March 2008 - Boost - lists.boost.org

Is the review schedule correct on the new website?
by dan marsden 04 Apr '08

04 Apr '08

Hi I'm the review manager for the Egg library that starts on 31 March. I used to see Egg in the review schedule, but I checked today and we'd disappeared. I've assumed that is some versioning issue with the website, and kicked off the review anyway, I hope thats ok with the review wizard(s). The online schedule doesn't contain any reviews scheduled after Feb of this year, so it just looks like an out of date copy to me. Cheers Dan ___________________________________________________________ Yahoo! For Good helps you make a difference http://uk.promotions.yahoo.com/forgood/

3 2

[Logging] Defining a to_string destination
by Manuel Jung 04 Apr '08

04 Apr '08

Hi, I would like to log to a standard container like std::list<std::string> or something similar, so i can send my logs to another program over network. But i have problems defining my own destination. For now it would be ok, to log just to a string. But i don't understand how to define my own destination in the right way. I looked at http://torjo.com/log2/doc/html/namespaceboost_1_1logging_1_1manipulator.htm… but i don't understand the "sharing data" part well. Maybe someone can help me out here? I have so far: struct to_string : boost::logging::destination::class_<to_string, boost::logging::destination::implement_op_equal::has_context> { std::string s; to_string(std::string s) : s(s) {} bool operator==(const to_string& other) { return s == other.s; } // param = const std::string& // (in other words, it's the arg_type from your destination base class) void operator()(param msg) const { // s.append(msg); } But even that is not compiling. Any help would be appreciated! :-) Greetings Manuel Jung

2 9

Giving names to formal parameters of lambda expressions: a named placeholder trick.
by Giovanni Piero Deretta 04 Apr '08

04 Apr '08

One thing that has always bothered me of the various boost lambda abstractions (be them compile time lambdas a-la mpl or runtime lambdas a-la Boost.Lambda, phoenix or plain bind) is that you must use non descriptive names for your argument paceholders. What I would like is to be able to declare the names of the formal parameters of my lambdas. Sure, in mpl you can have your placeholder names by typedef-ing the standard placeholders to a new name; with runtime lambdas, you can create custom objects with the same type of standard placeholders. In all those cases you still need to declare them outside of the lambda expression. While reading the Proto example "Vector: Adapting a New Terminal Type", I discovered something new about C++: you can forward declare class names inside a template parameter declaration. That is, something like this is actually possible: void foo () { int i = lambda // introduce formal parameter names [ _<class left>(), _<class right>() ] // now use them! [_<left>() + _<right>()] // actual parameters values ( 10, 20 ); } The _<...>() looks a bit clumsy, but it might be actually usable. I think that such a trick might really shine with the so called "round lambda"s; in the past I have toyed with a template class 'compose' that used the round lambda syntax for functional composition: Assume you have two polymorphic function objects types that work on ranges called 'fold' and 'reverse' (which do the obvious thing implied by their names): struct reverse_fold { template<typename Sig> struct result; template<class Range, class Init, class Op> struct result<reverse_fold(Range, Init, Op)> { private: typedef typename boost::result_of<reverse(Range)>::type reversed; public: typedef typename boost::resuld_of<fold(reversed, Init, Op)>::type type; }; template<class Range, class Init, class Op> typedef typename result<reverse_fold(Range, Init, Op)>::type operator()(Range const& range, Init i, Op op) const { return fold()(reverse()(range), i, op); } }; could be rewritten, using 'compose', as: typedef compose<fold(reverse(_1), _2, _3> reverse_fold; Which saves quite a bit of typing! (of course it works only with stateless function objects). Still the non-descriptive _N placeholders bother me. Using the named placeholder trick it would become: typedef compose< // introduce formal args names args< class range , class init , class op > // expression , fold(reverse(range), init, op) // function name > reverse_fold; With complex expressions, this could be quite a readability improvement. Except for confirming that the above expression does actually compile (at least with gcc), I have yet to try to implement it, but I think it should be fairly easy. Comments? -- gpd

5 32

CGI/FastCGI library preview
by Darren Garvey 03 Apr '08

03 Apr '08

Hi everyone, Some of you may remember the CGI library that was being worked on for last year's GSoC. It still needs *loads* of work before it could be considered ready for review, but I think it's moved on far enough since I last updated this list that some more feedback would be very useful. Pre-built docs are online: http://cgi.sf.net/doc Current source is at: *http://tinyurl.com/2bsbsf* (browser-friendly) *http://tinyurl.com/2xcye2* (check-out) ** This is alpha-grade source: functional and ugly ** The examples there have been tested on ubuntu with gcc 4.1.2 and gcc 4.2 and on windows with MSVC 9. The FastCGI examples will only work on linux for now. I've not managed to get it working with lighttpd as-is but it seems to work fine on Apache 2.2 with mod_fastcgi or mod_fcgid (and shows some healthy benchmarking results). Any and all comments/suggestions/criticisms are welcome. Kind regards, Darren

