July 2003 - Boost-users - lists.preview.boost.org

boost::shared_ptr and stl algorithms
by Bill Eidson 15 Apr '05

15 Apr '05

std::vector< boost::shared_ptr<T> > TVec; I want to write a function object to run std::for_each. to do somework against members of T and accumulate results in functor. My attempts have failed in VC7 with memory errors in my operator() method. struct fo { bool operator()( boost::shared_ptr<T>& t ) { return true; } }; Thanks in advance bille

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BGL and reversing / moving edges
by joshrose 17 Dec '03

17 Dec '03

G'day, I was hoping someone might be able to tell me if they've run into any situations using BGL where they needed to move (or reverse (i.e. flip the source and target)) an edge within a graph implemented as an adjacency_list. I'm working on an implementation of an algorithm for max. weight bipartite matching ("the assignment problem"), and one of the assumptions in the algorithm is that non-matched edges are directed from one subgraph, A, to the other subgraph, B, and matched edges are directed the other way. Over the course of growing the matching, a simple way to add and remove edges from the candidate set is just to reverse the edge, thus the need for some way to reverse the edge within BGL. I don't think I can just remove and then re-add the edge in the other direction, primarily because doing so will (I believe) invalidate any edge_descriptors referring to that edge. In particular, there are property maps keeping track of the weight of edges, the predecessors of certain nodes, etc. that use edge descriptors as keys. I've spent a fair bit of time reading the documentation and looking through the implementation of adjacency_lists (incl. edge_list_impl), and I'm not really sure of a way to either move an edge directly within a graph, or even to create a new edge from another s.t. they have the same edge_descriptor (in general a bad thing, probably). Anyone have any thoughts on this? Thanks, -Josh

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tuples: operator ==
by Konstantin M. Litvinenko 12 Aug '03

12 Aug '03

Hello, All! I can't compile this simple test: --------------------------------------------- #include <boost/tuple/tuple.hpp> #include <iostream> using namespace boost::tuples; using namespace std; int main() { typedef tuple<int, tuple<int, int> > Tuple; Tuple t1(1, make_tuple(1, 1)); Tuple t2(2, make_tuple(2, 2)); if (get<1>(t1) == get<1>(t2)) { cout << "equal"; } else { cout << " not equal"; } return 0; } ----------------------------------------- What am I doing wrong? Compilers: Borland Builder 6 (bcc32.exe 5.6.4) and VC7 With best regards, Konstantin M. Litvinenko aka Dark Angel.

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Linking with BGL adjacency_list_io.hpp
by Solomon Gibbs 05 Aug '03

05 Aug '03

Hi, I'm having trouble linking code that uses adjacency_list_io.hpp. If the header is included is included in more than one compilation unit, I get "multiple definition of function" errors for the non-template functions in adjacency_list_io.hpp: std::istream& operator >> ( std::istream& in, no_property& ) and void getSubset( no_property& p, const no_property& s ) I'm sure that there is some C+ subtlety that I'm missing here, but I'm not familiar enough with the library to understand what it is. Shouldn't non-template function code be in a .cpp file to keep this sort of thing from happening? - Solomon

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A Quick Question about Threads
by Paul Grenyer 01 Aug '03

01 Aug '03

Hi All I'm planning on replacing all our (Win32 API Wrapped) threads with the boost threads. I was looking at the thread class interface and there isn't a method to ask if the thread is still running. This is something we use quite a lot in out current wrapper. To get around this I was thinking of using a member variable in the function object that is passed to the thread constructor to indicated whether the thread had finished. Is there a better way? I've not had a really good look at the docs yet, but there doesn't appear to be a Critical Section class. Should I be using the Mutex for synchronisation instead? -- Regards Paul Paul Grenyer Email: pjgrenyer(a)iee.org Web: www.paulgrenyer.co.uk EvaneScence: http://www.evanescence.com

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Graph Library: Ordered Vertex List?
by dmatt001 01 Aug '03

