September 2005 - Boost-users - lists.preview.boost.org

Re: [Boost-users] [Graph] Help on custom VertexList
by Nicola Vitacolonna 19 Sep '05

19 Sep '05

>> Why isn't there any "dequeS" tag in BGL? > > Historical accident. If you'd like we could add your implementation > for deque. Below you find my implementation for deque. Regards Nicola PS: sorry for forgetting the subject in my previous post, causing a mess with message threading... #include <boost/graph/graph_traits.hpp> #include <boost/graph/adjacency_list.hpp> #include <deque> namespace boost { namespace graph_detail { struct deque_tag : virtual public random_access_container_tag, virtual public back_insertion_sequence_tag { }; // No front_insertion_sequence_tag? template <class T, class Alloc> deque_tag container_category(const std::deque<T, Alloc>&){ return deque_tag(); } template <class T, class Alloc> unstable_tag iterator_stability(const std::deque<T, Alloc>&) { return unstable_tag(); } #if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION template <class T, class Alloc> struct container_traits< std::deque<T, Alloc> > { typedef deque_tag category; typedef unstable_tag iterator_stability; }; #endif } // namespace graph_detail struct dequeS { }; template <typename ValueType> struct container_gen<dequeS, ValueType> { typedef typename std::deque<ValueType> type; }; } // namespace boost // Test int main(int, char*[]) { typedef boost::adjacency_list<boost::vecS, boost::dequeS, boost::bidirectionalS> Graph; Graph g; Graph::vertex_descriptor v1, v2; v1 = boost::add_vertex(g); v2 = boost::add_vertex(g); boost::add_edge(v1, v2, g); }

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Re: [Boost-users] [boost] Beyond the C++ Standard Library: An Introduction to B oost
by Bjorn.Karlsson＠readsoft.com 19 Sep '05

19 Sep '05

Hello Beman, > From: Beman Dawes [mailto:bdawes@acm.org] > > What kind of animal is that on the cover? Some kind of Lemur? Yes, they are lemurs. In case some of you are wondering what lemurs and Boost have in common, I must confess that I have absolutely no idea. My editor, Peter Gordon, came up with the unbelievably far-fetched connection that "Boost is giving a lift to the C++ Standard Library". I think that he, just as you and I did, simply thought that they were just about the cutest things you ever saw. (When deciding which cover picture to go with, I also consulted my six-year-old son, who made it quite clear that the other options were, ahem, less perfect than the one with the lemurs.) > It is about the cutest thing I've seen in a long time. (Don't > tell my office cat I said that.) My lips are sealed. Björn

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[bind] Pointer to functions as template parameters
by Bruno Martínez 19 Sep '05

19 Sep '05

Hi. When using pointers to functions with bind, the particular function doesn't play a part in the return value's type of bind. That is void func1(); void func2(); typeid(boost::bind(&func1)) == typeid(boost::bind(&func1)) // this is true I need the types to be different to store bind objects with the serialization library. The C++ Templates book proposes an adaptor that takes the pointer to function as a template parameter. However, this adaptor is particular to a given signature, and I don't know how to rewrite it more generally. Is this possible? Can I more easily make boost::bind do what I want? Bruno

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Parsing RFC 822 date/time
by Tobias Grimm 19 Sep '05

19 Sep '05

Hi! I'm trying to parse a rfc822 date as used in RSS feeds. It looks like this: Sat, 07 Sep 2002 00:00:01 GMT Is this possible with time_facet somehow? I think at least the time zone can't be parsed, because the corresponding format specifiers are for output only. Any idea how this kind of date format should be parsed? bye, Tobias

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(no subject)
by Nicola Vitacolonna 18 Sep '05

18 Sep '05

Thank you! Actually, boost::array is an unfortunate choice, as it does not model a Sequence. But I have successfully built a vertex list out of std::deque. Which has suggested me a couple of more questions: 1) I should also overload iterator_stability() for my container, shouldn't I? 2) I did a quick test: adding vertices to a graph (adjacency_list) whose vertex list is implemented as a deque turns out to be faster than adding vertices to a vector-based (or even a list-based) graph. Why isn't there any "dequeS" tag in BGL? Regards Nicola > > Hi everybody, > > I want to use my custom container as a vertex list in a graph. I > have > > followed the documentation, but I don't know exactly how I should > > overload the push() and erase() functions. > > Sorry, looks like the documentation is incomplete in that regard. > I'll fix that. > > You can find examples of push() and erase() in: > > boost/pending/container_traits.hpp > > > The following example code, using boost::array, gives an error: "no > > matching function for call to 'container_category > (boost::array<void*, > > 10ul>&)". Can someone help me? > > You'll need to define a container_category function for boost::array. > There are examples of this also in container_traits.hpp. > > Cheers, > Jeremy

