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[graph] [beginner] How to use the "tie(...) feature" with standard c++ containers?
by Christoph 10 Oct '11

10 Oct '11

Hi recently i started programming with the boost graph library. You can use nice syntax for iterating over a set of vertices or edges by writing for example: //begin program #include <iostream> #include <boost/graph/adjacency_list.hpp> typedef boost::adjacency_list < boost::listS, boost::vecS, boost::bidirectionalS> my_graph; typedef boost::graph_traits <my_graph> my_graph_traits; int main() { my_graph g(5); my_graph_traits::vertex_iterator vi, vi_end; for (boost::tie (vi, vi_end) = vertices (g); vi != vi_end; ++vi) { std::cout << "vertex: " << *vi << std::endl; } } //End program Outputs: vertex: 0 vertex: 1 vertex: 2 vertex: 3 vertex: 4 My question is now how to define functions 'tie(...)' and 'elements(...)' for using them with standard containers. Suppose you have a container like the list: std::list <unsigned int> list(4); Now to iterate over all elements i would like to write something like //begin snippet std::list <unsigned int>::iterator begin, end; for (tie (begin, end) = elements (list); begin != end; ++begin) ;// do some thing //end snippet In stead of writing: //begin snippet begin = list.begin(); end = list.end(); for (; begin != end; ++begin) ;// do some thing //end snippet I started defining the function elements(...) like this: template <typename T> std::pair < typename T::iterator, typename T::iterator> elements (T container) { return std::make_pair(container.begin(), container.end()); } The compiler tells me, that 'tie' was not declared in this scope. So i assume that i also have to define the 'tie' function in some way. Maybe there is already some functionality to access the standard containers the way you can do it with 'tie' or maybe you could give me some hint to solve the problem. best regards Christoph

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Is boost graph library match my needs?
by ohad barta 09 Oct '11

09 Oct '11

Hi I am a Technion's reserch assistant , and right now Im looking for a graph library. The main use that I'm gonna do with graphs is routing (I am gonna use disjoint paths on a graphs, probably de bruijn graphs, in order to express some permutation). Do you think that using the BGL will be efficient in that case? Thanks in advance Ohad

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[regex] expression: string iterator not dereferencable
by Mitin Slava 09 Oct '11

09 Oct '11

Good day. I use boost::regex with ICU. When I try call u32regex_match for symbol with code 0xDA10, I get an expression "string iterator not dereferencable (xstring, line 112)". If I use other symbol (for example, "X") it works correctly. If I use wregex (wighout ICU) it works correctly too. What could be the problem? The code: #include "stdafx.h" #include <iostream> #include <conio.h> #include <boost/regex.hpp> #include <boost/regex/icu.hpp> int _tmain(int argc, _TCHAR* argv[]) { boost::u32regex delimiterRegex = boost::make_u32regex(L"\\W <file:///\\W> "); std::wstring symbol = L"X"; symbol[0] = wchar_t(0xDA10); // <= for this symbol if (boost::u32regex_match(symbol, delimiterRegex)) // <= assertion here std::cout << "success" << std::endl; else std::cout << "not match\n"; _getch(); return 0; } I checked it for boost_1_47_0. MSVC 2008 compiler. Thank you in advance, Slava Mitin

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[serialization] problem with free funciton splitting
by Jonathan 09 Oct '11

09 Oct '11

Hi, i have a code like this: //LightSetup template<class Archive> void save(Archive &a, const Mrl::LightSetup& LightSetup, unsigned int version) { unsigned int Count=LightSetup.NumLights(); a & serialization::make_nvp("Count", Count); for(unsigned int i=0; i<Count; ++i) { a & serialization::make_nvp("Light", LightSetup[i]); } } template<class Archive> void load(Archive &a, Mrl::LightSetup& LightSetup, unsigned int version) { unsigned int Count; a & serialization::make_nvp("Count", Count); LightSetup=Mrl::LightSetup();//clear everything for(unsigned int i=0; i<Count; ++i) { Light* NewLight=0; a & serialization::make_nvp("Light", NewLight): LightSetup.Add(Light); } } namespace boost { namespace serialization { template<class Archive> inline void serialize( Archive & ar, Mrl::LightSetup & t, const unsigned int file_version ){ split_free(ar, t, file_version); } }} //BOOST_SERIALIZATION_SPLIT_FREE(Mrl::LightSetup) (I tried both version, the makro and the serialize implementations, both give me the same error). The compiler says: boost\boost/serialization/split_free.hpp(45): error C2664: 'boost::serialization::save': Konvertierung des Parameters 2 von 'const Mrl::LightSetup' in 'const boost_132::detail::shared_count &' nicht möglich (converting parameter 2 not possible). I have no idea what this shared_count is, so I don't know, what do do. King regards Jonathan Klein

