April 2005 - Boost-users - lists.preview.boost.org

BGL::johnson_all_pairs_shortest_path question
by Andreas Fabri 28 Apr '05

28 Apr '05

Hello, What is the non-named parameter version of this algorithm. In the online manual it says Weight (and this is probably a typo, as there is a template parameter WeightMap). Also what are the arguments id1 and zero good for? andreas

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[BGL] check edge existence in adjacency_matrix in constant time?
by Felipe Magno de Almeida 28 Apr '05

28 Apr '05

Sorry if I have overlooked something in the docs, but Im really not finding it... Is there someway to check the existence of an edge in adjacency_matrix in constant time knowing its vertices? An explanation or a pointer to the right place in the docs would be really appreciated. Thanks in advance, -- Felipe Magno de Almeida UIN: 2113442 email: felipe.almeida at ic unicamp br, felipe.m.almeida at gmail com, felipe at synergy com I am a C, modern C++, MFC, ODBC, Windows Services, MAPI developer from synergy, and Computer Science student from State University of Campinas(UNICAMP). To know more about: Unicamp: http://www.ic.unicamp.br Synergy: http://www.synergy.com.br current work: http://www.mintercept.com "There is no dark side of the moon really. Matter of fact it's all dark."

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Re: [Boost-users] Compatibility between shared_ptr and Rational RoseRT
by Dave.Ware＠seleniacomms.com 28 Apr '05

28 Apr '05

Don't worry about having hijacked my original thread. The examples you've been discussing have been very helpful to my code as well. We haven't solved all of our problems yet, but it is much better. Thanks ------------------------------------------------------------ This email and any attached files contains company confidential information which may be legally privileged. It is intended only for the person(s) or entity to which it is addressed and solely for the purposes set forth therein. If you are not the intended recipient or have received this email in error please notify the sender by return, delete it from your system and destroy any local copies. It is strictly forbidden to use the information in this email including any attachment or part thereof including copying, disclosing, distributing, amending or using for any other purpose. In addition the sender excludes all liabilities (whether tortious or common law) for damage or breach arising or related to this email including but not limited to viruses and libel.

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Function pointers, result_of<> and function_traits<>
by Delfin Rojas 27 Apr '05

27 Apr '05

Hello all, I am trying to get the return type of a member function given its signature. Consider the following example from the boost result_of test: struct X {}; int main { using namespace boost; typedef int (X::*mem_func_ptr)(float); BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr(X,char)>::type, int>::value)); } This test compiles/runs with no problems. Now, what I want is the return type of a function with signature "int (X::*)()" I added the following to the test: typedef int (X::*empty_mem_func_ptr)(); BOOST_STATIC_ASSERT((is_same<result_of<empty_mem_func_ptr(X)>::type, int>::value)); This does not compile. I get an error boost_1_32_0\boost\utility\result_of.hpp(43) : error C2825: 'F::template': cannot form a qualified name. I tried to do this same thing with function_traits but it seems function traits does not support member function pointers at all. So this is all I have. If somebody can help me I would appreciate it. Thanks -delfin

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const-correctness and lambda expression
by Matthias Kaeppler 27 Apr '05

27 Apr '05

Hi, in my program, I have this function to compute the sum of sizes of a bunch of files: Glib::ustring DirBrowser::get_total_file_size() { using namespace boostfs; // boostfs = boost::filesystem using namespace lambda; // lambda = boost::lambda boost::intmax_t sum = 0; std::for_each(m_first_file,m_files.end(),sum+=bind(&file_size,*_1)); return make_size_human_readable( sum ); } The line with for_each computes the sum of file sizes, by iterating over a container of pointers to boostfs::pathS, starting at the first file (there are also directories, before the files), till the end, invoking the lambda functor on each. Since this method does not change the state of the object, I wanted to declare it const, but suddenly the lambda expression starts complaining: Somehow, those path objects inside the lambda expression become const now, too, and it doesn't compile anymore. How come? -- Matthias Kaeppler

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RE: [Boost-users] Problems with boost::filesystem::path continued
by Johnson, Donald W MVK Contractor 27 Apr '05

