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[BGL] Daisy chaining algorithms using vistor mechanism?
by Chris Russell 02 Oct '02

02 Oct '02

Still up hacking... Without cluttering the question with a ton of detail, basically I need to perform a DFS on a forest stored in a bidirectionalS adjacency_list and then perform a subgraph traversal in response to each finish_vertex invocation in the visitor. (The idea is to push information down the branches towards the root of a tree in the forest). Calling in_edges(v,g) from within the finish_vertex method in a dfs_visitor will not compile however. This is because the graph is passed by const reference into the visitor method and in_edges requires a non-const graph reference? (this seems similar in spirit to a question I posted a week or two ago about boost::get(some_property, Graph) from within a visitor). Generally, I would like to be able to daisy chain graph algorithms - that is invoke a sub-algorithm from within a visitor method called by a controlling algorithm. This would require that the sub-algorithm not change the graph topology, trample on properties used by its controller (e.g. coloring), or otherwise invalidate vertex descriptors or iterators so some care would need to be taken in designing the sub-algorithm. But it seems like a useful mechanism for extension. Am I missing something about getting at the in_edges given that I'm working with a const graph_t& in the context of the "controlling" DFS' visitor method? Why is this so restrictive? I'm guessing it might have something to do with having multiple copies of vertex and edge iterators floating around but I'm not sure. Will you comment on this please Jeremy? Thank you. - Chris Russell

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RE: [Boost-Users] MPL?
by Mark Storer 02 Oct '02

02 Oct '02

"Modern C++ Design" has a pretty good coverage so far (I'm on chapter 6 out of 11). As for impressing the ladies... well... you could always show them your stamp collection. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard; -----Original Message----- From: Jeff Faust [mailto:jeff@opticalres.com] Sent: Wednesday, October 02, 2002 12:37 PM To: Boost-Users(a)yahoogroups.com Subject: RE: [Boost-Users] MPL? Well, I didn't know I needed boost until I saw it. Same for STL several years back. 'Metaprogramming' comes up a lot on the boost list, but I have no understanding about what it's for--what problems it solves. The documentation is sparse. Then this thread comes up and everybody talks about it like it's obvious. I dislike being baffled. But mostly it's curiosity. I need something to talk about at parties and impress the ladies. MPL will do that, right? Right? Hello? Jeff -----Original Message----- From: David B. Held [mailto:dheld@codelogicconsulting.com] Sent: Wednesday, October 02, 2002 12:14 PM To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] MPL? ----- Original Message ----- From: "Jeff Faust" <jeff(a)opticalres.com> To: <Boost-Users(a)yahoogroups.com> Sent: Wednesday, October 02, 2002 11:32 AM Subject: [Boost-Users] MPL? > [...] > Can anybody explain in English what the following does? I believe that Aleksey posted the runtime pseudo-equivalent. > Posted by David Abrahams on boost developers list: > > Have I mentioned recently how totally cool MPL's lambda facility is? > > I can't believe I can do things like this, even with MSVC6. It makes my > > metaprograms SO much easier to manage! > > mpl::logical_and< > > is_reference_to_class<add_reference<mpl::_> > > > , mpl::logical_not< > > is_reference_to_args<add_reference<mpl::_> > [Aleksey, on 9/27] // "ideal" version, for comparison purposes: // is_reference_to_class( add_reference(_) ) // && !is_reference_to_args( add_reference(_) ) I can't say for sure what the code does myself, but if I could venture a guess, I would say that it's a condition for something else (maybe an iterative algorithm over a type container?) that checks to see if an argument is a reference type of various sorts. Basically, if you don't understand it, in this case, you probably don't need it. ;) I know I don't! Dave Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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RE: [Boost-Users] MPL?
by Randy Bowen 02 Oct '02

02 Oct '02

Metaprogramming techniques are discussed pretty thoroughly in Andrei Alexandescru's "Modern C++ Design" and in Czarnecki and Eisenecker's "Generative Programming". --Randy -----Original Message----- From: Jeff Faust [mailto:jeff@opticalres.com] Sent: Wednesday, October 02, 2002 12:37 PM To: Boost-Users(a)yahoogroups.com Subject: RE: [Boost-Users] MPL? Well, I didn't know I needed boost until I saw it. Same for STL several years back. 'Metaprogramming' comes up a lot on the boost list, but I have no understanding about what it's for--what problems it solves. The documentation is sparse. Then this thread comes up and everybody talks about it like it's obvious. I dislike being baffled. But mostly it's curiosity. I need something to talk about at parties and impress the ladies. MPL will do that, right? Right? Hello? Jeff -----Original Message----- From: David B. Held [mailto:dheld@codelogicconsulting.com] Sent: Wednesday, October 02, 2002 12:14 PM To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] MPL? ----- Original Message ----- From: "Jeff Faust" <jeff(a)opticalres.com> To: <Boost-Users(a)yahoogroups.com> Sent: Wednesday, October 02, 2002 11:32 AM Subject: [Boost-Users] MPL? > [...] > Can anybody explain in English what the following does? I believe that Aleksey posted the runtime pseudo-equivalent. > Posted by David Abrahams on boost developers list: > > Have I mentioned recently how totally cool MPL's lambda facility is? > > I can't believe I can do things like this, even with MSVC6. It makes my > > metaprograms SO much easier to manage! > > mpl::logical_and< > > is_reference_to_class<add_reference<mpl::_> > > > , mpl::logical_not< > > is_reference_to_args<add_reference<mpl::_> > [Aleksey, on 9/27] // "ideal" version, for comparison purposes: // is_reference_to_class( add_reference(_) ) // && !is_reference_to_args( add_reference(_) ) I can't say for sure what the code does myself, but if I could venture a guess, I would say that it's a condition for something else (maybe an iterative algorithm over a type container?) that checks to see if an argument is a reference type of various sorts. Basically, if you don't understand it, in this case, you probably don't need it. ;) I know I don't! Dave Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=233351.2428261.3848243.2225242/D=egroupweb/S=17050067…> <http://us.adserver.yahoo.com/l?M=233351.2428261.3848243.2225242/D=egroupmai…> Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . [Non-text portions of this message have been removed]