01 Aug '03

Hi Guys, I would like to use an ordered vertex list (ie based on property type) in an implementation that I am working on such that duplication can be avoided. I have read and understand how to implement an ordered edge list thanks to the previous posts but am finding it hard to get started! Perhaps I have missed the key example? It appears that from the way config::VertList is constructed that it may be a similar process in nature? adj_list_impl::add_vertex appears to discard the boolean return value from the associative insertion. Would such a construction allow me to avoid the duplication I seek to avoid? I am guessing so, but some advice would give me a confidence "boost". ( <-- It's a lame pun: I really do need help ;-) ) My first steps are below rehashing the excellent ordered edges example with a simple search/replace and maching my target container base. I'll keep plugging along with it anyway and it may just compile one day. Suggestions/Ideas/Refs/Ptrs are appreciated. Matt --- first guess follows --- template <class VertDesc> struct order_by_name : public std::binary_function<VertDesc,VertDesc,bool> { bool operator()(const VertDesc& v1, const VertDesc& v2) const { // Order by vertex name. return boost::get(boost::vertex_name, v1) < boost::get(boost::vertex_name, v2); } }; #if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION struct ordered_set_by_nameS { }; namespace boost { template <class ValueType> struct container_gen<ordered_set_by_nameS, ValueType> { typedef std::set<ValueType, order_by_name<ValueType> > type; }; } #else struct ordered_set_by_nameS { template <class T> struct bind_ { typedef std::multiset<T, order_by_name<T> > type; }; }; namespace boost { template <> struct container_selector<ordered_set_by_nameS> { typedef ordered_set_by_nameS type; }; } #endif

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Compile time Problem with boost::type_traits library
by Amit Bhatia 01 Aug '03

01 Aug '03

Hello, I am trying to use the boost::function library which in turn includes many of the headers from other boost libraries. I am using g++ 3.2 with: g++ -c -g -fwritable-strings -Wno-deprecated -static -ansi -pedantic -DANSI_HEADERS -D_G_HAVE_BOOL as the options. The file is_integral.hpp and the file is_convertible.hpp in the type_traits library contain the declarations of the type long long which the ISO C++ seemingly doesn't accept. The compiler gives the warning: ISO C++ does not support `long long' . I don't think there is a new version of this on boost. I downloaded the boost lib sometime in June Version 1.30.0. Can this problem be because of any of the compiler options that I am using? thanking you, regards, amit.

3 2

Spirit Sequential-or
by Bruno Martínez 01 Aug '03

01 Aug '03

Hi boosters, In operators.html (a || b) is said to be equivalent to (a | b | a >> b), but, if I understand precedence correctly, it should be equivalent to (a >> b | a | b). I'm just learning Spirit, so this may probably be my mistake, right? Cheers, Bruno Martinez ---------------------------------------------------- ATENCION Su servicio de correo tiene antivirus ?? @internet URUGUAY: http://www.internet.com.uy

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FC++ in Boost, Spirit, Preprocessing
by Jan Kybic 31 Jul '03

31 Jul '03

Hello, I want to write in favor of Boostifying the functional library FC++, which I find very useful. Would a merger with the Phoenix library from Spirit (already in Boost) be feasible? Phoenix seems to have a slightly nicer syntax but lacks (as far as I know) the Haskell prelude functions and lazy list implementation, also the closures do not seem very intuitive to me. My main concern with both FC++ and Phoenix is that when defining new functiods, the user needs to write a lot of often repetitive code. This could be simplified using a suitable preprocessor. Would that be acceptable and are there other people interested ? Yours, Jan -- ------------------------------------------------------------------------- Jan Kybic <kybic(a)ieee.org> tel. +420 2 2435 7264 or <kybic(a)fel.cvut.cz>, http://cmp.felk.cvut.cz/~kybic

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date_parsing.hpp.patch
by Tonal 31 Jul '03

31 Jul '03

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