poNames } } assume that there is two instances of A in the container of the object B now for the boost::python code. I would like to be able to expose class a and class b and the vector of A* typedef std::vector<A*> array_proj; array_proj::iterator begin_array_proj(array_proj &x) {return x.begin();} array_proj::iterator end_array_proj(array_proj &x) {return x.end();} BOOST_PYTHON_MODULE(pysession) { class_<A>("object a",init<std::string &) .def("GetName",&A::GetName,return_value_policy <copy_const_reference>() ) ; class_<B>("object B") .def("GetNames", &B::GetNames, return_value_policy<manage_new_object>() ) ; class_<std::vector<*A> >("array of pointer to objects A") .def("__iter__", range( begin_array_proj, end_array_proj) ) ; } Now in python for example I call #create a new object B #and iterate over all of the object A #assume that there are two object of type A in the vector oNewSession = pysession.B() oVector = oNewSession.GetNames() for oA in oVector.__iter__(): print (oA.GetName()) i have this error when i start the python script for oA in oVector.__iter__(): TypeError: No to_python (by-value) converter found for C++ type: class ::A * Does someone can give me some help on how to expose correctly an array of pointers using boost.python ?

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Dereferencing value for algorithm
by Alexander Shyrokov 18 Sep '06

18 Sep '06

An iterator is pointing to a pointer, how do I add another dereferencing operator in the algorithm, so it works on values? void f(int& i); vector<int*> a; // this would work if f would be void f(int* i) for_each(a.begin(),a.end(),boost::bind(f,_1)); I could define a dereferencing predicate: template<class T> struct deref{ typedef T result_type; T operator()(T* p){assert(p);return *p;} }; for_each(a.begin(),a.end(),boost::bind(f,boost::bind(deref<int>,_1))); but this requires supplying a template parameter. Is there an easier way? Thanks. -- Regards, Alexander. http://sjcomp.com

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[multi_index].[example].[composite_keys]. Fails to compile with Solaris 10
by Prashant Thakre 18 Sep '06

18 Sep '06

Hi, OS: SunOS 5.10 >>CC -V CC: Sun C++ 5.8 Patch 121017-04 2006/08/02 I am trying to compile composite_keys.cpp with Sun Studio 11. After applying all the patches listed at http://developers.sun.com/prodtech/cc/downloads/ patches/ss11_patches.html, http://blogs.sun.com/roller/resources/sga/ boost_1_33_1.patch and following instructions listed at http://blogs.sun.com/ sga/entry/boost_1_33_1, am still unable to do so. However, I can compile other examples provided with multi_index. >>CC -library=stlport4 -features=tmplife -featurestmplrefstatic -fast -I$BOOST_INCLUDE composite_keys.cpp ----------------------------------------------------------------------------- boost/include/boost-1_33_1/boost/multi_index/ordered_index.hpp", line 784: Error: boost::multi_index::composite_key_compare<std::less<const file_entry*>, std::less<std::string>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>::operator()<boost::multi_index:: composite_key<file_entry, boost::multi_index::member<file_entry, const file_entry*, 21>, boost::multi_index::member<file_entry, std::string, 1>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type,boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, boost::multi_index::composite_key<file_entry, boost::multi_index:: member<file_entry, const file_entry*, 21>, boost::multi_index::member<file_entry, std::string, 1>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>(const boost::multi_index::composite_ key_result<boost::multi_index::composite_key<file_entry, boost::multi_index::member<file_entry, const file_entry*, 21>, boost::multi_index::member<file_entry, std::string,1>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>&, const boost::multi_index::composite_key_result< boost::multi_index::composite_key<file_entry, boost::multi_index::member<file_entry, const file_entry*, 21>, boost::multi_index::member<file_entry, std::string, 1>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>&) const is not accessible from boost::multi_index::detail::ordered_index<name_key, std::less<boost::multi_index::composite_key_result< boost::multi_index::composite_key<file_entry, boost::multi_index::member<file_entry, const file_entry*, 21>, boost::multi_index::member<file_entry, std::string, 1>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::nulles::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>, boost::multi_index::detail::nth_layer<1,file_entry, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<name_key, mpl_::na, mpl_::na>, boost::multi_index::ordered_non_unique< size_key, mpl_::na, mpl_::na>, mpl_::na,mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<file_entry>> , boost::mpl::vector0<mpl_::na>, boost::multi_index::detail::ordered_unique_tag>::invariant_() const. ----------------------------------------------------------------------------- similar error is reported for line 785 ("boost/include/boost-1_33_1/boost/ multi_index/ordered_index.hpp" ) regards, Prashant Thakre

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