- Boost-users - lists.boost.org

metafunction question
by John Dlugosz 13 May '10

13 May '10

A co-worker mentioned an interesting issue. I thought some metaprogramming, or at least more advanced insight into STL, might apply here. Consider a class derived from an STL collection. It features a special find(x) function that works with his search criteria. It returns an iterator into the collection. There are two forms needed: iterator find(x); const_iterator find(x) const; and the annoying part is that they contain exactly the same code. The implementation uses the inherited iterators and collection features to do the finding. The larger question is, is there a better way to approach that? The immediate question is, my thought of using a template helper requires the return type to be determined based on the constness of the incoming parameter for the collection type. Is there a handy metafunction for that already in existance? --John -silly company footer automatically added, sorry. TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

6 11

Re: [Boost-users] How can I use random library in a class? Can any one with kindness help me?
by Pete Bartlett 13 May '10

13 May '10

>Can anyone tell me why? You need to initialize the base class, not the base class's members. So: class Usedchild:public Used{ public: Usedchild(Matrix inputmatrix, Vec inputvec):Used(inputmatrix,inputvec){}; }; should work. It may also be worth your while to look at a text on C++ syntax before diving too deep into the complicated parts of Boost.

1 0

How can I use random library in a class? Can any one with kindness help me?
by fmingu 13 May '10

13 May '10

How can I use random library in a class? Can any one with kindness help me? I am using boost(version boost_1_37_0) random library in Dev-C++ with gcc. and the code is: #include "boost/random/normal_distribution.hpp" #include <boost/random.hpp> ................................. class TransferedSignal{ public: TransferedSignal(){ one(0.0,1.0) ; die(rng, one); }; double output(){ return die(); }; private: boost::mt19937 rng; boost::uniform_real<> one; boost::variate_generator<boost::mt19937&, boost::uniform_real<> > die; }; int main(int argc, char *argv[]) { TransferedSignal transferedsignal(); for (int i=0; i<100;i++) transferedsignal.output(); system("PAUSE"); return 0; } But the complier told me that: mainprojectme13.cpp: In constructor 'TransferedSignal::TransferedSignal()': mainprojectme13.cpp:154: error: no matching function for call to 'boost::variate_generator<boost::mt19937&, boost::uniform_real<double> >::variate_generator()' F:/CB2009/boost_1_37_0/boost/random/variate_generator.hpp:97: note: candidates are: boost::variate_generator<Engine, Distribution>::variate_generator(Engine, Distribution) [with Engine = boost::mt19937&, Distribution = boost::uniform_real<double>] F:/CB2009/boost_1_37_0/boost/random/variate_generator.hpp:87: note: boost::variate_generator<boost::mt19937&, boost::uniform_real<double> >::variate_generator(const boost::variate_generator<boost::mt19937&, boost::uniform_real<double> >&) mainprojectme13.cpp:155: error: no match for call to '(boost::uniform_real<double>) (double, double)' mainprojectme13.cpp:156: error: no match for call to '(boost::variate_generator<boost::mt19937&, boost::uniform_real<double> >) (boost::mt19937&, boost::uniform_real<double>&)' F:/CB2009/boost_1_37_0/boost/random/variate_generator.hpp:100: note: candidates are: typename Distribution::result_type boost::variate_generator<Engine, Distribution>::operator()() [with Engine = boost::mt19937&, Distribution = boost::uniform_real<double>] mainprojectme13.cpp: In function 'int main(int, char**)': mainprojectme13.cpp:173: error: request for member 'output' in 'transferedsignal', which is of non-class type 'TransferedSignal()' And I do not know how to solve it. Shauld I define "boost::variate_generator<Engine, Distribution>::variate_generator() " in the random library? But God knows what will be happened after that. Can any one with kindness help me? Thanks a lot.

2 2

[Range] Documentation problem in 1.43.0
by dariomt＠gmail.com 13 May '10

13 May '10

Hi, Some pages in the Boost.Range docs have a problem. E.g. the link http://www.boost.org/doc/libs/1_43_0/libs/range/doc/html/range/reference/al… shows this error message: Error extracting file: No matching files were found. Regards

1 0

[thread] Compiling libraries compatible with Boost.Thread using g++ on Linux
by Jorge Moraleda 12 May '10

12 May '10

Dear Boost.Thread experts, I wrote some libraries that are not multithreaded, but are supposed to be reentrant. I am compiling them from source. When I produce an executable that links these static libraries and invokes functions from these libraries from multiple threads via Boost.Threads, valgrind drd reports some race conditions in what appears to be straight forward memory access allocated with calloc. To be clear: the library function allocates some memory with calloc and later releases it. This memory is local to the function. I am wondering if I need to use any especial compiler flags when compiling the static libraries to make sure they are reentrant and compatible with Boost.Thread. In particular should I use or not use "-pthread" when compiling the libraries? Should I use "-pthread" when compiling and linking the final executable? I use gcc version 4.4.4 (Debian 4.4.4-1) and boost 1.42 (compiled from source because I am using Boost.Log). Thank you. Jorge Moraleda

1 0

[interprocess][boost 1.42.0] message_queue: mac OSX rosetta cfm app ==> macho dylib ==> macho app
by Jeff Flinn 12 May '10

