June 2007 - Boost-users - lists.preview.boost.org

[bind] using bind for << to ostream
by Mojmir Svoboda 29 Jun '07

29 Jun '07

Hello, i want to use bind to create a pair and forward it to an std::ostream, i.e. like: std::for_each(vec.begin(), vec.end(), bind(&write, std::cout, bind(constructor<std::pair<value_t, value_t> >(), _1, _1))); but the compiler says: ios_base.h:781: error: 'ios_base(const ios_base &)' is private boost/boost/lambda/detail/bind_functions.hpp:472: error: within this context boost/boost/lambda/detail/function_adaptors.hpp: In static member function `static void boost::lambda::function_adaptor< void (*)(ostream &, const pair<value_t, value_t> &) >::apply( void (*)(ostream &, const pair<value_t, value_t> &), const ostream &, const pair<value_t, value_t> &)' ... it seem that temporary is created? why? how to avoid it? i've tried the obvious way (at least for me): std::for_each(vec.begin(), vec.end(), (std::cout << bind(constructor<std::pair<value_t, value_t> >(), _1, _1))); but now the output from compiler is kind of 'heavy stuff' and i'm having difficulties to figure out what am i doing wrong. can you help me, please? many thanks for your attention, Mojmir --------8<---- complete source ------ #include <boost/lambda/bind.hpp> #include <boost/lambda/construct.hpp> #include <memory> #include <vector> #include <iostream> using namespace boost::lambda; typedef int value_t; typedef std::vector<value_t> vect_t; typedef std::vector<std::pair<value_t, value_t> > vect2_t; std::ostream & operator<< (std::ostream & os, std::pair<value_t, value_t> const & p) { return os; } void write (std::ostream & os, std::pair<value_t, value_t> const & p) { } int main () { vect_t vec; vect2_t vec2; vec.push_back(1); std::transform(vec.begin(), vec.end(), std::back_inserter(vec2), bind(constructor<std::pair<value_t, value_t> >(), _1, _1)); // ok /* std::for_each(vec.begin(), vec.end(), bind(&write, std::cout, bind(constructor<std::pair<value_t, value_t> >(), _1, _1)) ); std::for_each(vec.begin(), vec.end(), (std::cout << bind(constructor<std::pair<value_t, value_t> >(), _1, _1))); */ } This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Thank you.

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[multi-index] how to use in herit member as index
by hongleij＠126.com 29 Jun '07

29 Jun '07

//boost #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> using namespace ::boost; using namespace ::boost::multi_index; #include <string> struct Peer { std::string userid; }; struct CPeer:public Peer { int index; }; struct userid{}; typedef multi_index_container< CPeer, indexed_by< hashed_unique<tag<userid>,member<CPeer,std::string,&CPeer::userid> > > > CPeersType; //how could i use userid as an index in CPeer ,not in Peer, 一起来，150 万人同时在玩的梦幻西游

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Re: [Boost-users] [multi-index] member ar guments [Was: how to use inheritmember as index]
by hongleij＠126.com 29 Jun '07

29 Jun '07

it my implemention, i use BOOST_TYPEOF instead of typeof(). it seems work well for gcc and vc7.1 , #include <boost/multi_index/member.hpp> //for member #include <boost/multi_index/mem_fun.hpp> //for const_mem_fun using boost::multi_index::member; using boost::multi_index::const_mem_fun; #include <boost/typeof/typeof.hpp> /* MEMBER */ template<typename T> struct get_details; template<typename Class, typename Member> struct get_details<Member Class::*> { typedef Class class_type; typedef Member member_type; }; #define MEMBER(MemPtr) \ member< \ get_details<BOOST_TYPEOF(MemPtr)>::class_type, \ get_details<BOOST_TYPEOF(MemPtr)>::member_type, \ MemPtr> /* CONST_MEM_FUN */ template<typename T> struct get_fun_details; template<typename Class, typename Type> struct get_fun_details<Type (Class::*)()const> { typedef Class class_type; typedef Type member_type; }; #define CONST_MEM_FUN(MemFunPtr) \ const_mem_fun< \ get_fun_details<BOOST_TYPEOF(MemFunPtr)>::class_type, \ get_fun_details<BOOST_TYPEOF(MemFunPtr)>::member_type, \ MemFunPtr>

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Cross-compiling boost for win32 on linux
by rodolfo＠rodsoft.org 29 Jun '07

29 Jun '07

Hi, I used to be able to cross-compile boost on linux for win32 with boost.build v1 without problems, but now with v2 I cannot find the mingw toolset. It seems that now we can use gcc toolset but with a mingw flavor. So, where can I set this flavor? Everything I do makes bjam use plain g++ (for building to run on linux), not mingw32-g++ (run on win32). Regards, Rodolfo Lima.

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Why can't I catch this exception in boost::thread?
by af001 29 Jun '07

29 Jun '07

#include <boost/thread/thread.hpp> #include <iostream> #include <exception> void helloworld() { std::cout << "Hello World!" << std::endl; throw(std::string("err")); } int main() { try { boost::thread thrd(&helloworld); thrd.join(); } catch(...) { std::cout<<"err"; } } -- View this message in context: http://www.nabble.com/Why-can%27t-I-catch-this-exception-in-boost%3A%3Athre… Sent from the Boost - Users mailing list archive at Nabble.com.