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Question about network flow examples
by Sumanth J.V 18 Sep '05

18 Sep '05

Greetings, On the edmunds-karp-eg.cpp and the push-relabel-eg.cpp, the output is is as shown below. But I dont understand how in the first flow describing line "f 0 6 3" is listed since there is not vertex with id 0. The vertices are labeled from 1 to N as I understand. Even the input file max_flow.dat in the examples folder labels the vertices from 1..N. thanx // Sample output: // c The total flow: // s 13 // // c flow values: // f 0 6 3 // f 0 1 0 // f 0 2 10 // f 1 5 1 // f 1 0 0 // f 1 3 0 // f 2 4 4 // f 2 3 6 // f 2 0 0 // f 3 7 5 // f 3 2 0 // f 3 1 1 // f 4 5 4 // f 4 6 0 // f 5 4 0 // f 5 7 5 // f 6 7 3 // f 6 4 0 // f 7 6 0 // f 7 5 0

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multi-index container: a more general basic usage example 1
by Alexander Schuh 18 Sep '05

18 Sep '05

Hi, in Example 1 there is a structure: struct employee { int id; std::string name; int age; … }; Is it possible to create automatically A) container with id as an index B) a view with name as index C) a view with age as index ? For this example it is easy to create the containers and views by hand but I plan to use at least 10 structures with many dimensions. For some containers I also need hash_indices - so there is really a lot of similar code, which I don’t want to have. Also I want to provide iterators or one general (template) iterator for all dimensions. How would you write such a general iterator? There should be a function that takes for example “employee_name” or “employee_id” as a parameter to query the employee container. It would also be interesting to have a function that creates an iterator based only on the Information, for example, multi_index::container(1)_index(2). Is there a function that calculates the max. index number of a certain container? Thank you very much, Alex Schuh -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.1/104 - Release Date: 16.09.2005

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[Graph] Help on custom VertexList
by Nicola Vitacolonna 18 Sep '05

18 Sep '05

Hi everybody, I want to use my custom container as a vertex list in a graph. I have followed the documentation, but I don't know exactly how I should overload the push() and erase() functions. The following example code, using boost::array, gives an error: "no matching function for call to 'container_category(boost::array<void*, 10ul>&)". Can someone help me? One more question: is it possible to get a reference to the vertex container, given an adjacency_list<...> object? Nicola #include <boost/graph/adjacency_list.hpp> #include <boost/array.hpp> struct arrayS { }; namespace boost { template <class ValueType> struct container_gen<arrayS, ValueType> { typedef array<ValueType, 10> type; }; } int main(int,char*[]) { typedef boost::adjacency_list<boost::vecS, arrayS, boost::bidirectionalS> Graph; Graph g(10); boost::add_vertex(g); boost::add_vertex(g); boost::add_edge(vertex(0, g), vertex(1, g), g); return 0; }

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[MPL] vector_c which contains string literals
by Hossein Haeri 18 Sep '05

18 Sep '05

Dear MPL maniacs, AFAIK, there is no mpl::vetor_c which can hold string literals. Or is it? If not, isn't there any way to implement one? Any voluteers please? Thanks in Advance, --Hossein ___________________________________________________________ Yahoo! Messenger - NEW crystal clear PC to PC calling worldwide with voicemail http://uk.messenger.yahoo.com

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Question about proper container/algorithm to use for fast dictionary lookup
by Elisha Berns 18 Sep '05

18 Sep '05

Hi, This question is whether Boost already has, or perhaps needs to have a container type that is specifically designed for fast word lookup in a UNICODE dictionary. It has occurred to me that an associative container that is specifically designed for word lookup may be much faster than the standard containers such as map, hash_map, associative_vector as they are general purpose containers. So the more detailed questions are: 1) What type of algorithm/container should be used here? 2) Would its performance be much better than a general purpose associative container? Thanks, Elisha Berns e.berns(a)computer.org tel. (310) 556 - 8332 fax (310) 556 - 2839

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