January 2011 - Boost-users - lists.preview.boost.org

template type asserting
by Kraus Philipp 25 Jan '11

25 Jan '11

Hello, I have written a template class and I would like tot "assert the type". My class should only use floating point types like double or float. Can I do this check with BOOST_STATIC_ASSERT or anything else? The class need not to use a "countable type" (math: in N). Thanks Phil

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update on boost logger
by Jeff Graham 25 Jan '11

25 Jan '11

Hello everyone, Where can I find the logger that has been accepted into boost? I think it is here: http://boost-log.sourceforge.net/libs/log/doc/html/index.html ? According to this message it was accepted into boost on March 24, 2010, but subject to some critical fixes: http://lists.boost.org/boost-announce/2010/03/0256.php However, the changelog at the above sourceforge site was last updated in May 2010, and the ToDo/wish list seems lengthy. There seems no easy way to track the progress on the critical fixes, some which are performance related and are of concern to my projects. Any status on the fixes, informal review on the fixes, and if all will be done for 1.46? Thanks

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Re: [Boost-users] [Preprocessor] Relative Addresses in BOOST_PP_FILENAME_1
by Hossein Haeri 25 Jan '11

25 Jan '11

Dear TONGARI, > Just make sure "Lib" is in the include path, then everything works fine > for me. So, here is a very strange observation I got after trying to strictly follow the above recommendation of yours: I added my current working directory to the include path and it worked! I always thought that that is already in ones include path (by default). My compilers have always found such files. It even happens that my other files (in the same directory) used to find Header.hpp even despite that strange error I used to get! :O > It would be fine in the Remarks section to add words like:"quoted > filename may not work with some compilers here, such as gcc..." Agree. Thanks a lot, --Hossein

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Re: [Boost-users] [Preprocessor] Relative Addresses in BOOST_PP_FILENAME_1
by Hossein Haeri 25 Jan '11

25 Jan '11

Dear TONGARI, > Where I said <> I meant <something in compiler's include path>, that > works fine, just as Edward and Steven said. Well, my working directory is already in my compiler's include path. And, inside Header.hpp, the following line #define BOOST_PP_FILENAME1 <Header.hpp> fails to compiler in GCC 4.5.1 because GCC says it can't find Header.hpp. And, I am missing anything here? Maybe it's better that you tell me what you'd be writing instead of the line above if it would have been you... > If this is not a bug with a specific compiler, I hope at least it should > be noted in Boost.PP's doc. It's not. Both quote and angle brackets are mentioned to work in the specs: http://www.boost.org/doc/libs/1_45_0/libs/preprocessor/doc/ref/filename_x.h… TIA, --Hossein

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Re: [Boost-users] Boost-users Digest, Vol 2613, Issue 3
by Loek Cleophas 25 Jan '11

25 Jan '11

On Mon, Jan 24, 2011 at 18:00, <boost-users-request(a)lists.boost.org> wrote: > Date: Mon, 24 Jan 2011 17:48:14 +0200 > From: Igor R <boost.lists(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] [statechart] (custom) state queries for > asynchronous state machine > Message-ID: > <AANLkTim_eYbue02=dOA=0ouAi7wWDTaV9KWW0TXZ+Aum(a)mail.gmail.com<0ouAi7wWDTaV9KWW0TXZ%2BAum(a)mail.gmail.com> > > > Content-Type: text/plain; charset=UTF-8 > > > However, for the asynchronous case, access to the state machine is via a > > scheduler only - and I don't see how to get the information from there > nor > > is there any documentation on that in the tutorial. Any hints on how to > do > > this? > > With async. state machine such a direct access wouldn't be thread > safe. So the only way you can retrieve its state is by means of > events. I.e. you can enqueue an event, which contains some facility > for the response - like a ptr to a message queue or a slot for > boost.signals2 and so on. When processing this event, the machine > performs the query you want and returns you the answer through the > facility you provided. > Hi Igor, of course, that makes sense. I don't know why I didn't think of using a callback - but will try that now. Thanks for your prompt response, it's much appreciated! Loek

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Iostreams code_converter peculiarities
by Eddie Carle 25 Jan '11

25 Jan '11

I've been working on converting a the fastcgi++ library over to using boost::iostreams from std::iostreams and I've noticed some peculiarities that I can't seem to work passed. For one, how do you change the buffer size of the code_converter adaptor? The built in facilities don't seem to actually do anything. I am adding to a filtering_stream and have noticed that for the following statements... stream.push(code_converter<MyDevice>(myDevice), 8192); stream.push(code_converter<MyDevice>(myDevice, 8192)); stream.push(code_converter<MyDevice>(myDevice, 8192), 8192); All result in a buffer of 128 bytes. I can't figure out a way to actually change it. I've been monitoring what is going in the myDevice and it is always 128 byte chunks (or less). If I remove the code_converter from the stream and go directly in myDevice as per stream.push(myDevice, 8192); the buffer is sized as I want it to be and myDevice receives chunks of data maxing at 8192 bytes. Secondly, when using the statement stream.push(code_converter<MyDevice>(myDevice, 8192)); code_converter calls not MyDevice(const MyDevice&) for copying constructing the object but for some reason MyDevice(const MyDevice&, const long int&). What is that? Why is code_converter looking for such a constructor when I specify a buffer size for the code converter? Thirdly, I can not for the life of me make the code converter flush it's data. If I call a stream.strict_sync() should the code_converter not get flushed as well? It doesn't. Everything else in the chain does but the code_converter won't fully flush until destruction. Thanks. -- Eddie Carle

