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big int library
by Vaclav Vesely 16 Apr '03

16 Apr '03

Are there any plans about adding a big int library to the Boost? There are at least two implementations in the Sandbox. Thanks, w

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command line parsing
by cl_corba_at 16 Apr '03

16 Apr '03

What is the "boost way" of parsing command line arguments? When I searched the archives, some user recommended spirit for this task, but this seems to heavy-weighted for me. I tried tokenizer, but a seperator for the command line is not provided. - you have to remove quotations marks (only escaped_list_separator can do this) - your have to ignore multiple tokens (only char_seperator can do this) If I write this seperator its still wouldn't provide the api I would like to see for a command line parser. I saw in the past there have been an attemp by Bill Kempf to provide a command line parser for boost but it didn't find its way into the library from reasons I don't know. So is there a recommended way to parse options I did overlook? Is a command line parser planned? Thanks for your answers, CL

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GNU istream::scan
by Pat McCormack 15 Apr '03

15 Apr '03

Hi Is there anything like the GNU extension istream::scan() (to use a scanf style format string) in the Boost libraries? The boost format library seems designed to work solely on output streams (am I right on this?) Thanks Pat

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RE: [Boost-Users] Boost weak_ptr<>
by bjorn.karlsson＠readsoft.com 15 Apr '03

15 Apr '03

> From: Edward Diener [mailto:eddielee@tropicsoft.com] > > I don't understand what the practical use of Boost weak_ptr<> > is ? Anyone > like to clue me in ? I understand that Boost weak_ptr<> > creates an internal > reference to a Boost shared_ptr<> but I don't understand what that is > supposed to accomplish. A weak_ptr is an observer of the pointee, i.e it doesn't take part of the lifetime management of the resource. One use for it is to break cyclic dependencies; another is to avoid dangling pointers. When a shared_ptr deallocates its pointee, it notifies the weak_ptrs. When the weak_ptr is subsequently used, it knows that the resource is gone (compare this with storing raw pointers, where there is no way to tell whether the pointer is still valid or not). Example: A Company class has a container that holds elements of type shared_ptr<Employee>. Now, the Supervisor class needs to know things about certain Employees, but it cannot/must not control their lifetime (in the context of the Company class, that is). Rather than asking the Company to search through each Employee (for example by name) each time Supervisor needs to access/update some Employee information, it caches information in weak_ptr<Employee> for efficient access. If an Employee quits (is removed from the container of shared_ptr<Employee>), the Supervisor class will be informed of this the next time it tries to access that weak_ptr<Employee>. At the time of access, a (temporary) shared_ptr is created from a weak_ptr, to ensure that the pointee isn't deleted in the midst of using it. Without weak_ptr, the above would be hard(er) to accomplish: * Asking Company to find an Employee each time it is needed may be too inefficient. * Storing shared_ptr<Employee> in the Supervisor class interferes with lifetime management and can cause inconsistent state. * Storing a raw pointer to an Employee is extremely dangerous (known as the dangling Employee problem); there's no way of telling if the pointer is valid. Bjorn Karlsson

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shard_ptr
by Christian Gmeiner 15 Apr '03

15 Apr '03

Hi! I want to use boost's shared_ptr in my project, which is a dll. At the moment it looks like this: in the h: extern MY_API CCPUDetect * gCPU; in the cpp: CCPUDetect * gCPU = CCPUDetect::GetInstance(); I have problems to make the same with boost, so that gCPU is a smartpointer. Thanks, Christian Gmeiner [Non-text portions of this message have been removed]

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Boost weak_ptr<>
by Edward Diener 15 Apr '03

15 Apr '03

I don't understand what the practical use of Boost weak_ptr<> is ? Anyone like to clue me in ? I understand that Boost weak_ptr<> creates an internal reference to a Boost shared_ptr<> but I don't understand what that is supposed to accomplish.

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boost::date_time don't work under Kylix
by Konstantin M. Litvinenko 15 Apr '03

15 Apr '03

Hello, All! #include <boost/date_time/posix_time/posix_time.hpp> #include <iostream> int main() { using namespace boost::posix_time; using namespace boost::gregorian; date d(1990,1,1); ptime t(d); std::cout << to_simple_string(t); return 0; } I have tested this sample under 4 compilers - vc7, gcc 2.96 asplinux, builder 5.6.4 and kylix3 (compiler borland 5.6). Under Kylix it produce floating point error. I figure out that this happens because t, after this line ptime t(date(1990,1,1)); have {0} (as i see in debuger). Is this library or kylix bug? It seems to be a __int64 arithmetic error but i am not sure. With best regards, Konstantin M. Litvinenko aka Dark Angel. E-mail: darkangel(a)malva.ua

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Question about SPirit parser terminology
by satya_vajja 14 Apr '03

14 Apr '03

Can anyone explain me what is the difference between a rule, grammar and parser in SPIRIT parser library. Thanks

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Macintosh Carbon Thread Error with Boost 1.30.0
by Bobby Thomale 14 Apr '03

14 Apr '03

Hey guys, I just tried to get the new Boost 1.30.0 release to work on MacOS, using TARGET_CARBON (with threads turned on). I have a problem to report: there's a new "lightweight mutex" being used by the smart pointer library. There does not seem to be a lightweight mutex implementation for the "Carbon MP tasks" thread implementation. So - when I compile my code under Boost 1.30 I end up at: # error Unrecognized threading platform in lightweight_mutex.hpp when it tries to compile any of the smart pointer stuff. Help! :-) -- Bobby --------------------------------------------------------------------- Bobby Thomale Senior Software Developer Inoveon Corporation http://www.inoveon.com/ ---------------------------------------------------------------------

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uBlas Lapack binds from Sandbox - pb with templ. specialisation
by geert_ceuppens 14 Apr '03

14 Apr '03

Toon & Kresimir, I've downloaded the lapack and blas binds from the boost sandbox, and I found out the hard way (again :^( ...) the 'features' of the VC6 compiler, i.e. the lack of support for template specialisation. The offending code is: (line nbr may differ due to versioning) *) boost\numeric\bindings\traits\algorithm.hpp(45): template < typename T > struct is_equal vs: template < typename T > struct is_equal< boost::numeric::ublas::matrix< T > > --> template class has already been defined as a non-template class *) libs\numeric\bindings\blas\test\blas.hpp(51): template < typename T > struct assign_multiplier vs: template < typename T > struct assign_multiplier< std::complex< T > > *) boost\numeric\bindings\traits\traits.hpp(46): template <typename V, typename T = typename V::value_type> struct default_vector_traits vs: template <typename V, typename T> struct default_vector_traits<V const, T> *) boost\numeric\bindings\traits\traits.hpp(112 & 114): This one gave more errors: template <typename MatrixT> inline typename matrix_traits<MatrixT>::pointer matrix_storage (MatrixT& m) { return matrix_traits<MatrixT>::storage (m); } error C2039: 'pointer' : is not a member of 'matrix_traits<M>' error C2146: syntax error : missing ';' before identifier 'matrix_storage' error C2433: 'pointer' : 'inline' not permitted on data declarations error C2501: 'pointer' : missing storage-class or type specifiers error C2059: syntax error : ';' error C2065: 'MatrixT' : undeclared identifier error C2065: 'm' : undeclared identifier 'matrix_storage' : missing storage-class or type specifiers syntax error : missing ';' before '<end Parse>' Any chance of providing non-specialised versions of these so I can use the VC6 compiler? Thanks - Geert

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