November 2008 - Boost - lists.boost.org

Support for std::nested_exception in Boost.Exception?
by Chris Newbold 26 Nov '08

26 Nov '08

Are there any plans (or any desire) for supporting the nested exception functionality (N2559) now in the C++0x draft in the Boost.Exception library? -Chris

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Using boost::filesystem with TCHAR
by Rob Caldecott 25 Nov '08

25 Nov '08

I wish to use the boost::filesystem library with some Windows apps and want to define TCHAR-friendly types. I *think* the following code should do the trick, giving me a boost::filesystem::tpath type, but is there anything I've missed? tpath.hpp #include <boost/filesystem.hpp> namespace boost { namespace filesystem { struct tpath_traits; typedef basic_path<std::basic_string<TCHAR>, tpath_traits> tpath; struct tpath_traits { typedef std::basic_string<TCHAR> internal_string_type; typedef std::basic_string<TCHAR> external_string_type; static external_string_type to_external( const tpath &, const internal_string_type & src ) { return src; } static internal_string_type to_internal( const external_string_type & src ) { return src; } }; } // filesystem } // boost

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Building 'stage' by default
by Vladimir Prus 25 Nov '08

25 Nov '08

We presently have 3 ways of building C++ Boost from top-level directory: - with 'stage' target -- only libraries are installed - with 'install' target -- both libraries and headers are installed - with no explicit target -- everything is built, but nothing installed It seems to me that the first two options are what the majority of users will want, so some of them should be the default. I have a local patch that makes 'stage' the default, and additionally prints the following message: Performing 'stage' build by default: - binaries installed into 'stage/lib' - headers not installed, use the source tree Use the 'install' target for complete installation. This message is printed only if no explicit target is specified -- if user types 'stage' or 'install', it's assumed he knows what he's doing. Anybody has any comments on this change in defaults, or about the wording of the message? Thanks, Volodya -- Vladimir Prus http://vladimir_prus.blogspot.com Boost.Build V2: http://boost.org/boost-build2

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Boost version meaning
by vicente.botet 25 Nov '08

25 Nov '08

Hi, I would like to know what is the meaning of the 3 numbers on the Boost version X.Y.Z. When X changes, i.e. when we could have a Boost version 2.0.0 Which number means a complete rewriten? Which number means an incompatible evolution? Which number means new functions? Which number means major bugs corrections? Which number means only minor bugs corrections? Is this written somewhere? If we were to version individual Boost libraries which will be the apropiated schema? Should all the libraries follow the same schema? What do you think of? X: complete rewriten or incompatible evolution Y: new functions or major bugs corrections Z: minor bugs corrections Thanks, Vicente

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Strange snippet around operator T()
by Joel Falcou 24 Nov '08

24 Nov '08

I was trying to find some decent way to declare named constants in my code and ended up with the following snippet : struct const_one { typedef int type; const_one() {} template<class T> const_one(T const& ) {} template<class T> operator type() const { static type const v = {1}; return v; } template<class T> operator T() const { static T const v = {1}; return v; } }; static const const_one one_; This allow me to have the following behavior : int k = one_; float e = one_; and have proper transtyping taking place when needed. Turning this into a macro allow to declare a large sample of named constant that auto-transtype them when needed. Now funny thing is that this structure allow me to do stuff like : float k = one_ / ( 1. + three_); Now if I remove the operator type(), I can't. But if i add a printf statement in this one, it is never called. Do someone has a clue about this behavior or am I playing with some undefined behavior ? TIA -- ___________________________________________ Joel Falcou - Assistant Professor PARALL Team - LRI - Universite Paris Sud XI Tel : (+33)1 69 15 66 35

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Re: [boost] dynamic_cast with WeakPtr?
by Sören Freudiger 24 Nov '08

24 Nov '08

ups, sorry, my fault.. the example seems to work, but I run into that problem because I tried to perform an dynamic_cast on that weak_ptr. How this should be done in this simple example? class Base { public: boost::weak_ptr<Base> neigh; }; class Derived : public Base { }; int main() { { boost::shared_ptr<Base> a(new Base); boost::shared_ptr<Derived> d(new Derived); a->neigh = d; d->neigh = a; //like that? boost::shared_ptr<Derived> pD2 = boost::shared_dynamic_cast< Derived >( a->neigh.lock()); } } -----Ursprüngliche Nachricht----- Von: Sören Freudiger [mailto:muffmolch@gmx.de] Gesendet: Montag, 24. November 2008 21:03 An: boost(a)lists.boost.org Betreff: dynamic_cast with WeakPtr? Hi @all Maybe you can help me. I tried to use weak_ptr for breaking circular references, but I found out that this pointers can't handle derived classes. But in my classes I have some neighbor relations that I want to tore with shared_ptr: class Base { public: boost::shared_ptr<Base> neigh; }; class Derived : public Base { }; int main() { { boost::shared_ptr<Base> a(new Base); boost::shared_ptr<Derived> d(new Derived) a.neigh = d; d.neigh = a; } //both objects are in memory because of circular references, but weak pointer doesn't work, //becaus eit seems to be unable handling derived classes... and there's no dynamic cast } How do you solve problems like that with boost pointers avoiding circular references? Best reagrds, SirAnn

