February 2010 - Boost-users

generate structs with all combinations of members from a given struct
by Hicham Mouline 14 Feb '10

14 Feb '10

Hello, struct params { double field1; double field2; double field3; double fiedl4; }; I would like to generate all the types that hold any combination of the members of params. struct params_field1 { double field1; }; struct params_field2 { double field2; }; struct params_field3 { double field3; }; struct params_field4 { double field4; }; struct params_field1_field2 { double field1; double field2; }; struct params_field1_field3 { double field1; double field3; }; struct params_field1_field4 { double field1; double field4; }; struct params_field2_field3 { double field2; double field3; }; struct params_field2_field4 { double field2; double field4; }; struct params_field3_field4 { double field3; double field4; }; struct params_field1_field2_field3 { double field1; double field2; double field3; }; struct params_field1_field2_field4 { double field1; double field2; double field4; }; struct params_field1_field3_field4 { double field1; double field3; double field4; }; struct params_field2_field3_field4 { double field2; double field3; double field4; }; struct params_field1_field2_field3_field4 { double field1; double field2; double field3; double field4; }; There are 15 of these, which is 2^4 -1, where 4 is the number of members in params. Assuming params is adapted as a fusion sequence, this looks doable with PP? Should I be looking at BOOST_PP_LIST_FOLD_xxx macros? regards,

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[Function] Takes functor by value not reference?
by Alexander Lamaison 14 Feb '10

14 Feb '10

I may be misunderstanding as the boost::function code is tricky to follow but it seems to me that the function contructor takes the functor it is passed by value rather than by reference. This requires the functor to be copyable. In my case I'm trying to pass a functor as its abstract supertype which prevents copying. Is it not possible to take the functor my reference, thereby removing the need for copying? The constructor in question appears in function_template.hpp at line 1056 in version 1.40.0: Summarised: template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS> class function<BOOST_FUNCTION_PARTIAL_SPEC> : public BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS> { typedef BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS> base_type; template<typename Functor> function(Functor f) : base_type(f) { } } Many thanks. Alex Lamaison -- http://swish.sourceforge.net

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Re: [Boost-users] [random] number generator as static class member
by Moritz Beber 14 Feb '10

14 Feb '10

(I'm sorry for creating a new message in reply but I don't get my own messages.) The problem was of course the uniform_01 distribution which uses the underlying generator by value rather than reference. I now tie in a uniform_real in the same interval and it works just fine. Enjoy the rest of the weekend, Moritz

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[Function] Overloaded functor as a boost::function
by Alexander Lamaison 14 Feb '10

14 Feb '10

I'm trying to pass a function with an overloaded operator() to a function expecting a boost::function parameter. This fails to compile as it appears to pick the wrong overload. Here is the functor interface with the two ways it can be called: class Command { public: virtual void operator()( const com_ptr<IShellItemArray>& items, const com_ptr<IBindCtx>& bind_ctx); virtual void operator()( const com_ptr<IDataObject>& data_object, const com_ptr<IBindCtx>& bind_ctx); }; When I try to pass an instance of this functor to a method expecting a boost::function of this type: boost::function<void( const com_ptr<IShellItemArray>& items, const com_ptr<IBindCtx>& bind_ctx)> I get a compiler error C2440: '=' : cannot convert from 'IShellItemArray *' to 'IDataObject *'. This seems to indicate that the boost::function is trying to pass its parameters to the second overload rather than the first. Any ideas how I can make boost::function pick the correct overload? I'm using Boost 1.40.0. Many thanks. Alex Lamaison -- http://swish.sourceforge.net

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[random] number generator as static class member
by Moritz Beber 14 Feb '10

14 Feb '10

Dear list users, I have attached a reduced case of what I want to do. Basically, I thought it would be a good idea to have one general number generator that I attach to specific distributions in my member functions according to my needs (uniform_01 in this example, but I also want to use others). So for example I do the following in my real code, where 'rng' is my static member object: typedef boost::lagged_fibonacci607 rand_gen; boost::bernoulli_distribution<double> b_dist(p); boost::variate_generator<rand_gen&, boost::bernoulli_distribution<double> > bool_gen(MyClass::rng, b_dist); boost::uniform_smallint<short unsigned> in_dist(0, this->nodes_in - 1); boost::variate_generator<rand_gen&, boost::uniform_smallint<short unsigned> > in_gen(MyClass::rng, in_dist); Unfortunately, as the code I attached demonstrates, every time I do that the original state of the 'rng' seems to be used. Do you have suggestions for fixing this? Thank you in advance, Moritz

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[boost.asio] Getting/setting RTS and CTS/DSR/DCD with serial_port
by David Faure 13 Feb '10

13 Feb '10

Hello, I'm porting old platform-specific serial port code to use asio::serial_port, and it's working nicely overall, but I'm missing some functionality. How can I get/set the status of the DTR, RTS and DCD pins? This seems to be needed for some devices. I'm no expert, but the current documentation says: // RTS on if Data in Transmit queue or while BREAK transmitted // RTS off iff no data in transmit queue and // Output Handshaking via CTS/DSR/DCD // data is transmitted only when all lines which are enabled for // output handshake are up. (BREAKs can be transmitted) There is also this one, can this be implemented in asio? // setErrorChar ... enable/disable Error handling and lets you define // the error replacement char. // Specifies whether bytes received with parity errors are replaced // with the character specified by the ErrorChar member. void setErrorChar(bool on, char errorChar); If it helps, the Windows implementation was: dcbI.fbFlowReplace |= MODE_ERROR_CHAR; dcbI.bErrorReplacementChar = cError; but I suppose I don't have access to the DCBINFO used inside boost, and anyway the whole purpose is to make this cross-platform :) -- David Faure | dfaure(a)kdab.com | KDE/Qt Senior Software Engineer Klarälvdalens Datakonsult AB, a KDAB Group company Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322) KDAB - Qt Experts - Platform-independent software solutions

