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Problem with dijkstra_shortest_paths
by Stephen Woodbridge 01 Jul '11

01 Jul '11

Hi all, I am C programmer floundering in a C++ world! I have the function that I call from C that builds a graph, runs dijkstra_shortest_paths(), then extracts the results and passes them back to a C array of structs. Code is in pastebin: http://pastebin.com/xi7vLpTx This seems to work and everything looks ok, EXCEPT the edge ids are not correct. I suspect this is because I'm not doing something correctly and I have been messing with this for a couple weeks without success, so I think its time to ask for help. So in the function: graph_add_edge(G &graph, int id, int source, int target, float8 cost) id is the edge id source is the node id at the start of the edge target is the node_id at the end of the edge cost is the cost to traverse the edge from source to target I would really appreciate it if someone could look at this and point out what I might be doing wrong. Thanks in advance, -Steve

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Meta State Machine PseudoExit transitions
by Johan Gielens 01 Jul '11

01 Jul '11

Hello, I'm trying to implement a PseudoExitState in my boost meta state machine. This is the situation: http://i55.tinypic.com/2a83yar.png. Currently, when going from Transport to either Situation A or B, it throws an "no_transition" in the SubState for the "convertible event" needed by the PseudoExit state. (This is event6 in the example described below) According to the documentation (http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/ch03s02.html#d0e930) and the corresponding example, there should be some kind of transition triggered by "event6" from SubState2 to Substate1 (see http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/examples/DirectEntry…, in the transition table for SubFsm2). I don't see an arrow in the state diagram between SubState2 and SubState1, nor can I figure out why I would want such a transition. In my SubState's transition table, I have defined the transition from Transport to PseudoExit1 and 2: g_row< Transport , Sensor , Exit1 , &SubFront::SDownstreamCheck >, g_row< Transport , Sensor , Exit2 , &SubFront::SDownstreamNoCheck > and in the TopState from PseudoExit1 and 2 to SituationA and B: _row< Sub::exit_pt< SubFront::Exit1 > , TransportDone , SituationA >, _row< Sub::exit_pt< SubFront::Exit2 > , TransportDone , SituationB >, So do i have to handle an "TransportDone" event in the SubState? And what are my Start and End states? I would appreciate your help :) Best Regards, Johan

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Re: [Boost-users] Boost-users Digest, Vol 2769, Issue 5
by Tom Tan 01 Jul '11

01 Jul '11

------------------------------ > > Date: Thu, 30 Jun 2011 15:00:13 -0400 (EDT) > From: Jeremiah Willcock <jewillco(a)osl.iu.edu> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [Graph]questions regarding > boost::graph::adjacency_list constructor prototype > > On Thu, 30 Jun 2011, Tan, Tom (Shanghai) wrote: > > > > > While studying boost.graph, I stumbled upon this constructor definition: > > > > ????template <class EdgeIterator> > > > > ??? adjacency_list(EdgeIterator first, EdgeIterator last, > > > > ????????????????????????? vertices_size_type n, > > > > ????????????????????????? edges_size_type = 0, > > > > ????????????????????????? const GraphProperty& p = GraphProperty()) > > > > ????? : Base(n, first, last), m_property(new graph_property_type(p)) > > > > { } > > > > I have 2 questions here: > > > > -????????? What does ?edges_size_type = 0,? means here?? Assigning a value to a TYPE, instead of a parameter? Can > > anyone please point me to an explanation of this grammar usage? > > It's like if the code was "edges_size_type x = 0", but since the parameter > is not used, removing the name avoids compiler warnings. Nice to know this trick. Never knew that the 'x' can be omitted in this case. > > > > > -????????? Why the necessary of edges_size_type = 0 parameter,? since there?s a range pair of ?EdgeIterator first, > > EdgeIterator last?? > > It is not necessary, since the value of that parameter is never used. It > is probably there match the interface of some other constructor, either in > adjacency_list or some other graph class. I guessed so but it's better to confirmed. Thanks for the help. -Tom

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[Range] Select forward or reverse traversal at compile time?
by Alastair Rankine 01 Jul '11

01 Jul '11

Given a bidirectional range R, is it possible to select at compile time whether we want to iterate forwards or backwards? Below is a test app. At the commented line, I would like to transparently construct a forward or reverse range, ie either [begin(range), end(range)] or [rbegin(range), rend(range)] respectively, depending on the definition of the Reversed template parameter. Just to be clear, the desired output is: forward: abc reversed: abc I can make this work by using a functor class with partial specialisation to construct the iterator_range, using begin/end or rbegin/rend respectively. But it's a bit ugly and it would seem like something that boost range would provide anyway? (Note that boost::reverse() is NOT what I am after.) #include <boost/assign/list_of.hpp> #include <boost/range/algorithm/copy.hpp> #include <boost/range.hpp> #include <vector> #include <iostream> template <typename Reversed, typename Range> std::string Print(const Range& range) { typedef boost::iterator_range< typename boost::mpl::eval_if< Reversed, boost::range_reverse_iterator<const Range>, boost::range_iterator<const Range> >::type> IterRange; // want to convert it to a forward range here IterRange forwardRange(range); std::string result; boost::copy(forwardRange, std::back_inserter(result)); return result; } int main(int argc, char* argv[]) { using boost::assign::list_of; std::vector<char> a = list_of('a')('b')('c'); std::vector<char> b = list_of('c')('b')('a'); std::cout << "forward: " << Print<boost::mpl::false_>(a) << std::endl << "reversed: " << Print<boost::mpl::true_>(b) << std::endl; return 0; }

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[Graph]questions regarding boost::graph::adjacency_list constructor prototype
by Tan, Tom (Shanghai) 30 Jun '11

30 Jun '11

While studying boost.graph, I stumbled upon this constructor definition: template <class EdgeIterator> adjacency_list(EdgeIterator first, EdgeIterator last, vertices_size_type n, edges_size_type = 0, const GraphProperty& p = GraphProperty()) : Base(n, first, last), m_property(new graph_property_type(p)) { } I have 2 questions here: - What does "edges_size_type = 0," means here? Assigning a value to a TYPE, instead of a parameter? Can anyone please point me to an explanation of this grammar usage? - Why the necessary of edges_size_type = 0 parameter, since there's a range pair of "EdgeIterator first, EdgeIterator last"? Does anyone have an answer? Thanks.

