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range_ex
by Richard Ulrich 28 Oct '09

28 Oct '09

Hi list, what's the status of range_ex? I read that it was accepted into boost half a year ago. So, will it make it into 1.41? This week I downloaded it from the boost vault, as the version from the svn sandbox seemed to be outdated. I like it very much so far. Just two remarks/questions: - in my measurements using the piped adapters (filtered / transformed) was on average 4% slower than hand coded loops. Do I have to live with that, or are there any tricks / hints? - I can't use lambdas for the adapters. - transformed expects a result_type that also lambda::res<> doesn't seem to provide. - filtered tries to copy the functor, which in turn lambda doesn't seem to like. Rgds Richard

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Boost.stringalgo
by Marcia Chadly 28 Oct '09

28 Oct '09

Compiling the folowing using is_iless as the predicate for a multi index container results in errors. When is_less is used instead, it compiles fine. typedef mi::multi_index_container< GTLayer, mi::indexed_by< mi::sequenced<>, // list-like index mi::ordered_unique< mi::tag<name>, mi::const_mem_fun<GTLayer, std::string, &GTLayer::GetLayerName>, //std::greater<std::string> ::boost::algorithm::is_iless // names sorted > > > layer_container; The error messages are - Error 4 error C2440: 'type cast' : cannot convert from 'std::basic_string<_Elem,_Traits,_Ax>' to 'unsigned char' C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale 561 Error 3 error C2440: 'type cast' : cannot convert from 'unsigned char' to 'std::basic_string<_Elem,_Traits,_Ax>' C:\Program Files\Microsoft Visual Studio 8\VC\include\xlocale 583 Is this an include problem? I have tried the following includes - #include <boost/multi_index_container.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/sequenced_index.hpp> #include <boost/algorithm/string/compare.hpp> #include <boost/algorithm/string.hpp> #include <boost/algorithm/string/predicate.hpp> #include <map> #include <string> #include <cwchar> #include <locale> Thanks - Marcia

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Serialization, seg fault on "unregister key"
by dada＠lamef.bordeaux.ensam.fr 28 Oct '09

28 Oct '09

Hi, I'm using boost serialization. My program crash with a segmentation fault just before its end. A gdb's backtrace show that the last function's call is the unregister_key()'s function of boost serialization. Is there a way to fix it ? Thank you, Damien.

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[bind] Unable to pass method to simple function pointer
by Carlos 28 Oct '09

28 Oct '09

Hello, I am trying to make a wrapper for libxml's SAX api, for learning purpose, I am trying to use bind to wrap sax events in a class like this : namespace sax { class document { public: document(); ~document(); protected: virtual void start_node( void *user_data, const xmlChar *name, const xmlChar **attrs ); xmlSAXHandler m_evhdl; xmlParserCtxtPtr m_ctxt; }; } The start_node() function is intended to be pointed by the startElement member from xmlSAXHandler ( it has same definition than start_node ). I tried to use bind to copy function pointer in the constructor like this : document::document() { // binding here m_evhdl.startElement = boost::bind( &document::start_node, this, _1, _2, _3 ); // xml init m_ctxt = xmlCreateFileParserCtxt( "catalogue.xml" ); m_ctxt->sax = &m_evhdl; xmlParseDocument( m_ctxt ); } The issue is that I can't submit the binded function to startElement because bind submits "this" as a parameter to startElement, which is incompatible definition, so is there a solution to my binding ? Regards Carlos

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Problem with weak_ptr exception
by Jacob Carlborg 28 Oct '09

28 Oct '09

I'm having some problems with bad_weak_ptr exceptions. I have reduced my code into this test case: #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> using boost::shared_ptr; using boost::weak_ptr; class A { weak_ptr<A> weakThis; public: virtual ~A(){} shared_ptr<A> a; shared_ptr<A> getThis () { shared_ptr<A> x(weakThis); return x; } void init () { a = getThis(); } static shared_ptr<A> create () { shared_ptr<A> x(new A); x->weakThis = x; x->init(); return x; } }; class B : public A { weak_ptr weakThis; public: virtual ~B(){} shared_ptr getThis () { shared_ptr b(weakThis); return b; } static shared_ptr create () { shared_ptr x(new B); x->weakThis = x; x->init(); return x; } }; int main (char** argv, int argc) { shared_ptr b = B::create(); return 0; } If I create an instance of A instead of B or doesn't call x->init() in the B's create function I don't get an exception. The problem is creating a shared_ptr from the weak_ptr in getThis.

