August 2002 - Boost-users - lists.boost.org

boost::shared_ptr and stl algorithms
by Bill Eidson 14 Apr '05

14 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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bug report: boost::tokenizer with VC6
by Navi Singh 09 Feb '03

09 Feb '03

The boost release 1.28.0 of the tokenizer library has the following problem: There are 5 examples, namely, simple_example_1.cpp thru simple_example_5.cpp If I change the main() in each of the 5 to to main1() thru main5() and return 0; the vc60 compiler generates an internal compiler error when parsing the file boost\iterator_adapters.hpp on line 869, where it is parsing the following lines: reference operator*() const { return policies().dereference(*this); }

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Q: Graphs. Sorting edges. Possible? How to?
by stas_fomin 07 Nov '02

07 Nov '02

Hello. I a newbie in BGL and I rewrite my LEDA code now... I have to sort (order) edges according to some functor. For example (simplified): typedef adjacency_list<vecS, vecS, bidirectionalS> MyGraph; typedef graph_traits < MyGraph >::edge_descriptor MyGraphEdge; typedef graph_traits < MyGraph >::edge_iterator MyEdgeIter; class MyCompareEdges{ public: bool operator()(MyGraphEdge e1, MyGraphEdge e2) const { return true; } }; .... { MyGraph Gr(10); MyEdgeIter ei_beg, ei_end; MyCompareEdges comp; tie(ei_beg, ei_end) = edges(Gr); std::sort(ei_beg, ei_end, comp); //Error C2676 } And I have error C2676 (below the message...). Questions: 1. Is it possible to sort edges in the graph? 2. How to... Thanks all in advance... Stas Fomin. P.S. vecS, setS, listS for edge container... - C2676. ------------------------------ d:\projects\lib\cpp_libs\libboost\boost\iterator_adaptors.hpp(264) : error C2676: binary '+=' : 'class std::list<struct boost::list_edge<unsigned int,struct boost::no_property>,class std::allocator<struct boost::list_edge<unsigned int,struct boost:: no_property> > >::iterator' does not define this operator or a conversion to a type acceptable to the predefined operator d:\projects\lib\cpp_libs\libboost\boost\iterator_adaptors.hpp (911) : see reference to function template instantiation 'void __thiscall boost::default_iterator_policies::advance(struct boost::iterator_adaptor<class std::list<struct boost::lis t_edge<unsigned int,struct boost::no_property>,class std::allocator<struct boost::list_edge<unsigned int,struct boost::no_property> > >::iterator,struct boost::detail::undirected_edge_iter_policies,class boost::detail::edge_desc_impl<struct boost::b idirectional_tag,unsigned int>,class boost::detail::edge_desc_impl<struct boost::bidirectional_tag,unsigned int>,class boost::detail::edge_desc_impl<struct boost::bidirectional_tag,unsigned int> *,struct boost::multi_pass_input_iterator_tag,int> &,i nt)' being compiled Error executing cl.exe.

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Possible bug in boost_1_28
by Christopher Henrich 11 Oct '02

11 Oct '02

This bug comes up when I try to include <boost/array.hpp> in certain CodeWarrior projects. (CodeWarrior 8.0, running under Mac OS 10.1.5 on G3 "beige tower") If I initialize the project with stationery "C++ Console Mach-O", and I change HelloWorld.cp to include <boost/array.hpp>, then I get this error message: Error: undefined identifier 'ptrdiff_t' suffix.hpp line 204 included from config.hpp: 57 array.hpp:27 HelloWorld.cp: 10 If I initialize with PowerPlant stationery, I do not have this problem. Chris Henrich

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Problem using 'shared_ptr<T>::operator impl-defined-type()'
by Hickman, Greg 30 Sep '02

30 Sep '02

With Borland 5.5.1, I'm not having any luck using a shared_ptr in a boolean context. The compiler complains that the 'if' condition below contains an "Illegal structure operation". Is this a known deficiency with my compiler? -Greg Hickman #include <boost/shared_ptr.hpp> int main(int argc, char* argv[]) { boost::shared_ptr<int> intp; if (intp) // error here ; return 0; }

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[BGL] How to change the type of vertex_descriptor??
by Erik Arner 13 Sep '02

13 Sep '02

Hi, I have a BGL graph in the following manner: typedef adjacency_list < vecS, vecS, directedS, no_property, property <edge_weight_t, int, property <edge_weight2_t, double> > > Graph; I also have: typedef graph_traits<Graph>::vertex_descriptor Vertex; Now, the default vertex_descriptor seems to be unsigned int. How do I change this to int? Also, where (in which file) is the default set? On another note: the online reference manual is pretty good in my opinion, but it's hard to get a real overview of the contents. It also lacks an index, making it hard to look up questions like the one above. Is the book any better in this respect? Any other references worth looking up - books or webpages? Thanks, Erik

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[BGL] Problem with kevin-bacon sample
by Nicolas Guilhot 13 Sep '02

13 Sep '02

Hi all, I compiled the kevin-bacon sample on a linux box without any problem, but when I try to run the program, I obtain an error output instead of what is expected. Any help would be appreciated. Here is the output off the program : kevin-bacon: /boost_1_27_0/boost/token_iterator.hpp:75: void boost::detail::tokenizer_policy<Type, TokenizerFunc>::increment (Iterator &) [with Iterator = boost::iterator_adaptor<boost::detail::token_iterator_base<const char *>, boost::detail::tokenizer_policy<basic_string<char, string_char_traits<char>, __default_alloc_template<true, 0> >, boost::char_delimiters_separator<char, string_char_traits<char> > >, basic_string<char, string_char_traits<char>, __default_alloc_template<true, 0> >, const basic_string<char, string_char_traits<char>, __default_alloc_template<true, 0> > &, const basic_string<char, string_char_traits<char>, __default_alloc_template<true, 0> > *, forward_iterator_tag, ptrdiff_t>, Type = basic_string<char, string_char_traits<char>, __default_alloc_template<true, 0> >, TokenizerFunc = boost::char_delimiters_separator<char, string_char_traits<char> >]: Assertion `b.base().valid_' failed. Abandon Thanks for any answer. Nicolas

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BGL and Intel v6 compiler?
by Chris Russell 13 Sep '02

13 Sep '02

Lack of partial template specialization and MSVC 6.0 "Internal Compiler Error" has me looking for alternatives. Specifically, I'm considering moving some BGL-dependent code into a library and compiling it with the Intel v6.0 compiler for Windows which can produce object code and libraries that I can link into a MSVC 6.0 project. Can anyone comment on the Intel compiler's support for partial specialization - I'm not finding much except number crunching benchmark comparisons. Thanks - Chris

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n-ary ordered tree template in boost ??
by Marc Cromme 05 Sep '02

05 Sep '02

Dear Boost Members I was wondering if there is an n-ary ordered tree template in boost, something like template <size_t N, class Type, class Alloc = allocator<Type > > class NTree which is a standard container, and a reversible container, ordered by level. That is, first element is root, next series of elements are childs of roots, next series are grandchilds of root , and so on. This way one could parse level by level like a reversible container. There should be the obvious member functions for inserting/deleting child nodes and subtrees. As far as I can see, there is not such a template in boost, but the question is then: 1) can it be emulated using the grah library ?? or 2) is there already an proposal/prototype for such a thing ?? or 3) would it be interesting to include such a thing in boost ?? your's sincierely, Marc Cromme

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