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[Bind] Is this how to write it?
by Robert Jones 24 Mar '10

24 Mar '10

Hi All In this bit of code.... #include <algorithm> #include <vector> #include "boost/bind.hpp" struct A { int double_it( int i ) { return i * 2; } } a; std::vector< int > v; int main( ) { for ( std::vector< int >::iterator i = v.begin( ); i != v.end( ); ++ i ) { a.double_it( * i ); } // Write it as a for_each/bind std::for_each( v.begin(), v.end(), boost::bind( & A::double_it, boost::ref( a ), _1 ) ); } Is that last line the idiomatic way of writing the bind expression? Thanks, Rob.

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shared_memory_object constructor
by Just C 24 Mar '10

24 Mar '10

I find shared_memory_object constructor semantics to be rather inconvenient for embedding it into another class. Consider the following class A { public: A(int type) : shm_(pass params to the shared_memory_object ctor) { } private: shared_memory_object shm_; }; If my class A is such that a shared_memory_object needs to be called with either create_only or open_only based on the type passed to A's constructor, I can't do it easily. i.e. some thing like A(int type) : shm_(type == something ? create_only : open_only) {} This won't work because create_only & open_only are different types & this will call 2 different overloaded constructors, hence the above code will not compile. Alternatives here are 1) make A a templated class instead of having type as a ctor param. i.e. template <class T> class A { public: A() : shm_(T(), other params) {} }; then use A<create_only> a; A<open_only> b; OR 2) Keep a shared_memory_object ptr inside non-templated class A instead of an actual object and create it dynamically. Assuming, I don't want to use either of these options, is there any other nifty trick anyone can think of to achieve what I want to do?

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shared_memory_object & managed_shared_memory
by Just C 24 Mar '10

24 Mar '10

This is what I am trying to do - I have to 2 processes in the same box. - I need to send a buffer of data from one process to another. - The other process reads the data & may want to send something back. - At any time there is only one such buffer in process - i.e. no queue of data to send. - the process will send a new buffer only when it gets acknowledgement back from the other process that it's finished reading it. I am a little unclear as to what I should use here - shared_memory_object or managed_shared_memory - it's not very clear what's the difference between the two. I tried out a sample from the condition_variable example here & it seems to work. http://www.boost.org/doc/libs/1_36_0/doc/html/interprocess/synchronization_… However, in the example the size of the shared memory is based on the size of the trace_queue object. In my case, the size needs to be configurable. so I am thinking of something like this - no data array inside the struct. struct data { data(void * p) : message_in(false), actualdata(p) {} //Mutex to protect access to data boost::interprocess::interprocess_mutex mutex; boost::interprocess::interprocess_condition cond_empty; boost::interprocess::interprocess_condition cond_full; void * actualdata; bool message_in; }; then shared_memory_object shm (create_only ,"shared_memory" ,read_write ); shm.truncate (sizeof(data) + myconfiguredsize); actual data is beyond the struct which holds the condition variable i.e. when i write data, i will do mapped_region region (shm ,read_write ); void * addr = region.get_address(); data * d = new (addr) data(addr); then //Use the condition_variables to protect the write & then memcpy memcpy(d->actualdata, thedataiwanttocopy, sizeofthedataiwanttocopy); Am I doing this the right way or is there a better way to go about this?

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A question on boost mpl used by MTL. Can any one with kindness help me?
by fmingu 24 Mar '10

24 Mar '10

I am using MTL(Matrix Template Library) 4 (the version is mtl4-beta-1-r6916) for Matrix computing in Dev-C++ 4.9.8.0 and updated the gcc version from 3.2 to 4.4.1 by installing tdm-mingw-1.908.0-4.4.1-2 and the boost version is 1.34.1. The sample code is : #include <boost/numeric/mtl/mtl.hpp> int main(int argc, char* argv[]) { using namespace mtl; using namespace mtl::matrix; const unsigned xd= 2, yd= 5, n= xd * yd; dense2D<double> A(n, n); compressed2D<double> B(n, n); hessian_setup(A, 3.0); laplacian_setup(B, xd, yd); typedef std::complex<double> cdouble; dense_vector<cdouble> v(n), w(n); for (unsigned i= 0; i < size(v); i++) v[i]= cdouble(i+1, n-i), w[i]= cdouble(i+n); v+= A * w; w= B * v; std::cout << "v is " << v << "\n"; std::cout << "w is " << w << "\n"; return 0; } But the complier tolde me that : ……………………………… F:\CB2009\boost_1_34_1\boost_1_34_1/boost/mpl/apply_wrap.hpp:81:31: error: missing binary operator before token "(" F:\CB2009\boost_1_34_1\boost_1_34_1/boost/mpl/apply_wrap.hpp:173:31: error: missing binary operator before token "(" ……………………………… And the code in the corresponding lines of apply_wrap.hpp are: …………………………. #elif BOOST_PP_ITERATION_DEPTH() == 1 ……………………… #elif BOOST_PP_ITERATION_DEPTH() == 2 And I do not know how to solve it. Can any one with kindness help me?