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Iterator adapters and maps
by Alisdair Meredith 02 Oct '02

02 Oct '02

I have a std::map<std::string, MyObject> and want to iterate over it calling several member functions of MyObject. This seems like a good case to learn about transform/projection iterator, but I am having a hard time getting a compiling example. My most recent attempt looks like this: class MyObject { public: void CommitChanges(); void RollbackChanges(); // More implementation details would follow }; typedef std::map<std::string, MyObject> MyMap; typedef MyMap::iterator MyIterator; typedef MyMap::value_type mapped_type; typedef boost::projection_iterator_generator< Select2ndRef<mapped_type>, MyIterator >::type projection; MyMap theMap; projection begin( theMap.begin() ); projection end( theMap.begin() ); for_each( begin, end, mem_fun_ref( MyObject::CommitChanges ) ); I also have the following two templates, although I suspect their equivalent must be lurking in boost somewhere: template<class pair_type> struct Select1stRef { typedef typename pair_type::first_type & result_type; result_type operator()( pair_type &source ) const { return source.first; } }; template<class pair_type> struct Select2ndRef { typedef typename pair_type::second_type & result_type; result_type operator()( pair_type &source ) const { return source.second; } }; I am compiling using BCB5 compiler in the IDE, should be equivalent to the free 5.5.1 command line compiler. While I could simply write a forwarding functor in a fraction of the time it will take me to solve this, there is definitely a ne tool I would like to add to my toolbox here once I understand what is happenning. Unfortunately I am getting somewhat lost in reference-to-reference issues, and the occasional compiler crash does not help. Any and all hints appreciated -- AlisdairM

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Loki vs. Boost
by Hamlet 02 Oct '02

02 Oct '02

Hi, I'm (desperately) looking for a serious comparative review of Loki vs. Boost libraries. Although the differences are quite clear, still it would be nice to see a serious comparison, especially in the features that exists in both places, i.e. smart pointers, small obj. allocator, type traits and template meta-programming. Does anybody knows if there exists such a paper somewhere, or alternatively have his own insights about the libraries? Thanks, Ariel

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[BGL] vertex_index_t w/VertexList=listS questions
by Chris Russell 02 Oct '02

02 Oct '02

Hi Jeremy, Using adjacency_list w/VertexList=listS, I've stuffed a vertex_index_t declaration into the internal vertex property map and got my DFS invocation to compile. Taking a look at the dijkstra-example-listS.cpp in the examples directory on CVS, I see how you manually initialize this property for each of the vertices after you build up the graph. p.230 of the book discusses the auto-update of the vertex_index_t property upon vertex removal for the case of VertexList=vecS but I'll need to affect this update myself for VertexList=listS? Also, can you foresee any problems if I register vertex_index_t with a value_type of long int instead of int? I'm guessing no because I'm passing it as a template parameter but I just want to make sure. - Thanks and regards Chris Russell

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BOOST_PARAM_TEST_CASE and uncaught exceptions
by Alisdair Meredith 02 Oct '02

02 Oct '02

I have a case where my test case passed to BOOST_PARAM_TEST_CASE is throwing an exception I was not expecting. This seems to still result in the correct number of calls to the test case, but the first parameter in the list is passed every time. Is this a feature of my compiler, or an issue with the library? Using Borland C++ Builder 5 (should be same as free command-line compiler) -- AlisdairM

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BUG: intrusive pointer and weak_ptr
by Petr Ferschmann 01 Oct '02

