- Boost-users - lists.boost.org

RE: [Boost-Users] Re: Is there a "known issues" page anywhere?
by Jim.Hyslop 03 May '03

03 May '03

Alisdair Meredith [mailto:yg-boost-users@gmane.org] wrote: > "Jim.Hyslop" wrote: > > > There is a "Known Issues" section on the wiki (see the link in the > > auto-appended .sig) which is intended to document these > common "gotchas". I > > haven't looked at it for a while, so I don't know how > up-to-date it is. > > I tried looking there first, and after your message went back for a > second look. > Perhaps I am being dense, but I really can't find it. > Closest match is > the 'build issues' page, which I think is for a different thing. > 'Search' the wiki did not help either. That's the page I meant - CommonBuildProblems: http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?CommonBuildPr oblems Sorry about the confusion. Your problem with the lexical_cast is the precise reason I created the page. > Could you post a link to the precise page you were thinking > about? And > I think a more prominent link on the front page may be useful too. There's one under the "Quick Links" section, but as you say it's not very prominent. Remember, the point of a wiki is that *anyone* can change the information. If you think it deserves a more prominent position, then you are free to give it one :=) -- Jim

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PP library...
by Eric Robert 02 May '03

02 May '03

Hi, I think the preprocessor library could help me here but I'm having problems understanding it. Maybe someone will be so kind to explain it to me a bit. Here is what I want to produce: void foo(char); void foo(int); void foo(unsigned int); .... You got the idea. Something that repeats a list of things i.e. here, types. How can I do that? Thanks! Eric [Non-text portions of this message have been removed]

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Code Fail
by Hossein Haeri 02 May '03

02 May '03

Dear all, There is a tiny cpp file attached to this message that raises the following exception while running: "Project ConstStatProject.exe raised exception class EAccessViolation with message 'Access violation at adress ...'. Process stopped. Use Step or Run to continue." and stops at the following line of the share_ptr library: if(use_count_ == 0 && weak_count_ != 0) boost::throw_exception(boost::bad_weak_ptr()); Can anybody help me? BTW, I'm using BCB6. Thanks, --Hossein __________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com [Non-text portions of this message have been removed]

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[BGL] Online Graph Algorithms (fwd)
by David Pearce 02 May '03

02 May '03

Hello, I am interested in how boosters think online graph algorithms should be written. I have looked at the connected_components algorithm and feel that it breaks some of the ideas behind generic programming. For example, consider the following: > typedef adjacency_list <vecS, vecS, undirectedS> Graph; > Graph G(6); > add_edge(0, 1, G); > add_edge(1, 4, G); > > // create the disjoint-sets structure, which requires > // rank and parent vertex properties > ... > initialize_incremental_components(G, ds); > incremental_components(G, ds); > > generic_algorithm_which_adds_edges(G); At this point, the connected_components data structures may be out-of-sync. Now, I suppose that we could write a wrapper class which looked like a "Graph" and provides its own add_edge to update "ds" correctly. However, this seems overly cumbersome. It strikes me that a better way of doing this would be to use an abstract base class, like so: > template<class T, ...> > class connected_components : public T { > ... > }; > > template<class T> > pair<T::edge_descriptor, bool> > add_edge(connected_components<T>::vertex_descriptor t, ...) { > // do stuff > return add_edge(static_cast<T::vertex_descriptor>(t), ...); > } Thus, we supply "Graph" as the base class and can then safely pass it to "generic_algorithm_which...". So, does anyone know of any reasons not to do this? Cheers, David J. Pearce

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const shared_ptr<>
by Hossein Haeri 02 May '03

02 May '03

Dear all, I'm a newbie in boost! I want to know what the following means: int a = 5; const boost::shared_ptr<int> sp(&a); Does it mean that the following line is an error? *sp = 7; If so, what are the guarantees? Is there any documented guarantee? (I couldn't find anything in the documentation. Excuseme if I'm careless!) Thanks, --Hossein __________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com

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RE: [Boost-Users] Is there a "known issues" page anywhere?
by Jim.Hyslop 02 May '03

02 May '03

Alisdair Meredith [mailto:yg-boost-users@gmane.org] wrote: > Is there a place where known problems for libraries/compilers are > stored? > > For instance, trying to use boost/time we hit a problem with MSVC7 and > lexical_cast unless we enable the "wchar_t as a native type" option. > While this may be good practice <g> it is not the default, > and caught us > out (and the error is none-too helpful) > > I can imagine this sort of issue is discovered and re-discovered on a > regular basis, and wonder where to look for such known issues before > using list bandwidth. There is a "Known Issues" section on the wiki (see the link in the auto-appended .sig) which is intended to document these common "gotchas". I haven't looked at it for a while, so I don't know how up-to-date it is. If that issue's not documented there, would you mind adding it? -- Jim

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graph (BGL): bad documentation
by schlumpfi106 02 May '03

02 May '03

I just tried to use the boost graph library to create a spanning tree generation algorithm. After wasting a whole day I gave up and wrote all the graph code myself. I'm quiet upset about the useless online documentation for the graph library. Maybe I have to buy the book to be able to use it? Normally I would rely on some good, instructive examples and start my own program by copy-and-paste. Here, there are only a few examples and they are either too simple or too specific. Most documentation topics provide no examples at all. Sometimes I head to guess through the template-loaded headerfiles because there was no documentation. I failed in creating a graph from a given adjacency matrix. I failed in understanding the "interior property" concept. I failed in printing a graph and its properties to graphviz. To the developers: Please, before you implement anything new -- document the old things.

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RE: [Boost-Users] Regexp Homework :-)
by Ben Hutchings 01 May '03

01 May '03

Simon Brown <simon.brown(a)kns.ch> wrote: > A few days ago I received great help with a regexp question - > now here's > another which I doubt can be done. > > Question: if the text string contains three words AAA BBB AAA > then return > the string (if any) which is repeated two or three times. > > Examples: > AAA AAA AAA return AAA > AAA BBB AAA return AAA > AAA AAA BBB return AAA > AAA BBB CCC return <nothing> > > Can this be done with a regular expression? Match against "(\\w+) (?:\\1 \\w+|\\w+ \\1)|\\w+ (\\w+) \\2" and return the match for whichever sub-expression (1 or 2) was matched. (I tested this with Python not Boost regex, but they should be compatible.)

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Is there a "known issues" page anywhere?
by Alisdair Meredith 01 May '03

01 May '03

Is there a place where known problems for libraries/compilers are stored? For instance, trying to use boost/time we hit a problem with MSVC7 and lexical_cast unless we enable the "wchar_t as a native type" option. While this may be good practice <g> it is not the default, and caught us out (and the error is none-too helpful) I can imagine this sort of issue is discovered and re-discovered on a regular basis, and wonder where to look for such known issues before using list bandwidth. -- AlisdairM

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regexp match question
by Simon Brown 01 May '03

01 May '03

Hi All, Here's a question I can't answer. I'm using regexp to dig out strings from data received via Ham Radio, so the txt often is corrupted. What I want to match is two consecutive callsigns separated by whitespace, for example 'hb9drv hb9drv' but not 'hb9drv hb9drX'. I can define the match condition for a callsign, but can I use the match option {2,3} somehow to match the same callsign two or three times? Effectively match the same word two or three times? Help received with much thanks, Simon Brown, Casa Bergenia, CH-7031 Laax www.hb9drv.ch [Non-text portions of this message have been removed]

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