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dynamic_cast with WeakPtr?
by Sören Freudiger 24 Nov '08

24 Nov '08

Hi @all Maybe you can help me. I tried to use weak_ptr for breaking circular references, but I found out that this pointers can't handle derived classes. But in my classes I have some neighbor relations that I want to tore with shared_ptr: class Base { public: boost::shared_ptr<Base> neigh; }; class Derived : public Base { }; int main() { { boost::shared_ptr<Base> a(new Base); boost::shared_ptr<Derived> d(new Derived) a.neigh = d; d.neigh = a; } //both objects are in memory because of circular references, but weak pointer doesn't work, //becaus eit seems to be unable handling derived classes... and there's no dynamic cast } How do you solve problems like that with boost pointers avoiding circular references? Best reagrds, SirAnn

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[threadpool] draft n2276 - interrupting tasks
by k-oli＠gmx.de 24 Nov '08

24 Nov '08

Hello, the draft specifies that the threapool::submit() function returns a future object in order to retrieve the result of the submited task. What about task cancelation/interruption? Instead returning a future the pool could return a task< R > object which contains a future< R > (access over R task< R >::get()) and interruption routines. boost.threadpool in the boost vault implements somthing like: task< R > threadpool::submit(...); template< typename R > class task { ... // interrupt task and return immediatly void interrupt(); // interrupt task and wait till it's finished void interrupt_and_wait(); // interrupt task and wait a certain time till it's finished or timeout template< typename TimeDuration > void interrupt_and_wait( TimeDuration const& td); // interrupt task and wait to a specific system time till it's finished or timeout void interrupt_and_wait( system_time const& st); bool interrupt_requested(); R get() { return impl_fut_->get(); } bool ready() const { return impl_fut_->ready(); } bool has_value() const; bool has_exception() const; }; Following Herb Sutters sugestions the submited task must be cooperative (contain interruption_point). What do you think? Should/Could it be added to the draft? regards, Oliver { return impl_fut_->has_exception(); }

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[Chrono] Proposed library now feature complete
by Beman Dawes 24 Nov '08

24 Nov '08

The Chrono library in the sandbox is now more-or-less feature complete. In addition to the C++0x features, timers have been added to replace the old Boost.Timer library which will become deprecated. The feature list includes: * The C++0x Standard Library's time utilities, including: o Class template duration o Class template time_point o Clocks: + |system_clock| + |monotonic_clock| + |high_resolution_clock| * Class template |timer|, with typedefs: o |system_timer| o |monotonic_timer| o |high_resolution_timer| * Process clocks and timers: o |process_clock|, capturing real, user-CPU, and system-CPU times. o |process_timer|, capturing elapsed real, user-CPU, and system-CPU times. o |run_timer|, convenient reporting of |process_timer| results. * The C++0x Standard Library's compile-time rational arithmetic. See http://svn.boost.org/svn/boost/sandbox/chrono The implementation is now working and lightly tested on Windows with VC++ 9.0 SP1 and Intel ia32 11.0 compilers, and on Ubuntu Linux with GCC 4.2.4 compiler. There is a bit more documentation, but it is still needs much work. Comments are welcome. --Beman

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Re: [boost] [MPL] new run-time algorithm: for all
by thijs＠sitmo.com 23 Nov '08

23 Nov '08

---- Oorspronkelijk bericht ---- Van: Larry Evans <cppljevans(a)suddenlink.net> Verzonden: 23 Nov 2008 18:33 +00:00 Aan: <boost(a)lists.boost.org> Onderwerp: Re: [boost][MPL] new run-time algorithm: for_all On 11/23/08 11:43, George van Venrooij wrote: > Larry Evans wrote: > >> Judging from the "what is it?" on that tinyurl, it is the cross product >> of the mplbook's exercise 7-8 mentioned in my previous post. > > It indeed has similar behavior when feeding it 2 sequences as the cross > product, or to be more precise, an outer product (as you mentioned > earlier) since both sequences need not have the same length. > > Looking at Wikipedia's definition: > http://en.wikipedia.org/wiki/Outer_product then my algorithm produces > the outer product when called with 2 sequences. When called with 3 > sequences, it generates some kind of 3-way outer product that I am not > able to find a good name or definition for. Perhaps Tensor product? _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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