2 3

[thread] Interest in a locking pointer and lockable concept
by klaus triendl 03 Apr '08

03 Apr '08

Hi, is there any interest in something like a locking pointer and a type that I call "lockable" that pairs any type with a mutex? Inspired by Andrei Alexandrescu's article "volatile - Multithreaded Programmer's Best Friend" on ddj I implemented a concept similar to a locking pointer called "lock_acquirer" that collects acquisition of a mutex and a volatile cast of the locked type. It is even more threadsafe to use than a locking pointer. Additionally I made a class "lockable" that pairs a (volatile) type with a mutex type, wrapping both in a distinct type, which has first the advantage that the type to protect and the mutex are glued together, and second that it encapsulates volatile qualifier correctly. Also, the locked type in a lockable can, if wanted, by a restricted interface only be accessed by a lock_acquirer thus forcing the programmer to a very threadsafe programming style. I can post my implementation along with a simple example to the boost vault. Klaus

6 25

gsoc prposal
by Inosh Goonewardena 03 Apr '08

03 Apr '08

Hi, I have send a proposal to gsoc regarding the JSON Archives for Boost.serialization. I have attached my propsoal with this e mail

3 2

#pragma warning (dsiable : 4996) ineffective?
by Roland Schwarz 02 Apr '08

02 Apr '08

I have seen some attempts from library authors, e.g. boost/thread/win32/conditiona_variable.hpp to get rid of the annoying MSVC warnings. However this seems not to work (at least on my machine). There seems to be some unintended interdependence with _SCL_SECURE_NO_DEPRECATE. I was not able to find out what exactly is causing the warnings not go away. Hoever, compiling with _CRT_SECURE_NO_DEPRECATE and _SCL_SECURE_NO_DEPRECATE quiets the build. Couldn't this issue be handled by the boost config headers? Is this something wrong with my setup only, or do others experience the same problem? Thank you, to anyone who cares. -- _________________________________________ _ _ | Roland Schwarz |_)(_ | aka. speedsnail | \__) | mailto:roland.schwarz@chello.at ________| http://www.blackspace.at

6 7

type_with_alignment.hpp VC8 error
by Ralf W. Grosse-Kunstleve 02 Apr '08

02 Apr '08

Hi, svn revision 43952 broke my VC8 build: C:\AUTOBU~1\sources\boost\boost/python/converter/as_to_python_function.hpp(21) : error C2719: 'unnamed-parameter': formal parameter with __declspec(align('8') ) won't be aligned The compilation command is attached. Ralf cl /nologo /D_SECURE_SCL=0 /D_CRT_SECURE_NO_DEPRECATE /wd4996 /Zm800 /MD /GR /EH sc /DBOOST_DISABLE_THREADS /DNDEBUG /Ox -DBOOST_ALL_NO_LIB -DBOOST_PYTHON_MAX_ BASES=2 /IC:\AUTOBU~1\sources /IC:\AUTOBU~1\sources\boost /IC:\AUTOBU~1\build\ base\python\include /c C:\AUTOBU~1\sources\boost_adaptbx\optional_ext.cpp /Fob oost_adaptbx\optional_ext.obj

5 5

[gsoc 2008] A C++ Remote Method Invocation Framework using Boost.Asio
by salinda h 02 Apr '08

02 Apr '08

Hi All, For the google summer of code 2008, I wish to build a Cross Platform Remote Method Invocation Framework for C++ using Boost.Asio, similar to Java's remote method invocation (RMI). I will provide some macro definitions to create the proxy code. Please provide me your comments to adjust this idea to best suit the interests of boost community. I higly appreciate your suggestions. A sample code that will use this framework wold look like, account.h -------------- DECLARE_BEGIN_PROXY(account) DECLARE_METHOD_1(deposit, void, double); DECLARE_METHOD_0(get_balance, double); DECLARE_END; class account { .......... ......... } Server Code ----------------- account acc = new account("Foo", 250); Server s = new server(server::TCP, 19000); s.attach("Foo", acc); s.run(); Client Code ---------------- account_proxy acct = account_proxy::get_proxy("172.25.44.195", server::TCP, 19000, "Foo"); acct.deposit(100); double balance = acct.get_balance(); Thank You, Salinda

7 6

Two 1.35 Issues
by Jared McIntyre 01 Apr '08

01 Apr '08

Has something changed in the way you build libraries? I'm building using the following command: bjam --build-dir=builddir --toolset=msvc-8.0 stage This no longer builds any of the libboost* versions, nor any debug builds when run against 1.35. bjam version is 03.1.16. I'm not having any issues with gcc builds. Secondly, is there a link on the website to the 1.35 Getting Started docs? I ended up finding it through the searc on the site. It might be nice if that was linked to from the documentation section. Maybe even listed at the top. Thanks, Jared

10 12