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ptime input_facet error with %f flag at converting string to ptime (1.36, 1.44)
by Sören Freudiger 30 Jun '11

30 Jun '11

Hello I have problems with reading the time fraction at converting from string to ptime. Here is the regarding soruce code: |#include <iostream> #include <string> #include <boost/date_time.hpp> #include <boost/date_time/posix_time/posix_time.hpp> #include <boost/date_time/gregorian/gregorian.hpp> #include <boost/date_time/posix_time/conversion.hpp> int main( int, char * ) { using namespace std; using namespace boost; using namespace boost::posix_time; using namespace boost::local_time; using namespace boost::gregorian; time_facet* output_facet= new time_facet(); time_input_facet* input_facet= new time_input_facet(); stringstream sstream; sstream.imbue(locale(locale::classic(), output_facet)); sstream.imbue(locale(sstream.getloc() , input_facet)); string format("%d/%m/%Y %H:%M:%S.%f"); //example works fine without %f!!! output_facet->format( format.c_str() ); input_facet->format( format.c_str() < /span>); ptime dt= microsec_clock().local_time(); sstream.str(""); sstream<< dt; cout<< sstream.str() << end l; string time_string= sstream.str(); ptime tgtDt( boost::date_time::not_a_date_time); sstream.str( time_string.c_str() ); sstream>> tgtDt; cout<< tgtDt<< endl; }| The program runs fine without the %f inside the format string. But with %f tgtDt is "not-a-date-time". I use boost 1.44 and the doc says %f shold work, because every input incompatible format flag is marked bei "!" in the documentation. Any ideas how to get the frac part out of a string?

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Boost Atomic ?
by John M. Dlugosz 30 Jun '11

30 Jun '11

I was surprised to see that the Boost distribution doesn't have the "atomic" operations library. I expected it to be part of the Threading, modeled on the C++0x draft. I found <http://www.chaoticmind.net/~hcb/projects/boost.atomic/> via Google, from 2009. But N3225=10-0215 (is there a later Draft available ?) §29.2 shows lots of change bars, and the <atomic> header seems completely redone, it appears to make everything nicely templatated. I wonder if this is at all up-to-date, or why it's not already more officially part of Boost. Does anybody know? More to the point, I want to write some code that is portable across platforms, including emerging platforms like tablets which I expect will be more varied in their CPU architecture. I've been spoiled with writing x86-only for so many years! It makes sense to use the constructs that will be shipped with the compiler some day. So, where can I find that? —John

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Question about fusion::map
by Frank Astier 29 Jun '11

29 Jun '11

Hi - I'm using fusion::map, and I've noticed that if I have: struct attr0 {}; typedef fusion::pair<attr0, double> Attr0; struct attr1 {}; typedef fusion::pair<attr1, double> Attr1; And then: typedef fusion::map<Attr0> ProfileType1; typedef fusion::map<Attr0, Attr1> ProfileType2; When I create N instances of ProfileType2, the process size at runtime is about twice the size of the same process creating N instances of ProfileType1. No big surprise, I guess, but if I *never* mention the type Attr1 in my code, is there a way to "remove" it at compile time from ProfileType2? I.e. I would want the compilation to remove the parts of the fusion::map that are guaranteed not to be used at runtime, so that I don't spend memory that I will never use. Is that possible? Thanks a lot! Frank fastier(a)yahoo.com

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Re: [Boost-users] Using Boost::Bind
by David McCallum 29 Jun '11

29 Jun '11

I should clarify, this is what I want to achieve: boost::function<void (DBuffer&)> singleHandler; void addHandler(boost::function<void (DBuffer&)> newHandler) { singleHandler = newHandler; } The problem is that I don't know how to call boost::bind with a DBuffer parameter, where DBuffer is one of my own classes. > You will want to learn a bit more about Boost.Bind. You can bind your > pointer or variable at the bind call. Parameters at the time of bind are > copied by value. If you need a reference use the boost::ref wrapper. > Expanding your example: > void DClient::resolveHandler( const boost::system::error_code& error, > int value ); > ... > int special_number = 42; > > hostResolver->async_resolve( *nameQuery, > boost::bind(&DClient::resolveHandler, this, > boost::asio::placeholders::error, > special_number ) ); > > ------------------- > > In the above, when the handler is invoked it will pass the error value > (via the placeholder) and the value of special_number during the bind... > which is 42. If I understand you correctly, then in the following code: void DClient::resolveHandler(int param) { .... } boost::function<void (int)> functionPtr; int tempInt = 12; myHandler = boost::bind(&DClient::resolveHandler, this, tempInt); myHandler(67); The final line will call resolveHandler with a parameter of 12, rather than 67? Surely that can't be right?

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Re: [Boost-users] [msm] EUML submachine without macro
by ray＠maya-studio.com 29 Jun '11

29 Jun '11

Christophe Henry wrote: > you're just a little too fast as I added the example in the 1.47 release. In > the meantime, the submachine example can be found there: > http://svn.boost.org/svn/boost/trunk/libs/msm/doc/HTML/examples/CompositeTu… Thank you for quick reply! Works like a charm. Kudos for your excellent library! Best Regards, Ray

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