October 2007 - Boost-users - lists.preview.boost.org

[optional] documentation errors
by Edward Diener 16 Oct '07

16 Oct '07

In the 1.34.1 documentation for optional<T>, in the Synopsis section, it is currently written: -------------------------------------------------------------------------- template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; template<class TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ; AND template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; template<class TypedInPlaceFactory> optional& operator = ( TypedInPlaceFactory const& f ) ; -------------------------------------------------------------------------- Since InPlacefactory and TypedInPlacePlactory are actual classes, these should be: template<InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; template<TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ; AND template<InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; template<TypedInPlaceFactory> optional& operator = ( TypedInPlaceFactory const& f ) ; ------------------------------------------------------------------------- In the Detailed Semantics these are shown correctly.

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[fusion] subset view
by Chris Weed 16 Oct '07

16 Oct '07

Hi, I would like to make a subset view of the element in a tuple. It would, for example, give me a view into the first, third, and fifth element of the tuple. It isn't clear how to do this with the available views. Thanks, Chris

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[serialization]-- serialize binary data to a memory buffer?
by Rich Peters 16 Oct '07

16 Oct '07

I saw an example where boost serialized a text archive to a strstream for sending via a socket. I would like to do something similar, but for binary data. Is there a way to do the binary serialization to a memory buffer, and then send it elsewhere? It doesnt seem like strstream and boost::archive::binary_oarchive would mix correctly. I have also seen some discussion regarding a binary_iostreams library, but its doesnt look like that exists yet. thanks Rich

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Re: [Boost-users] [continued][boost::fusion v2 and xpressive] versioning conflicts...
by Ovanes Markarian 16 Oct '07

16 Oct '07

Eric, I changed the files. Should I zip them and post via mailinglist? Or should I submit them somewhere else? List of files which were changed: detail/core/linker.hpp detail/core/matcher/alternate_matcher.hpp detail/static/productions/alt_compilers.hpp detail/utility/any.hpp detail/utility/cons.hpp proto/op_base.hpp proto/proto_fwd.hpp xpressive.hpp One problem is that xpressive.hpp has info about boost version, but this is the mostly used file for inclusion. Therefore I believe this check fill fail even in boost 1.35: #if BOOST_VERSION >= 103500 # ifndef BOOST_XPRESSIVE_FUSION_V2 # define BOOST_XPRESSIVE_FUSION_V2 # endif //BOOST_XPRESSIVE_FUSION_V2 #endif //BOOST_VERSION I also executed your examples from the boost/lib directory and they produced in both cases same results. Your answer today is highly appreciated, since I will be on vacation from tomorrow on. thanks, Ovanes > On 9/24/07, Ovanes Markarian < om_boost(a)keywallet.com> wrote: > > > > Eric, > > > > sorry for the delay. I only now found some time to work on that issue: > > http://lists.boost.org/boost-users/2007/08/30120.php > > > > > > After analysing your post and investigation what's going on, I would > > like to write my opinion: > > > > changing xpressive_fwd.hpp or proto_fwd.will not help. > > > > I grepped where fusion includes are used and need to enclose these in > > some conditional statements: > > > > #ifdef BOOST_XPRESSIVE_FUSION_V2 > > # include ... //fusion 2 headers > > #else > > # include ... // fusion 1 headers > > #endif > > > > Actually this can be done using some kind of a macro function like: > > > > #include BOOST_XPRESSIVE_FUSION_ROOT(sequence/cons.hpp) > > ... > > > > The macro function will deliver the root dependent on the predefined > > macros like: > > 1. if !defined XPRESSIVE_FUSION_ROOT and use V2 > > => choose the root for V2 > > else => choose the root for V1 > > > > As I found out the following files need to be changed: > > linker.hpp > > alternate_matcher.hpp > > alt_compilers.hpp > > any.hpp > > cons.hpp > > arg_traits.hpp > > op_base.hpp > > proto_fwd.hpp > > > > If you give me your green light I will do it and submit a patch. > > > > > > With Kind Regards, > > Ovanes > > > > > >

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Problem using Boost Graph Library - Python Bindings
by Camilo La Rota 16 Oct '07

