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[BGL] Dijkstra shortest paths with custom compare function and zero weight edges
by Christian Ofenböck 27 May '15

27 May '15

I'm using dijkstra_shortest_paths with a custom compare function like (Weight a, Weight b) { return a<=b; } As I've also got some zero weight edges within the graph this leads to problems with the test for negative weights in dijkstra_bfs_visitor's examine_edge-function. The test fails on checking zero weight edges and throws a negative_edge-exception (dijkstra_shortest_paths.hpp:190): if (m_compare(m_combine(m_zero, get(m_weight, e)), m_zero)) evaluates to if(0<=0) Any suggestions on how to solve this issue? For now I just got rid of the test, as I just use unsigned weight values, but of course that's not a sound solution.

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question about filtered_graph
by breadbread1984 25 May '15

25 May '15

I am using boost graph library. In order to get a filtered graph, I adopted filtered_graph. I thought it could be used in the same way as adjacency_list. But when I get target and source from an edge of a filtered graph, I realized the target and source function doesn't accept filtered_graph as its argument. How can I get the two terminals of an edge from a filtered_graph then? Thanks for any hints in advance.

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[Serialization] STL Containers and Non-Default Constructors
by Trevor Thoele 24 May '15

24 May '15

I have recently changed from a hand-rolled serializer to Boost's and while it's mostly been fantastic, there's one problem that I can't seem to shake - I cannot get it to serialize non-default constructible types. It fails on trying to generate code that requires the usage of a default constructor. In non-associative types (list/deque/vector), the loader seems to be calling the container's resize function with a default value_type argument, resulting in the attempted creation of the object through the default constructor. In associative types, the loader attempts to create a default constructed value_type, which results in an std::pair being defaultly constructed with one of the pieces being the non-default constructible type. The code below fails during compilation with the error "'A' : no appropriate default constructor available". It was built with MSVC++2013. #include <list> #include <fstream> #include <boost\archive\binary_iarchive.hpp> #include <boost\archive\binary_oarchive.hpp> #include <boost\serialization\access.hpp> #include <boost\serialization\list.hpp> class A { private: template<class Archive> void serialize(Archive &archive, unsigned int version) { archive & myInt; } friend boost::serialization::access; public: int myInt; A(int myInt) : myInt(myInt) {} A(const A &arg) : myInt(arg.myInt) {} A& operator=(const A &arg) { myInt = arg.myInt; return *this; } bool operator==(const A &arg) const { return myInt == arg.myInt; } }; namespace boost { namespace serialization { template<class Archive> inline void load_construct_data(Archive &archive, A *a, unsigned int file_version) { ::new(a)A(0); } } } int main() { { std::ofstream stream("file"); boost::archive::binary_oarchive archive(stream); std::list cont; cont.push_back(A(1)); archive << cont; } { std::ifstream stream("file"); boost::archive::binary_iarchive archive(stream); std::list cont; archive >> cont; } } My question is: is this behavior known and what is the best solution to this for an end-user? The tutorial for STL container serialization mentions using load/save_construct_data to get around this problem, yet the attempted code generation above do not take that solution into account so compilation will fail even if you overload those templates. The only solutions I can think of to circumvent this problem would be to require a public (the code ultimately fails in std code, which I guess you may be able to friend but would be quite strange) default constructor, or to hand-roll STL container serialization through non-intrusive serialize/save/load overloads and skip the provided overloads entirely. -- View this message in context: http://boost.2283326.n4.nabble.com/Serialization-STL-Containers-and-Non-Def… Sent from the Boost - Users mailing list archive at Nabble.com.

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How to create a subgraph of a graph with specified vertexes?
by ffmm3＠163.com 24 May '15

24 May '15

Hi, I have a graph with several vertexes and edges, now I want to creates a subgraph object with the specified vertex set. What should I do? 发自 Windows 邮件

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Is it Okay to Use the Boost Logo
by - 22 May '15

22 May '15

I tried to find out more about the licence for the logo but didn't get very far, but I now see that on Wikipedia the logo is also released under the Boost License so I presume that I can use it for my project page.