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[statechart] Added triggering_event() to the trunk (will be in 1.42 release)
by Andreas Huber 28 Oct '09

28 Oct '09

Those in urgent need of this feature can get it from the trunk. Documentation isn't there yet, but the test should give you a pretty good idea of what it does: <http://svn.boost.org/svn/boost/trunk/libs/statechart/test/TriggeringEventTe…> As always, feedback is highly welcome. Regards, -- Andreas Huber When replying by private email, please remove the words spam and trap from the address shown in the header.

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BGL: cutting subgraph using more than one condition.
by Arman Khalatyan 28 Oct '09

28 Oct '09

Hello, I would like to cut my MST graph using several conditions on Edge. template<typename WMap> class Remover { public: Remover(const WMap& weights, MyFloat threshold) : m_weights(weights), m_threshold(threshold) {} template<typename ED> bool operator()(ED w) const { return m_weights[w] < m_threshold; }// here I would like to have set of conditions based on vertexes of the edge private: const WMap& m_weights; MyFloat m_threshold; }; Remover<weight_map_type> r(get(edge_weight, graphMST), Wthr ); remove_edge_if(r, graphMST); Is it possible to define instead of Wthr to define an array of properties? What is the proper way to do it? Thanks Arman.

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[Boost.Assign][doc] Question on a statement in the documentation
by Alexander Gutenev 28 Oct '09

28 Oct '09

Here http://www.boost.org/doc/libs/1_40_0/libs/assign/doc/index.html#extensions is stated "it is illegal to take the address of a function in the standard library" Is it correct? Where is it mentioned in the Standard? 17.4.4.4/2 says that a member function may be replaced with the version with other signature, but a) "a member function" != "a function" b) May be replaced with the version with other signature doesn't mean one cannot take its address, it only means taking its address doesn't make sense for portable code.

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system error 22
by pedro chaparro 28 Oct '09

28 Oct '09

hi, im trying the serialization examples in http://www.boost.org/doc/libs/1_40_0/doc/html/boost_asio/examples.html , the fact is that i'm getting and invalid argument error, i have examined deeply the code, and i found that the error comes from handle_read function in client.cpp which receive in its function parameter a system::error "e" that is equal to system 22; what is this error related with? thanks --

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[iterator] Automatic definition of transform_iterator reference_type
by Sebastian Theophil 28 Oct '09

28 Oct '09

[Posted once again with better subject] I've encountered a problem when using boost::mem_fn in transform_iterators. In the attached example, I've chained two transform_iterators. The first iterator returns an Obj by value and the second extracts a member of the temporary object. The example shows that the return value is not quite what is expected. boost::mem_fn(&Obj::m_member) returns an int const&. The transform_iterator uses the return value of the UnaryFunction template parameter to initialize his value_type. In the given example, this logic seems too simple. At least if the UnaryFunction is of type boost::_mfi::dm the transform_iterator could do better: If Reference is boost::use_default If UnaryFunction is boost::_mfi::dm && Iterator::value_type is not a reference itself reference = boost::remove_reference( result_of(UnaryFunction) ) Else reference = result_of(UnaryFunction) Else reference = Reference Is this too much of a special case to fix it in the transform_iterator? The same logic would apply to all (unknown) functors that returned references to member variables. In general, the transform_iterator can probably not decide if a reference returned from a UnaryFunction will cease to exist when the temporary is destroyed. It could have been a global object. On the other hand, transform_iterators should work correctly if only boost objects are used, shouldn't they? I'd like to hear what you think, Sebastian #include "boost/iterator/transform_iterator.hpp" #include <vector> struct Obj { Obj(int n) : m_member(n) {} Obj(Obj const& obj) : m_member(obj.m_member) {} ~Obj() { m_member=INT_MIN; } int m_member; }; static Obj GetObjByValue( int n ) { return Obj(n); } void main() { std::vector<int> v(1, 5); int n=*boost::make_transform_iterator( boost::make_transform_iterator( v.begin(), GetObjByValue ), boost::mem_fn(&Obj::m_member) ); _ASSERT(n==INT_MIN); } -- Sebastian Theophil . stheophil(a)think-cell.com Software Engineer think-cell Software GmbH . Invalidenstr. 34 . 10115 Berlin, Germany http://www.think-cell.com . phone +49-30-666473-10 . toll-free (US) +1-800-891-8091 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl . Amtsgericht Berlin-Charlottenburg, HRB 85229

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