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about shared_ptr
by Daniel Oberhoff 28 Jun '07

28 Jun '07

Hi all, I am using shared_ptr to ease implementation of a matlab file wrapper. Esepcially the fact that it is in tr1 and thus available on many platforms already pushed that decision. Now I was wondering about one thing: Is there a devent way, using shared_ptr, to hand out multiple references? What I mean is something like this: class Variable { shared_ptr<Variable> ref(); }; The problem with shared_ptr is, that, or so it seems, you can only create one directly from the object like this: shared_ptr<Variable> p(new Variable(...)); and all further references have to be created as copies of this (or copies of copies...). So I have to keep one of those around to make new ones. But I cannot keep one inside the class itself or else it will never be deleted (because it would reference itself). The same goes for weak_ptr, since there must be a live shared_ptr around for the object not to be deleted. The only way I can think of is implementing my own refcount and hooking into my own release method. THe problem with this is that I cannot, acoording to the docs, hook up the retain method, so each shared_ptr "cloud" (i.e. set of shared_ptrs that have been created from a common shared_ptr) is hooked up to one ref_count, so they might invalidate when the object stays alive, making any attached weak_ptrs useless. The other is using intrusive_ptr, but that a) is not in tr1 and b) does not have a weak ptr. I was also wondering why intrusive_ptr is not wrapped inside shared_ptr, i.e. why I cannot hook up both retain (increase refcount) and release into shared_ptr, but I suppose that is for the developers list. One other way I could think of would be that I keep a reference to the global ref_count of all the shared_ptrs, and creating new shared_ptrs on top of that, thus binding all shared_ptrs together, but that part does not seem to be exposed in the api. Any Ideas? Daniel Oberhoff ps: should it be possible to post to this list via gmane? I would like that much better, so this won't clog my inbox. But trying to post I keep getting error 441 in gnus

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Re: [Boost-users] [serialization] problem with derived classes
by Johan Franzén 28 Jun '07

28 Jun '07

> Hello, > > I'm having an issue with serializing derived classes from a base class > pointer. I think I've narrowed it down to the simplest possible code. I > get an "unregistered class" exception at runtime even though I've > registered the derived class with BOOST_CLASS_EXPORT. Here's the code: > [ snip ] > ----------------------------------------------- > > X.hpp: > > #pragma once > > #include <boost/serialization/base_object.hpp> > #include "A.hpp" > > class X : public A > { > friend class boost::serialization::access; > template<class Archive> > void serialize(Archive & ar, const unsigned int) > { > ar & boost::serialization::base_object<A>(*this); > } > }; > > ------------------------------------------------ > > X.cpp: > > #include "X.hpp" > > #include <boost/serialization/export.hpp> > > BOOST_CLASS_EXPORT(X) > > ----------------------------------------------- > > As you can see, I don't have BOOST_CLASS_EXPORT in the X.hpp header. > This is the way I originally had it but then I got multiple definition > link errors when more than one class derived from A. The suggestion in > the serialization docs was to move the macro to a .cpp file. [ snip ] Hello Avery, I suspect You need to BOOST_CLASS_EXPORT(A) as well, since You do try to serialize an A in X's serialize() method. This is was I ended up doing when serializing a hierarchy of derived classes and a base class. I'm not sure how to do that in Your case, since I had all classes and all BOOST_CLASS_EXPORT macros in a single header file. HTH, Johan Franzén

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Re: [Boost-users] [multi-index /mpl] fata l compile error when using a tag in VS7.1 with SP1
by hongleij＠126.com 28 Jun '07

28 Jun '07

when i clean the solution and then rebuild it,it is useless; >* Try disabling the option /Gm (Enable Minimal Rebuild.) Yes,i just turn off it,then the error disappear. ps: its really a painful thing waiting for compiling, it about 10s for that litte file in a pentium 2.8G cpu. 一起来，150 万人同时在玩的梦幻西游

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Creating a property map inside Dijkstra Visitor
by Jonas Gabriel 28 Jun '07

28 Jun '07

Good afternoon, Inside a dijkstra visitor I would like to change the edge weights at some point, so in my visitor I'm trying to make a property map called weight : > template<class DynamicMap> > class gds_visitor : public dijkstra_visitor<> > { > public: > > gds_visitor(DynamicMap input):dynamic(input){} > > .... > > template <class Edge, class Graph> > void examine_edge (Edge e, Graph& g) { > typename property_map<Graph, edge_weight_t>::type weight; > weight=get(edge_weight, g); > > std::cout << "An edge is being examined..." << "\n"; > } > > protected: > DynamicMap dynamic; > }; where Graph: > typedef adjacency_list<listS, vecS, directedS, no_property, property<edge_weight_t, int> > Graph; and Edge: > typedef std::pair<int, int> Edge; But it is not compiling, mentioning a problem with weight 'soperator = . Thank you in advance, Jonas Gabriel

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grapg problem: getting all vertices between source and sink
by gast128 28 Jun '07

28 Jun '07

Dear all, we have a simple problem: we want to know all vertices between a source and sink vertex in adirected graph. So my thoughts were to see if a vertex is reachable from both source and sink (by doing a breadth_first_search on the graph from source and a breadth_first_search from the sink on the reverse graph) and if reachable they lay in between. However this counts too much vertices. Consider graph So -> Si -> C. C is reachable from both So as reachable from Si using in edges. This is not good. The breadth_first_search should not perform an out_edge discover from Si. Do I have to implement my own breadth_first_search_with_stop or are there alternatives? Wkr, me

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