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Please help: boost::format and Borland C++ version 0x564 errors
by Royce 22 May '15

22 May '15

I'm trying to use boost::format with Borland C++ Builder 6 (Compiler version 0x564) and can't get the boost code to compile. The code was working with sprintf but I need to be able to use numbered args (i.e. "The first string is %1% and the second string is %2%." ) for localization so that the language translators can change the position the arguments appear in the translated text. I get an "E2270 > expected" error in line of integral_c.hpp (boost 1_45_0). which is template< bool C > The code near the error is: #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) \ && !BOOST_WORKAROUND(__BORLANDC__, <= 0x551) BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_OPEN // 'bool' constant doesn't have 'next'/'prior' members template< bool C > struct integral_c<bool, C> { BOOST_STATIC_CONSTANT(bool, value = C); typedef integral_c_tag tag; . >From what I can tell I should not have to define BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION, and defining it I breaks working code. I did find a reference to a bug that affects version Borland compiler versions 0x561 to 0x580 and I tried defining BOOST_BCB_PARTIAL_SPECIALIZATION_BUG. That did not help, but at least it didn't break anything. I am able to create a small test project and it works. I was able to get the same basic code to work in 50 or 60 places in 21 of the 23 *.cpp units in my primary project. This worked in my test code but broke in my main project. std::stringstream ss; ss << boost::format(LoadStr(STestWithString).c_str()) % "First" % "Second"; AnsiString translatedMsg = AnsiString(ss.str().c_str()); ShowMessage(translatedMsg); This also worked in my test program, but broke in my main project. std::string sRawMsg; AnsiString sDebug1 = "testArg1"; AnsiString sDebug2 = "testArg2"; sRawMsg = (boost::format("Testing %1% was first. %2% was second.") % sDebug1.c_str() % sDebug2.c_str()).str(); // ignoreW8080(boost::none); // Suppress false warning - Compiles to a nop. Any suggestions on solving this problem would be greatly appreciated. Royce Fessenden White Knight Software <http://www.whiteknightsw.com/> www.WhiteKnightSw.com 417.766.1852 royce(a)fessenden.com

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Re: [Boost-users] threads and async questions and asnwers
by Victor Yankee 21 May '15

21 May '15

> > From: Michael Powell <mwpowellhtx(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] threads and async questions and asnwers > Message-ID: > < > CAMEoF_FUUVLa1Cq9_kCRLB-bSRMhH1fni5ft71-4pU-qvAy4fQ(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > On Thu, May 21, 2015 at 4:18 PM, Victor Yankee > <victor.whiskey.yankee(a)gmail.com> wrote: > > Hello List, > > > > I have a thread with a class and its method that raises a "question" > signal > > and needs to wait with a timeout for an "answer" signal. > > > > There are several worker threads, some of which may be connected to the > > question signal. The answer signal will be raised by a worker thread > only if > > it knows the answer; it is possible that no worker thread knows the > answer > > so no answer signal will be raised (hence need for timeout). The > question > > thread cannot know which worker thread to ask. > > Sounds like a homework question to me. Besides which, the problem > statement pretty much spelled out where you likely need to focus. > This is not homework; your response was not helpful. > > > What is a good way to achieve this using boost 1.58 and/or C++11? I am > using > > g++ 4.9 on 64bit ubuntu 14.04. > > > > Thanks, > > Vic

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String split behaviour
by Venkateswara Rao Sanaka 21 May '15

21 May '15

Hi, I am getting two empty strings from the following program, void boost_split_test() { const string &text("-"); vector<string> tokens; split(tokens, text, boost::is_any_of("-"), token_compress_on); cout << "size of tokens " << tokens.size() << '\n'; for (auto const &e : tokens) cout << e.size() << '\n'; } Output: size of tokens 2 0 0 Is this expected output? I expecting an zero split parts. Could someone clarify? -- Thanks, :) Venki.

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Does lock-less queue wait on empty queue ?
by Ran Shalit 21 May '15

21 May '15

Hello, I'm newbie of boost library. I would like to ask if the lockless queue waits on empty queue ? (I actually need it to wait). And another thing: Can the Pool library be build separately, so that I can use only the boost/pool files or do I need to use all boost sources in order to build just the pool. Thank you, Ran

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[boost][algorithm] Overload of boost::algorithm::all_of_equal
by dariomt＠gmail.com 21 May '15

21 May '15

Hi list, I usually find useful an overload of this function to check whether all elements in a range are equal *to each other*. Something like: template <typename Range> bool all_of_equal(const Range & r) { // return true on empty range if (boost::empty(r)) return true; // return true if all other elements are equal to the first element return boost::all_of_equal( boost::next( boost::begin(r) ), boost::end(r), *boost::begin(r)); } Would this be a useful addition to Boost.Algorithm?

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