September 2002 - Boost-users

Newbie needs help w/VC6 & filesystem (take 2)
by John B. Williston 17 Sep '02

17 Sep '02

Greetings, I'm sorry for my earlier post. I didn't realize that the dir_it beta stuff was not what was being referred to as the "filesystem". I now know better, and I'm trying to make the filesystem stuff work instead. Unfortunately, I'm having no better luck. Consider the following code: #include "boost/filesystem/operations.hpp" // includes boost/filesystem/path.hpp #include "boost/filesystem/fstream.hpp" // ditto #include <iostream> // for cout int main(int iArgc, char** pArgv) { namespace fs = boost::filesystem; int iNumNodes = 0; fs::directory_iterator end_itr; // default construction yields past-the-end for (fs::directory_iterator itr("debug"); itr != end_itr; ++itr) { if (fs::is_directory(*itr)) std::cout << (*itr).file_path() << " (dir)" << std::endl; else std::cout << (*itr).file_path() << std::endl; iNumNodes++; } std::cout << iNumNodes << " total." << std::endl; return 0; } That's a relatively brain-dead use, I should think, to enumerate the contents of the debug folder to the console. Unfortunately, when I try compiling this, the linker complains horribly about all kinds of symbols already being defined in the filesystem object modules. To ditch the linker errors, I've temporarily used the /force switch, but that's hardly illuminating. First, can anyone tell me how to avoid getting a plethora of multiply-defined symbol errors? Or is /force my only real option? Second, if I use the /force switch, I get all kinds of unhandled exception errors when the directory iterator is constructing. Changing the string I pass to it at construction just changes which exception it emits. With the code above as written, the culprit is: template<typename Y> void reset(Y * p) // Y must be complete { BOOST_ASSERT(p == 0 || p != px); // catch self-reset errors this_type(p).swap(*this); } That's lines 181-185 of boost/shared_ptr.hpp, and I haven't a clue why it's freaking out. Tracing through all the code shows that the exception is occurring AFTER the swap seems to succeed. I'm stumped as to what the problem might be. But I sure would appreciate any advice y'all can offer. So far I have to say that I'm impressed with the Boost library features, but it seems a cast-iron bitch to make it actually compile and link in any real-world programs. John

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Advantage to STLport w VC7?
by dick.bridges＠tais.com 17 Sep '02

17 Sep '02

I'm preparing an upgrade from VC6 SP5 to VC7. I'm told the VC7 STL was improved but specifics are hard to come by. Can anyone tell me if there's still an advantage, <emphasis> with respect to the Boost libraries</emphasis>, to using STLport with VC7? TIA for any suggestions.

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regex 1.28.0 build (question - and problem report)
by acarsac 17 Sep '02

17 Sep '02

Hi, 2 things while upgrading from 1.25 to 1.28 : -I was trying to build the regex library (1.28.0) with msvc-stlport configuration. vc6.bat set STLPORT_PATH="c:\Mes Documents\STLport-4.5.3" nmake -fvc6-stlport.mak will fail. i had to erase some lines in vc6-stlport.mak because i guess it does not support space in path. i do the install by hand too. unless that, it work fine for me. -I was just wondering why the boost build system (jam) makes the regex library if i need to rebuild them with nmake whereas i specify the good target os for both ? Alex.

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question about edge_property_type
by wei guo 16 Sep '02

16 Sep '02

Hi, group: I have a problem of using edge_property_type. in the example file: undirected.cpp, I added several lines like: template < typename DirectedGraph > void directed_graph_demo() { const int V = 2; DirectedGraph digraph(V); typename graph_traits < DirectedGraph >::vertex_descriptor u, v; typedef typename DirectedGraph::edge_property_type Weight; typename property_map < DirectedGraph, edge_weight_t >::type weight = get(edge_weight, digraph); typename graph_traits < DirectedGraph >::edge_descriptor e1, e2; bool found; ......... Weight w1 = get(weight, e1); // <<----------- added line Weight w2 = get(weight, e2); // put( weight, e1, w1*w2/(w1+w2) ); // <<----------- added line std::cout << "weight[(u,v)] = " << get(weight, e1) << std::endl; std::cout << "weight[(v,u)] = " << get(weight, e2) << std::endl; } I got following compiling errors with KAI compiler: "undirected.cpp", line 83: error: no operator "*" matches these operands operand types are: Weight * Weight put( weight, e1, w1*w2/(w1+w2) ); ^ detected during instantiation of "void directed_graph_demo<DirectedGraph>() [with DirectedGraph=DirectedGraph]" "undirected.cpp", line 83: error: no operator "+" matches these operands operand types are: Weight + Weight put( weight, e1, w1*w2/(w1+w2) ); ^ detected during instantiation of "void directed_graph_demo<DirectedGraph>() [with DirectedGraph=DirectedGraph]" 2 errors detected in the compilation of "undirected.cpp". however, if I change the put statement in the example code to be: put( weight, e1, get(weight, e1)*get(weight, e2)/(get(weight, e1)+get(weight, e2)) ); it compiled successfully. So, what do I missing here, and what is the return type of get(weight, e2) ? and how it connected with DirectedGraph::edge_property_type ? thanks in advance! weiqing --------------------------------- Do you Yahoo!? Yahoo! News - Today's headlines [Non-text portions of this message have been removed]

