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[PP] comma in macro expansions
by Marc Mutz 11 Mar '06

11 Mar '06

Hi, I'm having a problem with "free" commas in macro expansions. I want to generate some function declarations (and implementations) from a user-supplied BOOST_PP_SEQ. The function declarations use enable_if to switch between two sets of interfaces based on the type that shall be returned. Nevermind the details, I've just used a trivial enabling condition here, the error is the same as when using mpl::contains<sometype, Type> in the real code. I've stripped the problem down and attached a test file, complete with my documented attempts to delay expansion of the comma somehow. The preprocessor succeeds when the enable_if or it's two template args are put into (parentheses), but this is no longer valid C++, of course. I guess I'm missing something, but I'm at the end of my Latin, as we say in Germany. Thanks, Marc -- Marc Mutz -- marc(a)klaralvdalens-datakonsult.se, mutz(a)kde.org Klarälvdalens Datakonsult AB, Platform-independent software solutions

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boost::lambda question
by Robert Caldecott 11 Mar '06

11 Mar '06

OK, I'm a bit of a boost noob. I have a container of std::wstring's and I want to use a lambda expression in a for_each loop to pass each string to a WinAPI function - however, I need access to the c_str() method, and this is giving me a problem. For example, if I want to use the DeleteFile WinAPI call, I want to write something like: std::vector<std::wstring> v; ... for_each(v.begin(), v.end(), ::DeleteFile(_1)); But the above won't work as I need to pass the 'C' string to ::DeleteFile. So, I really want to be able to do something like this: for_each(v.begin(), v.end(), ::DeleteFile(_1.c_str())); Any ideas how I can access a member function (like c_str()) using a lambda placeholder?

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Re: [Boost-users] boost::lambda question
by Nat Goodspeed 11 Mar '06

11 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Rob Caldecott > Sent: Saturday, March 11, 2006 12:36 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] boost::lambda question > > Thanks Sebastian, but I am still struggling to make this work. I now get > the following error: > > "error C2664: 'DeleteFileW' : cannot convert parameter 1 from 'const > boost::lambda::lambda_functor<T>' to 'LPCWSTR'" [Nat] Don't you have to bind DeleteFileW as well? Something like (untested): for_each(v.begin(), v.end(), bind(::DeleteFileW, bind(&wstring::c_str, _1))); I think this phrasing should work with either boost::lambda::bind or boost::bind.

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multi_index 1.33.0, known problems with RHEL 3 compiler (gcc 3.2.3)?
by bert hubert 11 Mar '06

11 Mar '06

Hi, Let me start off by saying that I consider multi_index to be the most stunningly clever AND useful piece of c++ around. Thanks! A PowerDNS user on RHEL 3 with a gcc that calls itself 'gcc 3.2.3' reports the following error compiling PowerDNS snapshot 576 (http://svn.powerdns.com/snapshots/576/pdns-2.9.20.20060311.576.tar.gz) Message: http://mailman.powerdns.com/pipermail/pdns-users/2006-March/003134.html mtasker.cc: In member function `bool MTasker<EventKey, EventVal>::schedule() [with EventKey = PacketID, EventVal = std::string]': pdns_recursor.cc:723: instantiated from here mtasker.cc:286: no matching function for call to `boost::multi_index::multi_index_container<MTasker<PacketID, std::string>::Waiter, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::member<MTasker<PacketID, std::string>::Waiter, PacketID, &MTasker<PacketID, std::string>::Waiter::key>, mpl_::na, mpl_::na>, boost::multi_index::ordered_non_unique<boost::multi_index::tag<MTasker<PacketID, std::string>::KeyTag, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, boost::multi_index::member<MTasker<PacketID, std::string>::Waiter, time_t, &MTasker<PacketID, std::string>::Waiter::ttd>, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<MTasker<PacketID, std::string>::Waiter> >::get()' make[3]: *** [pdns_recursor.o] Error 1 make[3]: Leaving directory /temp/pdns-2.9.20.20060311.576/pdns' To reproduce, download the tar file, run ./configure --with-modules="" ; cd pdns ; make pdns_recursor, besides boost there are no dependencies when compiled like this. Relevant details from mtasker.hh http://wiki.powerdns.com/projects/trac/browser/trunk/pdns/pdns/mtasker.cc?r… 60 struct KeyTag {}; 61 typedef multi_index_container< 62 Waiter, 63 indexed_by < 64 ordered_unique<member<Waiter,EventKey,&Waiter::key> >, 65 ordered_non_unique<tag<KeyTag>, member<Waiter,time_t,&Waiter::ttd> > 66 > 67 > waiters_t; 68 69 waiters_t d_waiters; >From mtasker.cc: http://wiki.powerdns.com/projects/trac/browser/trunk/pdns/pdns/mtasker.hh?r… 285 typedef typename waiters_t::template index<KeyTag>::type waiters_by_ttd_index_t; 286 waiters_by_ttd_index_t& ttdindex=d_waiters.get<KeyTag>(); Any ideas, especially on a workaround? It compiles fine on all gcc's I have access to. Thanks! -- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services

