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non-member reset()
by Stefan Slapeta 28 Jan '05

28 Jan '05

Hi all, do we have a non-member reset() somewhere? Something like template <typename T> void reset(T& t) { std::swap(t, T()); } (of course to be refined...) Stefan

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Meta-math
by Jason Hise 28 Jan '05

28 Jan '05

I was just playing around, trying to compute a square root at compile time. I came up with the following: template < unsigned int N, unsigned int X = 1, unsigned int X2 = ( X + N / X ) / 2 > struct Sqrt { typedef typename Sqrt < N, X2 > :: ValueHolder ValueHolder; }; template < unsigned int N, unsigned int X > struct Sqrt < N, X, X > { struct ValueHolder { enum ValueStorage { Value = X }; }; }; This works for most values, but unfortunately some ( like 80 ) end up oscillating and X never becomes equal to X2. How could I go about correcting this? -Jason

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Re: [Osl-sysadmin] Re: devel ML archive stuck again
by David Abrahams 28 Jan '05

28 Jan '05

Jeff Squyres <jsquyres(a)osl.iu.edu> writes: > Dave -- > > As I have indicated before, I am not the OSL sysadmin. Please stop > telling people that I am. Sorry, I must have missed that announcement. > The OSL sysadmin is now DongInn Kim (not Larry). The > osl-sysadmin(a)osl.iu.edu address will continue to be your primary > contact address. Okay, everyone, please take note. -- Dave Abrahams Boost Consulting www.boost-consulting.com

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Re: Multiton
by Dave Handley 28 Jan '05

28 Jan '05

Jason Hise wrote: > > I agree entirely... which is why I plan to make multiton a sibling class > instead of making the singleton support it with additional policies. It > will live in the same namespace and possibly be able to utilize some of > the same policies that the singleton does (for instance any allocator > that doesn't restrict creation to one instance) Excellent... > Almost. The key passed in to GetInst would be templated, and Child > would be the multiton itself. However, upon further meditation I wonder > if having Child a separate type would be preferable. I guess the > question at hand is how important it is to enforce that there can only > be instances that correspond to a key. With your model, anyone could > easily instantiate a Child. > What I was essentially thinking about was a class that IS actually a singleton, then a class which you inherit off to generate the "multiton" using CRTP in a similar way to the singleton. Essentially your classes would be something like (with slightly better names than my last attempt of Child and multiton): template <class M> class multiton_factory_impl : public singleton<multiton_factory_impl<M> > {}; and class my_multiton : public multiton<my_multiton> {}; template <class M> class multiton { typedef typename multiton_factory_impl<M> multiton_factory public: static M* GetInst( int number ) { return multiton_factory::GetInst()->GetInst( number ); } // All the usual private constructors to force creation through here // along with appropriate friending to support it }; This is slightly better than my last suggestions because the GetInst function is actually in the real multiton, rather than in the singleton. Anyway, I look forward to seeing your implementation. Dave Handley

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Re: Problem Linking to Serialization Libs
by Jared McIntyre 28 Jan '05

28 Jan '05

> Are you including libboost-serialzation.lib (or ?) in your project? > > Robert Ramey Yes, specifically the version I built with multithreaded debug dll (otherwise there are a number of duplicate definition errors). I was trying to use the wide version of the xml archive earlier and was therefore linking to both libboost_serialization.lib and libboost_wserialization.lib, but was running into several more linking failures, so I went to the standard version in hopes of reducing some of the complexity. I forgot to mention in the previous email that these are the static library builds. Jared

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Problem Linking to Serialization Libs
by Jared McIntyre 28 Jan '05

28 Jan '05

I'm having difficult linking to the serailization libraries. Here is the basic setup: Visual Studio 7.1 Boost 1.32 Aerialization libraries built using runtime library : Multithreaded Debug DLL using xml_oarchive & xml_iarchive I'm getting the following linking errors: BusBuild.obj : error LNK2019: unresolved external symbol "public: void __thiscall boost::archive::xml_oarchive_impl<class boost::archive::xml_oarchive>::save(class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > const &)" (?save@?$xml_oarchive_impl@Vxml_oarchive@archive@boost@@@archive@boost@@QAEXABV?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@Z) referenced in function "public: static void __cdecl boost::archive::save_access::save_primitive<class boost::archive::xml_oarchive,class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > >(class boost::archive::xml_oarchive &,class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > const &)" (??$save_primitive@Vxml_oarchive@archive@boost@@V?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@save_access@archive@boost@@SAXAAVxml_oarchive@12@ABV?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@Z) BusBuild.obj : error LNK2019: unresolved external symbol "public: void __thiscall boost::archive::xml_iarchive_impl<class boost::archive::xml_iarchive>::load(class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > &)" (?load@?$xml_iarchive_impl@Vxml_iarchive@archive@boost@@@archive@boost@@QAEXAAV?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@Z) referenced in function "public: static void __cdecl boost::archive::load_access::load_primitive<class boost::archive::xml_iarchive,class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > >(class boost::archive::xml_iarchive &,class std::basic_string<unsigned short,struct std::char_traits<unsigned short>,class std::allocator<unsigned short> > &)" (??$load_primitive@Vxml_iarchive@archive@boost@@V?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@load_access@archive@boost@@SAXAAVxml_iarchive@12@AAV?$basic_string@GU?$char_traits@G@std@@V?$allocator@G@2@@std@@@Z) Any ideas of how to get around this?

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devel ML archive stuck again
by Gennadiy Rozental 28 Jan '05

28 Jan '05

Is there direct mal I could use to notify when it happends? Gennadiy

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serialization lib minor suggestion (to Robert Ramey)
by Sergey Skorniakov 28 Jan '05

28 Jan '05

Hello, Robert! I've got a couple of linker error with std::wostream & operator<<(std::wostream &os, const char t) and std::wostream & operator<<(std::wostream &os, const char *t) when defining custom archives and explicitly instantiating them in separate library. Can you declare these operators as inline - its would be more convenient for anyone performing same task? With best regards, Sergey.

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boost::mem_fn
by John Maddock 28 Jan '05

28 Jan '05

Am I right in thinking that boost::mem_fn: 1) Does not inherit from std::unary_function or std::binary_function when it should (as per the TR)? 2) Does not support volatile qualified member functions? Many thanks, John.

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Interfaces Library (structural subtyping)
by christopher diggins 28 Jan '05

28 Jan '05

Several people have told me the technique which I referred to as "retroactive polymorphism" is more correctly labelled "structual subtyping". Christopher Diggins Object Oriented Template Library (OOTL) http://www.ootl.org

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