November 2007 - Boost-users - lists.preview.boost.org

[boost-users] [program options]
by chun ping wang 02 Nov '07

02 Nov '07

HI how would I use program options to accept multiple input. Example I have a diffieHellmanKeyExchange program running through command prompt. // begin main program #include <iostream> #include <boost/tuple/tuple_io.hpp> #include <boost/program_options.hpp> #include "cppdef/BitOperation.cpp" #include "cppdef/mathfunc.cpp" #include "cppdef/IsPrime.cpp" #include "cppdef/DiffieHellman.cpp" #include <BigInteger.hpp> #include <BigIntegerUtils.hpp> int main( int ac, char* av[] ) { namespace po = boost::program_options; po::options_description desc("Allowed options"); boost::tuple<BigInteger, BigInteger> key_pair; desc.add_options() ("generate", "generates a pair of key") ("secert", po::value(&key_pair), "creates the share secret key"); po::variables_map vm; po::store(po::parse_command_line(ac, av, desc), vm); po::notify(vm); if (vm.count("generate")) { BigInteger my_prime = encryptcpw::random_prime<BigInteger>(&algocpw::Miller_Rabin<BigInteger>, 10); std::cout << "my prime: " << my_prime << "\n"; boost::tuple<BigInteger, BigInteger> pare(encryptcpw::dh_init<BigInteger>( my_prime )); std::cout << "pair of generated number: " << pare << "\n"; } if (vm.count("secert")) { const BigInteger p( encryptcpw::random_prime<BigInteger>(&algocpw::Miller_Rabin<BigInteger>, 10)); std::cout << encryptcpw::dh_secret<BigInteger>( p, boost::tuples::get<0>(key_pair), boost::tuples::get<1>(key_pair)); } } // end program The thing compiles but when I do DiffieHellman.exe --secert 817 697 I get this error. C:\CPW\cs_classes>DiffieHellmanEncrypt --secert 817 697 terminate called after throwing an instance of 'boost::program_options::invalid_ option_value' what(): in option 'secert': invalid option value '817' This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information.

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custom formatting the current local date time into a string
by Jeff 02 Nov '07

02 Nov '07

Hello, How can I grab the current local date and time, and format it so that it looks like this: YYYY_MMM_DD_HH_MM_SS ? I can't seem to get the facet stuff to work right. Thanks, Jeff

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[boost-users] [general question] deciding to use member function or not.
by chun ping wang 02 Nov '07

02 Nov '07

Hi is their a simple way *at compile time *to determine if a member function exist for a particular instance, if yes than use that function otherwise do not use it. example std::list<int> li; // check if unique is a member function of li, if yes use unique. li.unique(); // else use stl unique. std::unique(li.begin(), li.end());

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boost::posix::time_duration
by Michael Thurston 02 Nov '07

02 Nov '07

[boost][date_time] Hi there, I have a question about the boost::posix::time_duration class. It has accessors such as: - hours() - minutes() that return a data type of long. I would have expected it to return a datatype of boost::int64_t (or boost::int32_t) because could there be a risk that the return value would cause an overflow on an 8 bit embedded platform. Regards, Michael

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C++ & Enterprise Solutions
by Stefan Kok 02 Nov '07

02 Nov '07

Dear List If this is not the correct list to post to. Then please forgive my ignorance. I have been admiring the work of Boost and its contributors for some time now. My questions / comments : 1) Would their be any benefit to the community, developing a specification for C++ similar to SUN's J2EE and JEE specification ? I do realize this would require a mammoth effort as well as commitment in terms of resources. 2) Is it possible to establish such a project under the open source banner ? Given the commitment and resources required. 3) Would this be reinventing the wheel ? I know SUN & Java got there first (the J2EE thing). But C++ does have some very powerful features which makes it unique in some ways, templates for one. Thank you in advance. Stefan.

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[Boot.Pool] Opinions about inconsistent pointer types
by David Baird 01 Nov '07

01 Nov '07

Hi, I was looking through the Pool code and noticed that it presents inconsistent pointer types to the user ("void *" versus "char *"). For example, if the user wants to implement his/her own user allocator, they have to write it like, e.g. (using "char *" as the pointer type): struct default_user_allocator_new_delete { typedef std::size_t size_type; typedef std::ptrdiff_t difference_type; static char * malloc(const size_type bytes) { return new (std::nothrow) char[bytes]; } static void free(char * const block) { delete [] block; } }; However, other classes return "void *" as their pointer types, e.g. singleton_pool: template <typename Tag, unsigned RequestedSize, typename UserAllocator, typename Mutex, unsigned NextSize> struct singleton_pool { static void * malloc() { pool_type & p = singleton::instance(); details::pool::guard<Mutex> g(p); return p.p.malloc(); } } Is it really important that the types be different? I just think it might be more elegant to use "void *" in more places - it would make more things the same and be similar to e.g. "std::malloc/free". -David

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