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How to use boost::bind
by Darren Cook 26 Aug '03

26 Aug '03

Hi, I have a project with many occurences of while loops iterating through a container, and operating on the data. I'd like to use for_each() and turn them into one-liners, but I don't like writing one-off functor classes. I was hoping boost::bind could help, but I've read the docs, scratched my head, and failed to work out how the examples apply to my case. Maybe they don't and I'm trying to use it for something it cannot do? See an example below. My function currently looks something like grab_keys() and I want it to look like grab_keys2(). Could some kind soul show me how to write this? (or explain why it cannot be written). Thanks, Darren ------------------------- class Info{ public: int key; std::set<int> points; }; class InfoContainer{ public: Info* get(int); }; void grab_keys(const InfoContainer &cs,const Info *c){ std::set<int> list; std::set<int>::const_iterator i=c->points.begin(); while(i!=c->points.end()){ Info *ec=cs.get(*i++); list.add(ec->key); //Previous two lines could be written: list.add(cs.get(*i++)->key); } //Do something with list here. } void grab_keys2(const AllInfo &cs,const Info *c){ Points list; std::for_each(c->points.begin(),c->points.end(), boost::bind( /* what goes here? */ ) ); //Do something with list here. }

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newbie: comand line for g++
by Ruslan Talpa 26 Aug '03

26 Aug '03

how to staticaly link a boost library (regex) to a project (what is the g++ command line for that) Thanks PS i have only used VC till now.

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XML output from Boost test framework.
by Jarl Friis 26 Aug '03

26 Aug '03

Hi. The release notes on Boost test framework says: XML log format is introduced XML report format is introduced I would like to know how I use those features, the documentation says nothing about it, at least I can't find it. Thanks in advance. Jarl

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ClearCase and Boost
by Matt Trentini 26 Aug '03

26 Aug '03

Heya, The best way I've found to import Boost into ClearCase is by using "clearfsimport". If anyone wants a hand in setting up the parameters (it's a bit tricky - please make sure you don't use the mklabel and preview options together, otherwise you'll lock the VOB!) let me know. Cheers, Matt

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filesystem in CVS differs from 1.30.x ?
by Anders Moe 26 Aug '03

26 Aug '03

Hi all. I'm somewhat confused about how to use filesystem, since it appears that the CVS version differs from 1.30.x. In particular, the following simple snippet suddenly wouldn't compile on 1.30.2 using MSVC 7.1: boost::filesystem::path p("dd"); boost::filesystem::ofstream os("dd"); It works, however, with the current CVS version. In fact, I have failed to compile any variant of the above under 1.30.2. Regards, Anders Moe.

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mem mapping containers
by spam_me_da 25 Aug '03

25 Aug '03

I'd like to know if there is any available implementation of a memory mapped linear array. (Linux) Thanks -K

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boost::lambda how to question
by Eric Twietmeyer 25 Aug '03

25 Aug '03

Hello, I'm been having great fun getting to know and starting to use the lambda library over the past month or so. I can't believe how well the optimizing compiler I have (Vc7.1) is able to convert these lambda expressions used in for_each or find_if into tight loops. However, there I things I'm certain are possible, but I haven't been able to figure out. More examples of using the library than are found in the doc would be extremely useful. For instance, how do I do the equivalent of the following using a single for_each with suitable lambda expression as operator? using namespace boost::lambda; std::vector<int> vec1; std::vector<int> vec2; struct tOp { std::vector<int>& m_vec; tOp( std::vector<int>& vec ) : m_vec( vec ) {} void operator()( int entry ) { std::vector<int>::iterator it = std::find_if( m_vec.begin(), m_vec.end(), _1 == entry ); if ( it != m_vec.end() ) m_vec.erase( it ); } }; // How to use lambda expression here for third arg? std::for_each( vec1.begin(), vec1.end(), tOp( vec2 )); Basically, I have two lists (vectors) that overlap. I want to erase all elements from the one vector from the other vector, i.e. determine if the element from vec1 exists in vec2, and if so erase it from vec2. If this is possible and relatively straight forward using a lambda expression, I would love to see an example. Thanks in advance, Eric Twietmeyer PS It looks like something of this sort can be done with std::set_difference if one outputs into a third vector, but for argument's sake, let's assume I don't want to introduce a third vector. --------------------------------- Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software [Non-text portions of this message have been removed]