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metaprogramming -- does a specialization exist?
by Peter Foelsche 13 Feb '10

13 Feb '10

Is there some way to check at compile time whether a particular specialization exists? E.g. I have a template class with two template arguments which are commutative -- means they can be exchanged and the result is the same. Can I check whether type<A, B> exists and if not select type<B, A>? Peter

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Sun C++ 5.10 and BGL adjacency_list
by Nicholas Brealey 13 Feb '10

13 Feb '10

I am trying to use the Boost Graph Library from Boost 1.42.0 with Sun Studio 12 update 1 but the adjacency_list.cpp example from the libs/graph/example directory does not compile. Does anyoone have a workaround? > $ CC -V > CC: Sun C++ 5.10 SunOS_i386 128229-04 2009/11/25 > Usage: CC [ options ] files. Use 'CC -flags' for details > $ CC -library=stlport4 -features=tmplife -features=tmplrefstatic -I/home/nick/boost_1_42_0 -o adjacency_list adjacency_list.cpp > "/home/nick/boost_1_42_0/boost/graph/detail/adjacency_list.hpp", line 1722: Error: Could not find a match for boost::detail::get_dispatch<boost::detail::Config, boost::detail::Base, boost::detail::Property>(boost::adj_list_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config, boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config>>, unsigned VertexProperties::*, int) needed in boost::get<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undir ectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config, boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config>, unsigned VertexProperties::*>(unsigned VertexProperties::*, boost::adj_list_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config, boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config>>&). > "adjacency_list.cpp", line 63: Where: While instantiating "boost::get<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config, boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config>, unsigned VertexProperties::*>(unsigned VertexProperties::*, boost::adj_list_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, Vertex Properties, EdgeProperties, boost::no_property, boost::listS>::config, boost::undirected_graph_helper<boost::detail::adj_list_gen<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::listS, boost::vecS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>::config>>&)". > "adjacency_list.cpp", line 63: Where: Instantiated from non-template code. > "adjacency_list.cpp", line 71: Warning (Anachronism): Assigning int to boost::detail::error_property_not_found. > "adjacency_list.cpp", line 71: Error: Cannot cast from int to boost::detail::error_property_not_found. > "adjacency_list.cpp", line 82: Error: The operation "std::ostream<<boost::detail::error_property_not_found" is illegal. > "adjacency_list.cpp", line 84: Error: The operation "boost::adj_list_vertex_property_map<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::detail::error_property_not_found, boost::detail::error_property_not_found&, std::string EdgeProperties::*>[boost::detail::edge_desc_impl<boost::undirected_tag, void*>]" is illegal. > "adjacency_list.cpp", line 93: Error: The operation "std::ostream<<boost::detail::error_property_not_found" is illegal. > "adjacency_list.cpp", line 98: Error: The operation "std::ostream<<boost::detail::error_property_not_found" is illegal. > "adjacency_list.cpp", line 100: Error: The operation "boost::adj_list_vertex_property_map<boost::adjacency_list<boost::vecS, boost::listS, boost::undirectedS, VertexProperties, EdgeProperties, boost::no_property, boost::listS>, boost::detail::error_property_not_found, boost::detail::error_property_not_found&, std::string EdgeProperties::*>[boost::detail::edge_desc_impl<boost::undirected_tag, void*>]" is illegal. > 7 Error(s) and 1 Warning(s) detected. I posted a similar question on the Sun C++ forum last year but no one had a solution: http://forums.sun.com/thread.jspa?threadID=5419942 g++ works fine: > $ g++ -I/home/nick/boost_1_42_0 -o adjacency_list adjacency_list.cpp > $ g++ --version > g++ (GCC) 3.4.3 (csl-sol210-3_4-branch+sol_rpath) > Copyright (C) 2004 Free Software Foundation, Inc. > This is free software; see the source for copying conditions. There is NO > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. > Thanks Nick

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Complete vs incomplete (fwd decl'd) types
by Dominique Devienne 12 Feb '10

12 Feb '10

In client code including the header for MyDerived, I'm using a MyPtr<MyDerived>, but the static assert below was failing. It took me a little while to figure out that in myderived.h, the MyDerived::nested_type typedef is using a forward-declared MyNestedDerived type declared in my_nested_derived.h, that the client code was not including, which was the reason is_base_of was failing with the error below (Boost 1.41, VC9). Adding a #include <my_nested_derived.h> fixed it. boost\type_traits\is_base_and_derived.hpp(228) : error C2139: 'MyNestedDerived' : an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_base_of' But is there a way to get a more obvious error message stating that MyNestedDerived is an incomplete type or something? In retrospect the message is not that bad, but I'm hoping there's a better way. Thanks, --DD PS: Of course there's a reason the nested type is in a separate header, and it's an idiom repeated often in our code base. template <class E> class MyPtr { public: ... typedef typename E::nested_type nested_type; explicit MyPtr(const shared_ptr<nested_type>& n) : ... { BOOST_STATIC_ASSERT((is_base_of<MyNestedBase, nested_type>::value)); } ... };

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PP: LOCAL_ITERATE: how to get rid of extra empty lines
by Hicham Mouline 12 Feb '10

12 Feb '10

Hello I get the following preprocessed output # 34 "my_header.hpp" # 1 "/usr/include/boost/preprocessor/iteration/detail/local.hpp" 1 3 4 # 34 "/usr/include/boost/preprocessor/iteration/detail/local.hpp" 3 4 //result of LOCAL_macro expansion //result of macro expansion //result of macro expansion //result of macro expansion How do I get rid of the blank lines in the middle? Regards,

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