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[Boost Test Library] Dead links in documentation
by Boost lzw 09 Oct '11

09 Oct '11

Hello, I am reading the document from the following link: http://www.boost.org/doc/libs/1_47_0/libs/test/doc/html/tutorials/new-year-… and encountered two dead links ("Listing1", "Listing2") in the second-to-last paragraph. Are they intentionally removed? I hope I can read these listings to fullly appreciate the test library in Boost. Thanks. Robert

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a tuple from a pair?
by Krzysztof Żelechowski 07 Oct '11

07 Oct '11

How come a tuple, being a generalisation of a pair, cannot be constructed from one? I mean something along the lines make_tuple (pair const &p) { return make_tuple (p.first, p_second); } Would be good to have.

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[graph] template beginner question: How to create a template parameter option
by Christoph 07 Oct '11

07 Oct '11

Hi, i would like to create a generic function, that returns a random bipartite graph like this: enum graph_type {bipartite, none_bipartite}; template <typename Graph> Graph generate_random_graph (unsigned int num_vertices, graph_type t, double density) { if (density > 1) { std::cout << "value of parameter density in Function generate_random_graph is out of range (0.0 - 1): " << density << std::endl; exit(-1); } if (t == bipartite) { Graph g(2*num_vertices); for (int i = 0; i < num_vertices; ++i) for (int j = 0; j < num_vertices; ++j) if (std::rand()%100 <= 100*density) add_edge (i, j+num_vertices, g); return g; } else return Graph(99); // dummy part } @ Then i realized that the option parameter 'graph_type' in 'generate_random_graph' should be a template parameter, too. Like the way we use a template parameter 'boost::undirectedS' in typedef boost::adjacency_list < boost::listS, boost::vecS, boost::undirectedS> my_graph; I don't know where to start from here. I tried to find out the way the 'boost::undirectedS' thing works but i was lost in code jungle. Any assistance is welcome. Maybe you know a nice reference for me to start. If you have any other criticism, please do not hide, i am eager to learn. bye Christoph

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[BGL] boost/graph/graph_utility.hpp - cannot find any documentation
by Christoph 07 Oct '11

07 Oct '11

Hi, i would like to know why it is, that there is no documentation about boost/graph/graph_utility.hpp Functions like 'print_graph' or 'print_edges' are used quite often in the examples, for instance here http://www.boost.org/doc/libs/1_47_0/libs/graph/doc/filtered_graph.html For a newbie, as i am, it is always confusing to have to deal with undocumented functions. How should i start in such a case. I finally did something like find ./ | xargs grep print_edges inside of my boost directory. Are there any other undocumented functions within the Boost Graph Library? best Regards Christoph

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[result_of] Simple question
by Robert Jones 07 Oct '11

07 Oct '11

Morning All It's first thing in the morning for me, so maybe my neurons aren't warmed up, but I was surprised this doesn't work. #include <boost/utility/result_of.hpp> #include <boost/function.hpp> typedef boost::function<int(char)> my_function_type; typedef boost::result_of<my_function_type>::type my_return_type; Doesn't Boost.Function support 'result_of', or am I missing something obvious? If not, is there some other idiom for this, bearing mind that 'my_function_type' might be a Boost.Function, or a true function, or a Boost.Bind? Thx, - Rob.

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Boost IPC shared queue
by sidharth shanbhag 07 Oct '11

07 Oct '11

Hi, I am trying to build a shared queue between a reader and writer thread of my process. I am creating a managed shared memory segment, defining an allocator on top and using the same to initialize a shared queue. I have a question related to the edge case, considering there is a disparity in the speed of the reader and writer threads and the writer thread pumps in more data than the shared segment size, what is the expected behavior of the queue? Will it allocate a new memory segment or block the writer thread or throw an exception? Are there any links or references for the same? I had a look at the boost ipc documentation, but did not see any text explaining this scenario. Thanks and regards, Sid

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