01 Oct '02

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, I think I found BUG. Let we have this program: - -- cut here -- #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <boost/intrusive_ptr.hpp> #include <cstdio> using namespace std; #define INTR class MujObjekt #ifdef INTR : public boost::counted_base #endif { public: MujObjekt() { printf( "MujObjekt::MujObjekt()\n" ); } void setThis( boost::shared_ptr<MujObjekt> obj ) { m_this = obj; } virtual ~MujObjekt() { printf( "MujObjekt::~MujObjekt()\n" ); } boost::weak_ptr<MujObjekt> m_this; }; int main() { boost::shared_ptr<MujObjekt> obj( new MujObjekt() ); obj->setThis( obj ); return( 0 ); } - --- cut here --- But in case of usage of intrusive pointer it doesn't call destructor - because there is weak pointer. But when I undefine INTR and it uses non-intrusive it works as expected. This is only modelling case to simulate bug. - -- Petr "Fers" Ferschmann -=[ petr(a)ferschmann.cz ]==[ http://petr.ferschmann.cz/ ]=- - -=[ Koukni na http://www.postcard.cz/ ]==[ +420 604/781 009 ]=- GPG Fingerprint: [83B0 6378 7A9D D993 035E 60BD FEEC F665 D2C8 1B9A] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (GNU/Linux) iD8DBQE9mV9O/uz2ZdLIG5oRArF/AJ9LGfWTXfy69zNTsbiEKThTPQnWcwCeOWgj 0tX9AxdWJ8u/L1MkdZHjOPk= =7A3i -----END PGP SIGNATURE-----

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RE: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'?
by dick.bridges＠tais.com 30 Sep '02

30 Sep '02

1) There are circumstances where the 'creator' should stick around as long as one or more 'creations' still exist (e.g., a [network] session that's created various asynchronous conversations). 2) I haven't had time to check, but I think this is the as-yet-not-but-soon-to-be-released implementation of intrusive pointers. Interesting: search google for "intrusive pointer" (quotes not required). I got five hits - all of the URLs start with www.boost.org/. BTW: Really slick. Trying to figure out where to keep "THE POINTER" was driving me nuts. I'd completely forgotten about intrusive pointers. Thanks. A *LOT*. Mark Storer <mstorer@cardiff To: "'Boost-Users(a)yahoogroups.com'" <Boost-Users(a)yahoogroups.com> .com> cc: Subject: RE: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'? 09/30/2002 09:36 AM Please respond to Boost-Users I've got a comment and a question... 1) Couldn't the "backpointer" just be a constant reference? Backpointers, in my mind, don't have anything to do with ownership, so a shared_ptr woulnd't be appropriate. 2) shared_from_this? I can't find that one in any of the headers or docs I downloaded with 1.28. I did find shared_count in (oddly enough) shared_count.hpp, which looks like it would prevent two seperate shared_ptr's from causing a double-delete... pretty slick, but I couldn't find any docs on it. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard; -----Original Message----- From: David Abrahams [mailto:yg-boost-users@m.gmane.org] Sent: Sunday, September 29, 2002 4:12 PM To: boost-users(a)yahoogroups.com Subject: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'? <dick.bridges(a)tais.com> wrote in message news:OF699D7956.EED22A4F-ON88256C43.00722AD0@tais.net... > I run into situations where it's useful for an object to have a > 'backpointer' to the object instance that created it (example below). Is > there a pattern/idiom for doing this using shared_ptr? Or maybe I need to > re-think the idea of the backpointer in the first place? > class Bar; class Foo { public: Foo(shared_ptr<Bar>); private: shared_ptr<Bar> p; }; class Bar : boost::shared_count { void doit() { new Foo(boost::shared_from_this(this)); // <<< new Foo(this) obviously won't work. } }; HTH, Dave -- ----------------------------------------------------------- David Abrahams * Boost Consulting dave(a)boost-consulting.com * http://www.boost-consulting.com Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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RE: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'?
by Mark Storer 30 Sep '02

30 Sep '02

I've got a comment and a question... 1) Couldn't the "backpointer" just be a constant reference? Backpointers, in my mind, don't have anything to do with ownership, so a shared_ptr woulnd't be appropriate. 2) shared_from_this? I can't find that one in any of the headers or docs I downloaded with 1.28. I did find shared_count in (oddly enough) shared_count.hpp, which looks like it would prevent two seperate shared_ptr's from causing a double-delete... pretty slick, but I couldn't find any docs on it. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard; -----Original Message----- From: David Abrahams [mailto:yg-boost-users@m.gmane.org] Sent: Sunday, September 29, 2002 4:12 PM To: boost-users(a)yahoogroups.com Subject: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'? <dick.bridges(a)tais.com> wrote in message news:OF699D7956.EED22A4F-ON88256C43.00722AD0@tais.net... > I run into situations where it's useful for an object to have a > 'backpointer' to the object instance that created it (example below). Is > there a pattern/idiom for doing this using shared_ptr? Or maybe I need to > re-think the idea of the backpointer in the first place? > class Bar; class Foo { public: Foo(shared_ptr<Bar>); private: shared_ptr<Bar> p; }; class Bar : boost::shared_count { void doit() { new Foo(boost::shared_from_this(this)); // <<< new Foo(this) obviously won't work. } }; HTH, Dave -- ----------------------------------------------------------- David Abrahams * Boost Consulting dave(a)boost-consulting.com * http://www.boost-consulting.com Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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