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Books on/using Boost
by Scott Meyers 11 Mar '06

11 Mar '06

I'm interested in books on or making significant use of Boost. Books on Boost include those on the BGL and the MPL, plus Karlsson's overview of Boost. Are there others? The only book I know of that makes extensive use of Boost is "C++ Cookbook" by D. Ryan Stephens et al. from O'Reilly. Are there others? Thanks, Scott

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[serialization] Creating new archives derived from polymorphic archive
by Robert S. Grimes 11 Mar '06

11 Mar '06

Hi, How do I get started? I want to create a set of custom archives that include such features as a small header, CRC, digital signatures, etc. I want to put this into a DLL, so I want to go the polymorphic route. There are directions for creating new archives from the template versions, but not for the polymorphic versions. I'm not sure the starting point is the same, so I thought I'd ask first, as this is stretching my abilities a bit. Thanks, -Bob

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Re: [Boost-users] Syntax of get for Variant and any_cast for Any
by Sohail Somani 10 Mar '06

10 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Scott Meyers > Sent: Friday, March 10, 2006 2:04 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] Syntax of get for Variant and > any_cast for Any > My only other knowledge of "get" is from tuple, where "get" > takes a compile-time > constant, not a type, as an argument. With that background, > I found the use of > "get" for variant initially confusing. I think it'd be > better to find a name > with the "_cast" suffix and to explicitly specify pointer and > reference types > (as with dynamic_cast) and adopt that convention. I don't > know enough about the > various Boost libraries to know whether that is a reasonable > suggestion. I think shared_ptr has dynamic_pointer_cast or something. This is much easier to read than get

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[BGL] graph copy after Kruskal's algorithm?
by Alejandro Aragón 10 Mar '06

10 Mar '06

Hi all, After running Kruskal's algorithm I end up with the list of the edges that form the minimum cost. However, no new graph is created. I need the resulting graph for further computations. How do you create a graph from an existing one but only selecting the edges contained in the minimum spanning tree vector? I've seen that there are some functions to accomplish this but I couldn't find any example of how to do it: template <class EdgeIterator, class EdgePropertyIterator> adjacency_list(EdgeIterator first, EdgeIterator last, EdgePropertyIterator ep_iter, vertices_size_type n, vertices_size_type m = 0, const GraphProperty& p = GraphProperty()) The existing graph has properties in edges and vertices that I also need to keep. Can anyone help? Thank you all, A.Aragon

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Re: [Boost-users] Help needed with random exponential_distribution
by dahaverk＠rockwellcollins.com 10 Mar '06

10 Mar '06

It seems my problem is with the rand48 function. With Boost_1_29_0 ---> sizeof(boost::rand48)=8 e.g. the size of a double. With Boost_1_33_1 ---> sizeof(boost::rand48)=16 e.g. twice the size of a double. Because of the truncation that happened with the boost_1_29_0 We were seeing a correctly randomized distribution for the exponential_distribution. Is this a config problem? If so, where do I fix the "boost::rand48" to be a "double" again? I did run the boost ./configure on the Boost_1_33_1 directory before I started using it on the Sun Sparc Solaris8 machine. Thanks, Dave

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Boost Statechart: general questionss about what the library can do
by RIVASSEAU Jean Noel 10 Mar '06

10 Mar '06

Hi there, I am almost entirely new to state machines, finite automata (by almost I mean that I know the concept and very little of the theory). However I need to evaluate if the Boost library can meet the requirements of a project I plan to use it on. Basically I have two questions: First and most important: Is it possible to *ask* the state machine to go from a state A to a state B *automatically* ?? I mean, I am in state A. I need to go to State B, but I cannot go straight from A to B, I must go first through state C, D, E and finally B for example. Can the library automatically compute a path and generate the correct transitions (event)?? If it is not possible, I would like to know if it is a fundamental problem (theorical with state automata, common to any library implementation) or just something that Boost Statechart does not provide, but other implementations could. Note that it is not necessarily for me that the automata computes the "best" or "shortest" path (set of transitions) it must just generate correct transitions that I can log. My second question is easier, more implementation related, and I think the answer is yes, but anyway: When a transition is executed (automatically, or explicitely), can I call a function? That is, when an event is processed, can I implement some code that will be executed each time an event is processed ? Thank you!! Jean-Noël Ps: Is this the correct place to discuss Boost Statechart, since it is not yet part of the official Boost package (distribution) ?

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