16 Oct '07

Hello all, I have just installed the Boost Graph Library - Python Bindings. Everything seemed to be ok, I can read a graph from the example "mst.dot" file and from my own ".dot" files, I can write them back to a file. However, when I try the example script (at the end of the following page: http://www.osl.iu.edu/~dgregor/bgl-python/), -------------------------------------------------------------------- import boost.graph as bgl # Load a graph from the GraphViz file 'mst.dot' graph = bgl.Graph.read_graphviz('mst.dot') # Convert the weight into floating-point values weight = graph.convert_property_map(graph.edge_properties['weight'], 'float') ... etc ------------------------------------------------------------------- it stops at the third line with the following error: ---------------------------------------------------------------------------- Traceback (most recent call last): File "<pyshell#17>", line 1, in <module> weight = graph.convert_property_map(graph.edge_properties['weight'],'float') KeyError: 'weight' ------------------------------------------------------------------------ I receive the same error message if I write only: graph.edge_properties['weight'] The content of the example mst.dot file is: -------------------------------------------------- graph G { A -- C [weight="1.0"] B -- D [weight="1.0"] B -- E [weight="2.0"] C -- B [weight="7.0"] C -- D [weight="3.0"] D -- E [weight="1.0"] E -- A [weight="1.0"] E -- B [weight="1.0"] } -------------------------------------------------- Does any one have any idea about the source of this error. Thanks a lot in advance, Camilo

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Re: [Boost-users] How to add a type to is_arithmetic
by Chad Walters 16 Oct '07

16 Oct '07

It's not entirely clear from your description if you really need to have is_arithmetic be true for your fixed_point class or if you just want to have some predicate that is true for both the built-in arithmetic types and your fixed_point class. If the former, then you will likely run afoul of problems, for the reasons previously pointed out. Hopefully it is the latter - in which case you should just define your own predicate with the appropriate logic (true for fixed_point or is_arithmetic types). Chad

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Retrieve number os affected rows
by Hamilton Vera 16 Oct '07

16 Oct '07

How to retrieve the number of affected rows after an update? ( I am testing in a MySQL database) I only found this in the list; http://lists.boost.org/Archives/boost/2006/12/114037.php But I was unable to find the sql.rowsaffected() fuction. I am using soci version 2.2.0. -- Hamilton Vera int Administrator (char Network[],char ComputationalSystems[]); Seven Internet http://lib.seven.com.br "Google is my shepherd, no want shall I know"

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[xpressive] crash...
by Ovanes Markarian 16 Oct '07

16 Oct '07

Hello Eric, this code fragment will crash, since 'what' uses iterators into the invalid string x::smatch what; if(x::regex_match(std::string(" (some_type_ptr) xyz,"), what, regex)) //string goes out of scope after this sentance { std::cout << what[0] << endl; // boom! string iterators are no longer valid std::cout << what[1] << endl; } May be there is a way to probit this kind of behaviour during the compilation or at least this can be stated in the docs... With Kind Regards, Ovanes

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[system] in multi-threaded context
by Jeroen van der Wulp 16 Oct '07

16 Oct '07

Hello, I have some problems with the latest changes to asio, which turn out to be caused by problems with boost::system. The newer versions of boost::asio now use boost::error_code provided by boost::system for error handling. On OS X 10.4 with XCode 2.4.1 comparing two boost::error_code objects e1 & e2 always returns false. I believe this is caused by comparing objects accross threads. But this is just a guess. A problem I noticed on with Apple's version of gcc is that static instance variables behave strange, there seems to be a copy for each variable in each compilation unit that uses them? This may also somehow be the cause for my problems with boost::system. Another problem is that when I receive an error_code object, say e, from asio, trying to print e.message() fails with an access violation. This happens on Windows, Linux, OS X. What am I doing wrong? Thanks, Jeroen van der Wulp

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[boost-users] enable_if and checking if class derives from boost::operators does not work.
by chun ping wang 16 Oct '07

16 Oct '07

namespace boost { template <class T, class U> char (& is_op_test(boost::operators<T,U> const&) )[2]; template <class T> char is_op_test(T const&); template<class T> T const& make(); template <class T> struct is_operators : boost::mpl::bool_<(sizeof(is_op_test(make<T>())) == 2)> {}; } and this function declaration. template <typename T, template <typename ELEM, typename = std::allocator<ELEM> > class CONT > typename boost::enable_if<boost::mpl::or_<boost::is_integral<T>, boost:: is_operators<T> >, CONT<T> >::type primelist(const T& MAX_BOUND, const T& K, boost::function<bool(const T&, const T&)> f); BigInteger class declaration looks like this.. class BigInteger : public BigUnsigned, boost::operators<BigInteger>, boost::operators<BigInteger, int> { }; I compile with T = int and it works. When i compile with T = BigInteger I get the following errors. on visual c++. error C2770: invalid explicit template argument(s) for 'boost::enable_if<boost::mpl::or_<boost::is_integral<T>,boost::is_operators<T> >,CONT<T>>::type primelist(const T &,const T &,boost::function<bool(const T &,const T &)>)' ./cs512/c++/primeMain.cpp(24) : see declaration of 'primelist'" on mingw dev-cpp i get this error. unable to find function.... In both cases passing BigInteger does not work. thanks for the help. BigInteger does derive from boost::operators and theirs two overload.

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