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Re: [Boost-users] [RMI-like-lib] is there any interest in such?
by Foster Gareth 19 Sep '05

19 Sep '05

> Jarl Lindrud has done a lot of work on this already - see > > http://www.codeproject.com/threads/RMI_For_Cpp.asp > > While it uses boost and mpl techniques extensively it's not > quite boost style. > I'd be using it extensively but for the fact that it doesn't > integrate well with > our own code framework. > Looks interesting. Just out of interest, could you site any examples, or point me toward previous discussion that does so? Cheers, Gaz

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Find all the shortest path from a graph
by Giulio Veronesi 19 Sep '05

19 Sep '05

Hi all, I'd like to extract all possible shortest path from a source to a destination... not only one path. Please, could you help me to resolve this problem? Thanks a lot in advance, Giulio

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locate vertex
by Giulio Veronesi 19 Sep '05

19 Sep '05

Hi, I would like to locate an edge of a graph starting from the source and target vertex. For instance vertex(n, g) return the nth vertex of graph g. I would access the edge from vertex x to vertex y... something like this edge(x, y, g) Is there a fast way to do this? Thanks, Giulio

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[RMI-like-lib] is there any interest in such?
by Slawomir Lisznianski 19 Sep '05

19 Sep '05

I've been thinking of a library that would bring RMI-like capabilities to C++ (RMI stands for Remote Method Invocation). Primary goal, and differentiating feature, of this library is not to rely on IDL-like compiler, hence no cross-language support either -- if you need that, check out CORBA (www.omg.org) or ICE (http://www.zeroc.com) As an example, I'm going to "implement" client and server sides of a trivial calculator using proposed library. Step 1. Define calculator interface ----------------------------------- // // Operations: add, subtract, multiply and divide // struct add { typedef function2<double, double, double> function_type; }; struct subtract { typedef function2<double, double, double> function_type; }; struct multiply { typedef function2<double, double, double> function_type; }; struct divide { typedef function2<double, double, double> function_type; }; // Calculator interface // typedef interface< operation<sum>, operation<subtract>, operation<multiply>, operation<divide> > calculator_i; Step 2. Client invocation ------------------------- // Construct a proxy to the remote calculator // instance. Arguments to the constructor // describe remote object's location (not shown). // proxy<calculator_i> calculator(...); // Call `subtract' on remote object (call // doesn't block). Returned object implements // Asynchronous Completion Token (or Future) // concept. // act<double> res = call<subtract>(calculator, 12, 43); // Retrieve actual result, or get an exception... // double result = res(); Step 3. Server implementation ----------------------------- // Implement actual calculator. // struct calculator_servant { double sum(double a, double b) { return a + b; } ... // other operations here }; // Instantiate calculator servant // calculator_servant servant; // Create a TCP listener. // tcp_listener listener(...) // Create a stub object that acts as an // adapter between transport and a servant. // stub<calculator_i> calculator(listener); // Install operation handlers. // calculator.register_function<add>(bind(&calculator_servant::sum, ref(servant), _1, _2)); ... // register remaining handlers // Start accepting calls. // calculator.activate(); // Block until exiting. // calculator.wait_for_shutdown(); ... -- end of example] I'm fairly satisfied with the client side, but I'm not so enthusiastic about the server side though. For one, it feels less safe. For example, what if a user forgets to register a "handler" for a particular operation? Any way to enforce this at compile time? Typically, say with CORBA, IDL compiler generates operations as pure virtual functions, so at compile time, the user knows what's left out in her servant. On the other side, it's quite powerful too (being able to "bind" functors to operations, that is). Would that be a problem for you or you'd see it as a good feature? Let me know what you think. Cheers, Slawomir Lisznianski

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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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