27 Apr '05

It seem that due to sheer luck mixing the runtimes was not causing problems. Objects allocated in the dll where always deleted in the dll and objects allocated in the application likewise deallocated in the application. I know because I had forced things to work using BOOST_FILESYSTEM_NO_LIB and manually linking to the library, and the application worked and all the tests ran fine. The application was linked to /MT or /MTd so that was a disaster waiting to happen the first time I called a function across dll with a dynamicly allocated argument that was held and eventually dealocated on the dll side. I was being saved because that particular situation never occurs. Thanks for the help I thought the error message was refering to the runtime that boost itself was linking against, so was trying to find how to make boost link against the dynamic library. Thanks Donald J -----Original Message----- From: John Maddock [mailto:john@johnmaddock.co.uk] Sent: Wednesday, April 27, 2005 4:44 AM To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Problems with boost::filesystem::path continued >I found the main problem, I had edited the wrong boost/config/user.hpp >file. > When I set BOOST_FILESYSTEM_DYN_LINK in the correct user.hpp file I >get this error. > > c:\Boost\include\boost-1_31\boost\config\auto_link.hpp(269): fatal > error > C1189: #error : "Mixing a dll boost library with a static runtime is > a really bad idea..." > > #if (defined(_DLL) || defined(_RTLDLL)) && defined(BOOST_DYN_LINK) # > define BOOST_LIB_PREFIX #elif defined(BOOST_DYN_LINK) # error "Mixing > a dll boost library with a static runtime is a really bad idea..." > #else > # define BOOST_LIB_PREFIX "lib" > #endif > > So wher am I supposed to set the _DLL symbol or do I need to disable > auto_link. If so how? The message tells you what you've done wrong: you can not use a dll that passes C++ objects between itself and your application unless you are also using a dll runtime library. If you do manage to do this your code will very likely crash and burn at runtime (due to recourses being allocated and freed by differing C++ runtimes). If you switch your code generation options (in the VC++ IDE) to use a dll runtime then the error message will go away. John.

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minimal perfect hash
by Davi de Castro Reis 27 Apr '05

27 Apr '05

Hi all, I recently found in the archives a discussion about minimal perfect hashing in boost, in the beginning of January (2005). Does someone one have any news about it? I have written myself a F/OSS C library for minimal perfect hashing, and I am willing to contribute for any efforts to make this data structure part of the boost toolkit. Thanks in advance, Davi

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Re: Placeholder Arguments
by Joe McCay 27 Apr '05

27 Apr '05

David Abrahams <dave(a)boost-consulting.com> writes: > Are you asking about runtime lambda expressions as in the Boost Lambda > library, or compile-time lambda expressions as in MPL? > > -- > Dave Abrahams > Boost Consulting > www.boost-consulting.com I was talking about MPL because that is the only one I have studied at the moment. What is the difference between the two outside of the obvious runtime/compile-time difference? I was trying to figure out how a particular placeholder gets its arguments to choose from when deciding the argument (argument 1 for _1 etc.). Thank you. Joseph L. McCay

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Re: Boost Logging Library?
by Jwahar Bammi 27 Apr '05

27 Apr '05

I dont understand the need for the "Proposed Boost logging library". A perfectly good and flexible logging library exists in the form of log4cxx, which is much more flexible than the proposal, has a ton of tools, appenders, is compatible with log4j/log4net etc etc (for those of us who live in multiple worlds). log4cxx is going through a almost complete rewrite, but is still eminently usable. see http://logging.apache.org/log4cxx/ cheers, > > >Vladimir Prus wrote: > > >>Hi Matthias, >> >> >> >> >>>on http://www.torjo.com/ is a "Boost logging library" available for >>>download, but it doesn't exist on the official boost website. >>> >>>Will this library be in a future release of boost, or has someone just >>>abused the well-known name for pushing his work? >>> >>>A logging library would be a very nice thing to have in boost, but >>>before I use this one, I want to make sure it will be available publicly >>>in the official boost packages. >>> >>> >>This library was not reviewed, and I'm not sure if the review was requested. >>So, it's "Proposed Boost logging library", and is not an official part of >>Boost. >> >> >>- Volodya >> >> > >In fact, John Torjo has requested a formal review at boost.devel just >today, see his post at >http://article.gmane.org/gmane.comp.lib.boost.devel/122414 > >- Andreas > > -- Jwahar Bammi bammi(a)memento-inc.com

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Problems with boost::filesystem::path continued
by Johnson, Donald W MVK Contractor 27 Apr '05

27 Apr '05

I found the main problem, I had edited the wrong boost/config/user.hpp file. When I set BOOST_FILESYSTEM_DYN_LINK in the correct user.hpp file I get this error. c:\Boost\include\boost-1_31\boost\config\auto_link.hpp(269): fatal error C1189: #error : "Mixing a dll boost library with a static runtime is a really bad idea..." #if (defined(_DLL) || defined(_RTLDLL)) && defined(BOOST_DYN_LINK) # define BOOST_LIB_PREFIX #elif defined(BOOST_DYN_LINK) # error "Mixing a dll boost library with a static runtime is a really bad idea..." #else # define BOOST_LIB_PREFIX "lib" #endif So wher am I supposed to set the _DLL symbol or do I need to disable auto_link. If so how? Thanks, Donald Johnson

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