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Re: [Boost-users] reference access with boost::make_transform_iterator
by Patrick Sauer 25 Jan '11

25 Jan '11

Hi, I'm trying to use boost::make_transform_iterator to create an iterator for a custom class whose data is held in a map and where the iterator uses the vector of keys to access the values. In my problem, the values of the map are containers which hold large data. Since I can't afford to copy the data, I would like to access the data by reference via the iterator. However, when doing this, the data is corrupted, as is exemplified by the output of the simple example I have attached. As far as I can tell the problem lies in the use of the from_key functor, which is initialised using a reference to the map and is corrupted when passed through make_transform_iterator. Any ideas how I could do this properly using boost? Thanks, Patrick #include <iostream> #include <string> #include <vector> #include <boost/unordered_map.hpp> #include <boost/iterator/transform_ iterator.hpp> #include <boost/assign.hpp> #include <boost/assign/std/vector.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <boost/ref.hpp> using namespace boost::assign; namespace bl = boost::lambda; class holder { public: holder() : v() {}; holder( const std::vector<double>& in ) : v(in) {}; std::vector<double>& vector() { return v; }; const std::vector<double>& vector() const { return v; }; private: std::vector<double> v; }; class from_key { public: typedef holder result_type; from_key( const boost::unordered_map<std::string, holder >& m ) : map_(m) {}; const holder& operator() ( const std::string& in ) const { return map_.at(in); }; private: const boost::unordered_map<std::string, holder >& map_; }; typedef boost::transform_iterator<from_key, std::vector<std::string>::iterator > iterator; int main() { std::vector<std::string> keys; keys += "1","2","3"; std::vector<double> vals; vals += 1.0, 2.0, 3.0; holder h(vals); boost::unordered_map<std::string, holder > m; insert( m ) ( "1", h ) ( "2", h ) ( "3", h ); iterator it = boost::make_transform_iterator( keys.begin(), from_key( m ) ); iterator end = boost::make_transform_iterator( keys.begin(), from_key( m ) ); const std::vector<double>& v = it->vector(); std::for_each( vals.begin(), vals.end(), std::cout << bl::_1 << " " ); std::cout << std::endl; std::for_each( v.begin(), v.end(), std::cout << bl::_1 << " " ); std::cout << std::endl; }

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[Interprocess]
by Daniel Neuberger 24 Jan '11

24 Jan '11

Hi Ion (and everyone else), I looked through the recent commits and it looks like support for XSI shared memory has been added (https:// svn.boost.org/trac/boost/changeset/67451). Does this mean XSI is ready to use now? Do you think these changes will make it into the upcoming 1.46 release? Alternatively, do you think applying the above changeset to Boost 1.43 be sufficient to be able to use XSI shared memory? Thanks again, - Daniel P.S. Sorry if anyone got another similar message to this from me; I sent one in response to another message but think the thread was already too old.

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Random: How to get a different seed?
by Zoltán Lengyel 24 Jan '11

24 Jan '11

Hello, I am trying to make a simple program that can generate random integers in range, using boost::uniform_int. http://www.boost.org/doc/libs/1_45_0/doc/html/boost_random/tutorial.html#bo… This tutorial tells: "We use mt19937<http://www.boost.org/doc/libs/1_45_0/doc/html/boost/mt19937.html>with the default seed as a source of randomness. The numbers produced will be the same every time the program is run. One common method to change this is to seed with the current time (std::time(0) defined in ctime)." I have trouble getting this common method compile and work. Here's a tiny program that works, with the same seed at every run (like what the tutorial does), I have commented out my desperate tries to make the seed change. #include "uniform_int.hpp" #include "boost/random/variate_generator.hpp" #include "boost/random/mersenne_twister.hpp" #include <time.h> #include <iostream> using namespace std; using namespace boost; mt19937 gen; // time_t gen = time(0); int roll_die() { uniform_int<> dist(1, 6); variate_generator<mt19937&, uniform_int<> > die(gen, dist); //boost::variate_generator<time_t, boost::uniform_int<> > die(gen, dist); return die(); } int main() { for (int i = 0; i < 5; i++) cout << roll_die() << endl; return 0; } So, I would be glad, if someone could fix this for me, to have a different seed (depending on system time) at each start. Thanks!

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[Preprocessor] Relative Addresses in BOOST_PP_FILENAME_1
by Hossein Haeri 24 Jan '11

24 Jan '11

Dear all, I am trying to use BOOST_PP_FILENAME_1 for a header file in my current directory. Unless I hardcode the full address, GCC 4.5.1 (MinGW32, WinXP, SP3) says it can't find the same file in which I am using BOOST_PP_FILENAME_1! Is there any way I can go for relative file names? I have already checked the following -- neither works for the same reasons: #define BOOST_PP_FILENAME_1 "./Header.hpp" //1 #define BOOST_PP_FILENAME_1 ".\Header.hpp" //2 #define BOOST_PP_FILENAME_1 "Header.hpp" //3 TIA, --Hossein

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