July 2006 - Boost-users - lists.preview.boost.org

boost 64bit support on windows x64 on amd64 hardware
by Chu-Ming Ng 03 Jul '06

03 Jul '06

Hi, I am porting some code that uses boost from 32-bit to the 64-bit platform and would like to know if the boost library supports this platforms. thanks! Chu-Ming

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Retrieve multindex value type?
by Francesco Biscani 02 Jul '06

02 Jul '06

Hello, is there a way to retrieve from a multiIndex container the type of its content? I need to do something like this: template <class T> class my_class { private: T set; public: void insert(const T::value_type &); <------ ? }; Here T is a multiIndex container, and the insert function should add a term to the set. Hence "insert" must accept as input the kind of values that are stored in the multiIndex container. Is there a way to do so or should I just add another parameter to the template and use that as argument for insert? Thanks, Francesco

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Locking smart pointer
by Mattias Brändström 02 Jul '06

02 Jul '06

Hello! I have a small class to show you and perhaps get some comments on: <code> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> template <typename T> class LockPointer { public: class LockProxy { public: LockProxy(boost::shared_ptr<T> p, boost::shared_ptr<boost::recursive_mutex> mutex) : p_(p), lock_(new boost::recursive_mutex::scoped_lock(*mutex)) { } boost::shared_ptr<T> operator->() { return p_; } private: boost::shared_ptr<T> p_; boost::shared_ptr<boost::recursive_mutex::scoped_lock> lock_; }; LockPointer(boost::shared_ptr<T> o) : p_(o), mutex_(new boost::recursive_mutex()) { } LockProxy operator->() { return LockProxy(p_, mutex_); } private: boost::shared_ptr<T> p_; boost::shared_ptr<boost::recursive_mutex> mutex_; }; </code> The purpose of this class is to lock a mutex before each method call on an object of class T, and unlock the mutex when that call returns. It seems that this would be something that one would like to have in some cases. Maybe so many cases that it might be part of boost somewhere? I haven't found any library in boost that does this. Is there one? I haven't done anything like this before so it would be nice if anyone here could make some comments on the code. Will it do what I think it does or will it blow up in my face? :-) Regards, Mattias

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[serialization] Out of memory with Borland C++ Builder 60
by Federico Feller 02 Jul '06

02 Jul '06

Hi everyone. Im having problems compiling some code with Borland C++ Builder 6 that includes libboost serialization. In particular Im having troubles registrating a new class in order to be serialized. The new class, say A3, is a subclass of antother that is declared abstract, say A. A has already some subclases (A1, A2) that are serialized correctly. As I did for other subclasses on the same hierarchy, I added the instruction ar.register_type(static_cast<A3 *>(NULL)); in the load/save method of another class that serializes a pointer to the base class of the hierarchy. After doing that, I tried to compile the code and got the following error from the compiler: [C++ Fatal Error] if.hpp(72): F1008 Out of memory I really have no idea whats going on. Any ideas? Thanks Federico __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Re: [Boost-users] Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

This has the desired effects BUT ... I am not a software engineer .. so I would like to know is it would the proffessionals would consider ugly code ? #include<string> #include<boost/variant.hpp> typedef boost::variant< bool,std::string> BoostVariant; struct MyVariant:public BoostVariant { template<typename type> MyVariant(const type &theType):BoostVariant(theType){} MyVariant(const char *theCString):BoostVariant(std::string(theCString)){} }; int main () { MyVariant v("A String"); std::string &Sref(boost::get<std::string&>(v)); // NOw this does NOT throw bool &Bref(boost::get<bool&>(v)); // but this does return 0; }

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Re: [Boost-users] Boost.Variant: Is a char * really a bool ?
by Nindi Singh 01 Jul '06

01 Jul '06

Hi Yuval sorry .. i will ensure I put a RE: on my furtue replies ... but i have posted a reply with subject 'Boost.Variant: char[], a bool or std::string ? ' N

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Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

I sort of guessed that this implicit conversion was taking place ... but unfortunatley it wil make my variant very error prone .. and on the other hand I do want the capability to construct from a C string appropriatley. I think one possible soultion would be to derive from boost::variant<bool,std::string> and put in an explicit constructor for const char *, this will also let me get around other similar problems. However deriving from boost::variant .... ??? not sure how healthy that is. >To answer the question in the subject line: char* isn't bool, but it's >implicitly convertible to bool, which is probably (haven't really >checked, just an educated guess) what's causing you trouble. > >Nindi wrote: >> When I have a Boost.Variant templated on a bool and a std::string, I get >> the following behaviour .. >> >> #include<string> >> >> #include<boost/variant.hpp> .> >> typedef boost::variant< bool,std::string> BoostVariant; >> >> int main () { >> >> BoostVariant v("A String"); >> >> bool &Bref(boost::get<bool&>(v)); // this is ok >> >> std::string &Sref(boost::get<std::string&>(v)); // But this throws >> >> return 0; >> >> } > >Instead of > BoostVariant v("A String"); >try > BoostVariant v(std::string("A String")); > >I think it will solve your problems.

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Boost.Variant: Is a char * really a bool ?
by Nindi 01 Jul '06

01 Jul '06

When I have a Boost.Variant templated on a bool and a std::string, I get the following behaviour .. #include<string> #include<boost/variant.hpp> typedef boost::variant< bool,std::string> BoostVariant; int main () { BoostVariant v("A String"); bool &Bref(boost::get<bool&>(v)); // this is ok std::string &Sref(boost::get<std::string&>(v)); // But this throws return 0; }

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Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

... .. but this works fine .. #include<string> #include<boost/variant.hpp> typedef boost::variant<std::string> BoostVariant; int main () { BoostVariant v("A String"); std::string &Sref(boost::get<std::string&>(v)); // NOW this does NOT throw return 0; }

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Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

If I instantiate a Boost.Variant templated on a bool and a std::string , then I get the following behaviour ... not sure why #include <string> #include <Boost/Variant.hpp> typedef boost::variant< bool,std::string> BoostVariant; int main () { BoostVariant v("A String"); bool &Bref ( boost::get<bool &>(v)) ; // this is ok std::string &Sref ( boost::get<std::string> &(v) ) ; // but this throws return 0; } Is this what is supposed to happen ? Ninds

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