July 2006 - Boost-users - lists.boost.org

Re: [Boost-users] shared_ptr implicit dynamic cast
by Andrew Holden 12 Jul '06

12 Jul '06

foo = boost::shared_ptr<Foo>(new Bar); foo = boost::shared_ptr<Bar>(new Bar); Scott McMurray wrote: > > The important difference is in the default deleter. shared_ptr<Foo>'s > default deleter will call delete on a Foo* while shared_ptr<Bar>'s > default deleter will call it on a Bar*. Since your base class's > destructor is virtual, it doesn't make any difference in the example. > If your destructor were non-virtual, then you'd have to use > shared_ptr<Bar>(new Bar) to get the correct destructors called. (But > without any virtual functions, the dynamic casting wouldn't compile.) Are you sure about that? A check of the documentation lists the signature for that constructor as template<class Y> explicit shared_ptr(Y * p); The explanation is given as follows: [This constructor has been changed to a template in order to remember the actual pointer type passed. The destructor will call delete with the same pointer, complete with its original type, even when T does not have a virtual destructor, or is void. The reset function has a similar signature.

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shared_ptr implicit dynamic cast
by eric 12 Jul '06

12 Jul '06

hello given the following class hierarchy class Foo { protected: virtual ~Foo() {} }; class Bar : public Foo {}; and declaration boost::shared_ptr<Foo> foo; is there any difference between the two assignment statements below? foo = boost::shared_ptr<Foo>(new Bar); foo = boost::shared_ptr<Bar>(new Bar); in other words, when you assign a value to a shared_ptr, does it make any difference what class you specify for that value, as long as the class of the underlying object can be dynamically cast to the class that was used to declare the shared_ptr? kind regards, eric

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Boost tests
by kirill.sukhonosenko 12 Jul '06

12 Jul '06

Hello, Are there any ready-to-use tests for boost which can be ran after build to prove consistency of the built libraries? I've tried to build several versions of Boost for TI DaVinci chip (ARM core) and failed. Both 1-31 & 1-33 versions failed. Some libraries has got built, some - not. How can one be assured that built libraries work properly? Thanks, Kirill

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boost [C++ database development library]
by Sundaram Ramasamy 12 Jul '06

12 Jul '06

Hi, Can someone help me to locate cross-platform (platform independant) and cross-database C++ database development BOOST library? Thanks and regards, Sundaram Ramasamy Sundaram.Ramasamy(a)saama.com

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fs::exists() question
by Simon Lacroix 11 Jul '06

11 Jul '06

Hello all, I started using the file system about a week ago in order to port a Windows application using win API calls to manipulate folders and file on Linux. So far it works great but I am having one issue, the fs::exists() function seems to throw an exception when I try to look for directory containing special characters like ./test[0] ./test<1> etc. Is this normal ? I can create directory with these characters using mkdir in Linux so it should be legal names. Any ideas ? Thanks for your time Simon

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c array parameter in resize method of multi_array
by Manuel.Yguel＠inrialpes.fr 11 Jul '06

11 Jul '06

Hi, is there any reason to refuse a resize method for multi_array that accept a C array as parameter ? As long as the resize method just works if the boost::extents parameter has the same dimension as the array to be resized a call like that: typedef boost::multi_array<double, 3> array_type; array_type A( boost::extents[3][4][2] ); ---> A.resize( {6;5;2} ); could be understood as: A.resize( boost::extents[6][5][2] ); without any ambiguity, am I wrong ?

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[graph] remove_if algorithm
by Loïc Joly 11 Jul '06

11 Jul '06

Hello, I'm new to the graph library, but I'm missing some algorithms that I believe are quite low level, and that I expected to find. For instance, I'd like to be able to remove nodes from a graph that meet some criterion. The closest I could find to remove_if was : - Iterate on each node manually: for (tie(vi, viend) = boost::vertices(myGraph) ; vi != viend; ++vi) { if (criterion(vi) { clear_vertex(*vi, myGraph); remove_vertex(*vi, myGraph); } } But I'm afraid of iterator invalidity - Filter, copy, swap: Graph tempGraph; { filtered_graph<Graph, keep_all, Criterion> fg (myGraph, criterion); copy_graph(fg, tempGraph); } copy_graph(tempGraph, myGraph); Will one of my attempts work ? Is there any other solution I missed ? Best regards, -- Loïc

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Re: [Boost-users] erase and iterators
by David Klein 11 Jul '06

11 Jul '06

boost-users-bounces(a)lists.boost.org wrote: > On 7/11/06, David Klein <d.klein(a)ascaron.com> wrote: >> you can use Boost.Lambda for this >> >> #include <boost/lambda/lambda.hpp> >> >> using namespace boost::lambda; >> >> std::vector<int> v; >> ... >> v.erase(std::remove_if(v.begin(), v.end(), 5 == _1)); >> > Shouldn't it be > v.erase( std::remove_if(v.begin(), v.end(), 5 == _1), v.end() > ); as you want to erase the range, not just the single element? > > ~ SWMc > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users <blush> of course, my bad (... actually i blame the heat in our office ;) ) </> -- dave

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Re: [Boost-users] erase and iterators
by David Klein 11 Jul '06

11 Jul '06

boost-users-bounces(a)lists.boost.org wrote: > On Tue, Jul 11, 2006 at 10:19:05AM +0000, Roman Neuhauser wrote: >> # kneeride(a)gmail.com / 2006-07-11 17:31:23 +1000: >>> On 7/11/06, Michael Nicolella <boost(a)mike-n.com> wrote: >>>> vec.erase( std::remove_if( vec.begin(), vec.end(), >>>> some_condition_functor >>>> ) ); >>> >>> Mike, I do like your remove_if example. >>> >>> i am not familar with this approach, can you please give me an >>> example of defining a some_condition_functor? for example when the >>> value == 5. > > What about this? > > Let's assume the vector contains ints > > class condition_functor { > > public: > > bool operator()(int elem) > { > return elem==5 > } > }; > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users you can use Boost.Lambda for this #include <boost/lambda/lambda.hpp> using namespace boost::lambda; std::vector<int> v; ... v.erase(std::remove_if(v.begin(), v.end(), 5 == _1)); -- HTH dave

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[serialization] skipping data
by Joel de Guzman 11 Jul '06

11 Jul '06

Hi, Here's a use case that I can't seem to find a way to do using boost.serialization. Say with version 1, I want to serialize X Y and Z. These are hierarchical and expensive data structures. Now, with version 2, I do not need to create Y objects anymore. Yet, I still have to open version 1 files for backward compatibility. So, when loading version 1 files, I want to skip reading Y objects. How do I do that without having to create a temporary Y object that will be discarded later? (I'm particularly interested with XML archives. If I had control over the xml parser, that would simply mean ignoring everything from the current tag until the next matching tag is found). Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net

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