12 May '10

I'm not able to see a shared message_queue which is created in an OSX mach-o bundled dylib(created with XCode 3.1.2), called from a CFM based app running under Rosetta(created with CodeWarrior 9.x) with a mach-o based app(created with XCode 3.1.2) waiting to receive message(s). I can send messages until the message count maxes out, but am blocked on the receive end. Has anyone else been (un)lucky enough to deal with this situation? I've been searching for info on just how Rosetta works and what it's implications are, without luck. Thanks, Jeff

1 0

Termination of breadth first search
by Eric Fowler 12 May '10

12 May '10

I noticed the Boost doc for dijkstra_shortest_paths() <http://www.boost.org/doc/libs/1_43_0/boost/graph/dijkstra_shortest_paths.hpp> says that the algorithm terminates when the priority queue is empty, which implies visiting every vertex, which is not necessary to find the shortest path between two vertices. I would like to use the algorithm to find the shortest path to a known vertex, which means stopping it before the queue is empty. At what point can I (the library client) decide to end a BFS search? Eric

2 1

[uuid] to string problem
by Saygin Arkan 12 May '10

12 May '10

Hi, I'm a newbie on boost. I've downloaded and used some features. I couldn't find how to cast uuid into string. #include "boost/date_time/gregorian/gregorian.hpp" #include <boost/uuid/uuid.hpp> #include <boost/uuid/uuid_generators.hpp> #include <boost/uuid/random_generator.hpp> #include <boost/uuid/string_generator.hpp> ... date GeneratorUtils::getRandomDate() { int year, month ,day; day = rand() % 30; month = rand() % 12; year = 1980 + rand() % 25; string str_date = "" + day + month + year ; date d(from_simple_string(str_date)); return d; string GeneratorUtils::getRandomID(){ random_generator gen; uuid u = gen(); return u.uuid_to_string(); // ERROR } It does not accept any to_string() function. Is there a way to convert from uuid to string in C++? (by the way, I can use the other things such as date d, uuid u etc.) -- H. Saygin Arkan Tampere University of Tech. CS / III - +358466646156

6 18

boost::thread - many compiler warnings
by Manfred Schwind 12 May '10

12 May '10

Hi, we are using boost to develp cross-platform stuff. I am the Mac developer. The Mac is a 64 bit Intel machine, development environment is Xcode, of course, using gcc as compiler. To create code as robust as possible I always turn on as many warning levels as possible. Usually I am using this: -Wall -Wextra -Wconversion -Wshorten-64-to-32 This worked great with all basic boost stuff that we've used previously. Now I tried just to include thread.hpp and I get many many compiler warnings! I just do: #include "boost/thread.hpp" The warnings are just two kinds of warnings: 1.) warning: implicit conversion shortens 64-bit value into a 32-bit value 2.) warning: missing initializer for member '...' An example for the first warning can be found in gregorian_calender.ipp (just showing relevant parts): template<typename ymd_type_, typename date_int_type_> BOOST_DATE_TIME_INLINE int gregorian_calendar_base<ymd_type_,date_int_type_>::week_number(const ymd_type& ymd) { ... unsigned long week = (juliantoday + day - julianbegin + 4)/7; if ((week >= 1) && (week <= 52)) { return week; } ... Here's clearly missing a cast to tell the compiler that it's ok to return the unisigned long as int. On most 64 bit systems, long is 64 bit but int is 32 bit. The second warning is caused by the following line in conversion.hpp: std::tm datetm = {}; // zero initialization is needed for extension members, like tm_zone In this line I get the "missing initializer" warning for every member of the struct, e.g. tm::tm_sec, tm::tm_min, tm::tm_hour etc. What's the intension by initializing with empty braces? IMO this is not a standard initialization method. Is there any chance that these errors get fixed? Any ideas how to use thread.hpp without reducing my warning levels? Does anyone have the same problems? Regards, Manfred Schwind -- http://mani.de - friendly software iVolume - listen to music hands-free LittleSecrets - the encrypted notepad Sahara - sand in your pocket Watchdog - baffle the curious

6 5

[GIL] does gil::variant<mpl::vector3<A, B, C> > constructor accept instances of gil::variant<mpl::vector2<A, B> > ?
by Nicolas Lelong 12 May '10

12 May '10

Hi ! the question is in the subject, but I can elaborate a bit. I have the set of all views supported by my application, defined as : typedef mpl::vector9< gray8_view_t , rgb8_view_t, bgr8_view_t, rgba8_view_t, bgra8_view_t , rgb32f_view_t, bgr32f_view_t, rgba32f_view_t, bgra32f_view_t > gil_all_views_t; typedef any_image_view<gil_all_views_t> any_view; Then I have a function, reading a file and returning an any_image_view, of a different type : typedef boost::mpl::vector3<boost::gil::gray8_view_t, boost::gil::bgr8_view_t, boost::gil::bgra8_view_t> tga_views_t; typedef boost::gil::any_image_view<tga_views_t> any_tga_view; The ' tga_views_t' is a subset of 'gil_all_views_t'. It seems that I cannot construct an 'any_view' instance, from an 'any_tga_view' ; I receive a bad_cast exception. Is there an existing function or construct I could use for this ? If I'm not mistaken, boost::variant (not the gil one) allow such constructs : it extracts the type of the value contained in the 'foreign' variant, and assigns this value to the new variant. Anyone could tell me what is the rationale behind having a special variant for boost::gil ? performance ? Wouldn't it be easier to replace it by boost::variant ? Thanks is advance, cheers, Nicolas.

4 5