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[BGL] setting a breakpoint in an algorithm visitor
by Chris Russell 16 Sep '02

16 Sep '02

p.156 of the BGL book: "... visitors are passed by value..." I was attempting to set a breakpoint in a visitor event handler (that I know is executing) but the breakpoint is seemingly ignored by my debugger. This is because the visitor I construct and subsequently pass to the algorithm is not the object that is actually dispatched by the algorithm. Correct? Using the Intel compiler under MS DevStudio 6 on Windows, I inserted a ::DebugBreak() (asm int 3) into the visitor and *do* hit that but only have assembly language and not source to step through at that point. Why are visitors passed to algorithms by value? Any suggestions for debugging visitor code at the C++ source level and not in assembly? - Regards Chris

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[BGL] Property map question
by Chris Russell 16 Sep '02

16 Sep '02

What determines when boost::get(Graph, vertex_myproperty_t) returns a boost::property_map<graph_t, vertex_myproperty>::type vs. a ::const_type? Suppose: enum vertex_myproperty_t { vertex_myproperty = 12345}; BOOST_INSTALL_PROPERTY(vertex,myproperty); typedef property<vertex_myproperty_t, MyPropertyObject, ....> vertex_properties_t; typedef adjacency_list<vecS,vecS,bidirectionalS, vertex_properties_t> graph_t; typedef property_map<graph_t, vertex_myproperty_t>::type vertex_myproperty_map_t; graph_t Graph;

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Re: Thanks for the help...
by Peter Dimov 16 Sep '02

16 Sep '02

From: "someuserat" <marktutt(a)excite.com> > > If I can impose, I've got another question that I think is in the same > area... > > I couldn't think of a way to call Widget::operator()(const WidgetPtr > w) through the smart pointer, so I wrote an equivalent method called > equals to try to imlement the following function. > > void WidgetMgr::dropWidget(const WidgetPtr w){ > > col.erase(remove_if(col.begin(),col.end(),boost::b > ind2nd(boost::mem_fn(&Widget::equals),c))); > } ... where Widget::equals takes a WidgetPtr? Based on this information, I think that you need boost::bind(&Widget::equals, _1, w) (Please use the boost-users list.) > Is there any reference to the boost libraries that goes into more > detail? I've got several books on STL that never seem to address the > issues I'm running into with smart pointers, I'm afraid what I may run > into once I really get into the meat of this project.

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RE: [Boost-Users] lexical_cast question
by Björn Karlsson 16 Sep '02

16 Sep '02

> From: Mark Snelling [mailto:mark@bakedbeans.com] > > Ok, I guess I'll just make my own temporary one based on the > original in > the meantime :) > > Mark. > Or, you could use the version with proposed changes - it's in the Files section at YahooGroups. Bjorn

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RE: [Boost-Users] lexical_cast question
by Björn Karlsson 16 Sep '02

16 Sep '02

> From: Mark Snelling [mailto:mark@bakedbeans.com] > > Hi, > Does the boost::lexical_cast library support wide character sets for > example: > > #include <boost/lexical_cast.hpp> > > using namespace boost; > using namespace std; > > void main () > { > wstring wtext(L"1234"); > int val = lexical_cast<int>(wtext); > } > Not the current version of lexical_cast - the implementation uses stringstream to perform the conversion. A proposed change to lexical_cast does handle wide characters correctly. I'm not sure about the status of that proposal, though. Bjorn Karlsson

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lexical_cast question
by Mark Snelling 16 Sep '02

16 Sep '02

Hi, Does the boost::lexical_cast library support wide character sets for example: #include <boost/lexical_cast.hpp> using namespace boost; using namespace std; void main () { wstring wtext(L"1234"); int val = lexical_cast<int>(wtext); }

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