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[Boost-Users] Boost::Thread: scoped thread using boost::move
by Boost lzw 23 Mar '10

23 Mar '10

Hello folks, The following scoped_thread that I wrote runs well with boost 1.42.0: #include <boost/thread/thread.hpp> #include <iostream> class scoped_thread { boost::thread t; scoped_thread(const scoped_thread&); scoped_thread operator=(const scoped_thread&); public: scoped_thread(boost::thread t_) : t(boost::move(t_) ) { if (!t.joinable() ) throw; } ~scoped_thread () { t.join(); } }; However, as you may notice I did not include <move.hpp> and did use boost::move in the ctor. Is the true std::move semantics already available on boost 1.42.0 by just including <boost/thread/thread.hpp>? If so (as my code illustrates), that would be nice. Cheers, Robert

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[tokenizer] boost::tokenizer doesn't handle '/' properly?
by Naked Short Selling 23 Mar '10

23 Mar '10

Greetings, I'm trying to parse a csv file using boost tokenizer. But I see weird result when there are cells like "IG9/10/7-10:USCEFLCORR0001", tokenizer returns tokens like "IG9/,0/7-,0:USCEFLCORR000". I am assuming it's because of slash '/'. Here's my code snippet: " typedef boost::tokenizer<boost::char_separator<char> > tokenizer; char delim = ','; boost::char_separator<char> sep(&delim); ... tokenizer tokens(str, sep); tokenizer::iterator iter = tokens.begin(); tokenizer::iterator end = tokens.end(); " Please advise. Thanks!

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Re: [Boost-users] [proto] generation of adaptive precision floating-point geometric predicates
by Andrew Durward 23 Mar '10

23 Mar '10

Hi all, Seems I've made a little progress (see attached file) but it's still a long way from complete. I'm sure there are better/more generic ways to perform the type manipulation but I'm fairly new to boost.fusion as well. Comments and suggestions are welcome. Thanks for the help thus far, andrew

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newbie question on boost/graph library: how to use read_graphViz with bundled vertex/edge properties
by Rong She 23 Mar '10

23 Mar '10

I have declared CustomVertex and CustomEdge classes, each with a bunch of internal properties. class CustomVertex { int length; string name; bool ori; public: CustomVertex() {} ~CustomVertex() {} FlipVertex() { ori = !ori; } }; class CustomEdge { char type; int distance; bool src_ori; bool dst_ori; public: CustomEdge() {} ~CustomEdge() {} }; Tried to use bundled properties, the graph is defined as: typedef adjacency_list<vecS, vecS, directedS, CustomVertex, CustomEdge> myGraph; I want to read from a dot file (which contains all appropriate vertex, edge information) and populate the graph. I know I'm supposed to use dynamic_properties etc. Could someone show me how exactly? Thanks.

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Re: [Boost-users] [proto] need explanation in implementing distributive law
by Kim Kuen Tang 23 Mar '10

23 Mar '10

Hi Andrew, it compiles on my side. Thx for ur improvement. Cheers, Kim Andrew Durward schrieb: > As a follow-up, the attached code seems to compile and yield the expected > result. > > andrew > > ------------------------------------------------------------------------ > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users

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[iostreams] Flushing a zlib_compressor... how to obtain a “zlib sync flush” ?
by Tim Day 23 Mar '10

23 Mar '10

Is there some magic required to obtain a "zlib sync flush" when using boost::iostreams::zlib_compressor ? Just invoking flush on the filter, or strict_sync on a filtering_ostream containing it doesn't see to do the job (ie I want the compressor to flush enough that the decompressor can recover all the bytes consumed by the compressor so far, without closing the stream; I remember using such a feature when driving zlib directly in the past, and there's a page http://www.bolet.org/~pornin/deflate-flush.html describing it nicely). Looking at the header, there seem to be some "flush codes" defined (notably a sync_flush) but it's unclear to me how they should be used (bearing in mind my compressor is just added into a filtering_ostream's chain, although I do have a reference to it if some specific method needs invoking). Thanks for any tips. Tim

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