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boost.thread, DEC C++ (OpenVMS)
by Johan Nilsson 25 Aug '03

25 Aug '03

Hi, I've just tried to compile boost.thread under OpenVMS and got it working mostly fine, with a few quirks. I'm using Boost 1.30.2 and DEC C++ 6.5 under OpenVMS Alpha 7.1-1H1. OpenVMS provides a compliant(?) pthreads implementation. Note that I did _not_ use Boost.jam (I did try, but couldn't get it going). Compiling the .cpp files under BOOST_ROOT/libs/thread/src works pretty fine, once having defined BOOST_HAS_THREADS, BOOST_HAS_PTHREADS and BOOST_HASTIMEOFDAY on the compiler's commandline. But not for tss.cpp - I get the following error: ------------------------------------------------------------------------- res = pthread_key_create(&m_key, cleanup); .....................................^ %CXX-E-INCOMPATIBLEPRM, argument of type "void (*)(void *)" is incompatible with parameter of type "void (*)(void *) C" at line number 192 in file DISK$USER1:[COMMON.BOOST.LIBS.THREAD.SRC]TSS.CPP;1 ---------------------------------------------------------------------------- --- After some digging around I found out that the error only appears when using the compiler switch "/standard=strict_ansi", which is what I'm using all the time. Now to me it looks like the DEC C++ compiler believes that name mangling isn't the only thing that differs between "C" and "C++" linkage - does anyone here have any comments on that? See below for a small example (and possible way to work around this in the boost.thread implementation): ------ sample.cpp ------- extern "C" { typedef void (*c_linkage_cb_t)(void*); void c_linkage(void (*pfn)(void*)); } inline void cpp_linkage_using_c_typedef(c_linkage_cb_t pfn) { c_linkage(pfn); } inline void cpp_linkage(void (*pfn)(void*)) { c_linkage(pfn); } ---------------- end sample.cpp ------------------- And here's the output from the compiler: $ cxx /standard=strict_ansi t.cpp c_linkage(pfn); ..................^ %CXX-E-INCOMPATIBLEPRM, argument of type "void (*)(void *)" is incompatible with parameter of type "void (*)(void *) C" at line number 19 in file DISK$USER1:[COMMON.BOOST.LIBS.THREAD.SRC]T.CPP;11 I don't know if this is a compiler bug or not, but in order to work around this in boost.thread, wouldn't it be feasible to provide a similar fix to the tss implementation to avoid the compilation problem - e.g. ---- tss.hpp ----- ... extern "C" { typedef int (*pthread_<something>_cb_t)(void*); } ... class tss { ... ... tss(pthread_<something>_cb_t cb) ... --- end tss.hpp ---- Comments appreciated // Johan

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out of core property map and constant property map
by Joel Young 24 Aug '03

24 Aug '03

Has anyone created property maps that operate out of core? either against a database or a flat file? Would you like to share? Also has anyone created a property map that, once create returns a constant value for all queries (writable is nice, it doesn't do anything with the write of course)? This might be useful for compactly representing constant edge capacities. Finally, an out of core BasicMatrixConcept implementation for use with all-pairs shortest path on largish (n=1.6M, e=10*n) graphs would be handy. Thanks, Joel

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graph adapter from bidirectional to undirected
by Joel Young 24 Aug '03

24 Aug '03

Has anyone created a graph adapter to make a bidirectional graph appear as an undirected graph? If not, is the difficulty in making an edge iterator across both the in and out links? I particular I would like to compute a weak connected components on a bidirectional graph. So if you have a modified connected components alg for that it would be great. Thanks, Joel

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