- Boost-users - lists.boost.org

[fusion] iterating over a sequence with non-const references
by paul Fultz 04 Apr '12

04 Apr '12

Hi, I would like to iterate over a sequence and preserve the reference/const/non-const of the elements. That is say I have a sequence like this: tuple<int&, int> seq; I would like to this to be true: typeof(deref(begin(seq))) == int& typeof(deref(next(begin(seq)))) == int&& It seems fusion sequences always return a const reference to the element. Is there a workaround to get it to work like this? Or is this just not possible with Boost.Fusion? Furthermore, I would like to use the transformation algorithms (especially push_back, and push_front) and still preserve the reference type. Is that possible, through some workarounds? Finally, would it still be fairly efficient when dealing with references, to copy the tuple and make a new tuple when doing algorithms such as push_back or push_front? Or is the lazy evaluation much more efficient than that? Thanks, Paul Fultz II

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k-vertex-connectivity
by Martin 03 Apr '12

03 Apr '12

Hi, does anybody know a function to get the k-node-connectivity (k-vertex-connectivity) of a digraph (or graph)? (http://en.wikipedia.org/wiki/K-vertex-connected_graph) I could only find the function biconnected_components so far. Thanks, Martin

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Lambda and placeholders
by Sven Bauhan 02 Apr '12

02 Apr '12

Hi, I just tried to use boost::lambda to prevent from creating an extra Functor class just for one call. This is the code I tried: std::deque<LightningSlice>::const_iterator l = std::find_if( m_lightnings.begin(), m_lightnings.end(), boost::lambda::_1.timeslice().contains(time_) ); with typedef std::deque<LightningSlice> LightningQueue; LightningQueue m_lightnings; //!< The lightnings in timeslices const boost::posix_time::time_period& LightningSlice::timeslice() const { return this->m_period; } Then I get the error: ../LightningIndex.cpp:38: error: 'const struct boost::lambda::lambda_functor<boost::lambda::placeholder<1> >' has no member named 'timeslice' What did I wrong? Thanks, Sven

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regex_replace and Unicode ( Cyrillic ) problem
by valery O 02 Apr '12

02 Apr '12

Hi, I have a string with 2 Cyrillic words новый дом repeated 3 times. I try to regex_replace each occurrance of these words. For this I use std:: string format("$1 красный $2") and regex pattern ("(\\W+)\\s+(\\W+)"), The result is only the last occurrence is replaced,the 2 preceding ones are not. Where is my mistake? My code: #include <iostream> #include <string> #include "boost/regex.hpp" using namespace std; int main(int argc, const char** argv) { std::string str( "новый дом, новый дом новый дом" ); regex regx("(\\W+)\\s+(\\W+)"); std::string format( "$1 красный $2"); cout<<"regex_replace :"<<regex_replace( str, regx, format ); return 0; } I use iMac Intel Core Duo, Mac OSX 10.6.8, IDE - Xcode 3.2.6 Thank you. egersheldster

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[move] Move c-tor template
by Szymon Gatner 01 Apr '12

01 Apr '12

Hi, I am implementing custom smart pointer with move semantics and I am having problems with implementing move constructor with template param. In fact clone_ptr presented in docs suffers from that issue also. This code: class B {} class D: public B {} clone_ptr<D> makeD(); void main() { clone_ptr<B> b = makeD() // gives "error C2440: 'initializing' : cannot convert from 'clone_ptr<T>' to 'clone_ptr<T>'" } adding template <class U> clone_ptr(BOOST_RV_REF(clone_ptr<U>) p) //Move constructor : ptr(p.ptr) { p.ptr = 0; } to clone_ptr class does not help. Additional c-tor seems to be ignored. How to fix that? Cheers, Simon -- Szymon Gatner The Lordz Games Studio www.thelordzgamesstudio.com

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Re: [Boost-users] [boost] [test] Am I supposed to be able to use std::wstring in BOOST_CHECK_EQUAL?
by Daniel Trebbien 01 Apr '12

01 Apr '12

Hello Michael, Unfortunately, not yet. std::wstring support in BOOST_CHECK_EQUAL is Ticket #1136 (Let BOOST_CHECK_EQUAL support std::wstring): https://svn.boost.org/trac/boost/ticket/1136 Daniel Trebbien On 2012-04-01, Michael Kochetkov <michael.kv(a)gmail.com> wrote: > Hello, > Am I supposed to be able to use std::wstring in BOOST_CHECK_EQUAL? > I.e. > std::wstring s1,s2; > BOOST_CHECK_EQUAL(s1,s2); > > -- > Michael Kochetkov > > > _______________________________________________ > Unsubscribe & other changes: > http://lists.boost.org/mailman/listinfo.cgi/boost >

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[parameter] Documented way to call arg-pack-accepting function generated by BOOST_PARAMETER_FUNCTION
by Jeremiah Willcock 01 Apr '12

01 Apr '12

Is there a documented way to call a function generated using BOOST_PARAMETER_FUNCTION with an explicit ArgumentPack? The "<f>_with_named_params" hinted at in the documentation does not seem to exist. -- Jeremiah Willcock

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newbie: my program can't find boost libraries
by sparsh mittal 31 Mar '12

31 Mar '12

Hello I am new to boost. In my RHEL linux (no root permission), my program does not find boost installation and says: *** Please install package libboost-filesystem to /home/myself/folder *** Please install package libboost-system to /home/myself/folder I installed latest boost using these instructions<http://www.boost.org/doc/libs/1_42_0/more/getting_started/unix-variants.htm…> . ./bootstrap.sh ----with-libraries=filesystem,system --prefix=/home/myself/folder ./bjam install Can you tell, what is wrong I am doing and anything to add in include path etc. My paths: echo $LD_LIBRARY_PATH /home/myself/folder/lib:/home/myself/ddrive/test/boost_1_49_0/stage/lib echo $CPLUS_INCLUDE_PATH /home/myself/folder/include/ My program has makefile: LD_LIBS += -lboost_filesystem -lboost_system (and others) Thanks and Regards Sparsh Mittal

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Boost container inspector in gdb (linux)...
by Shashank Prasad 31 Mar '12

31 Mar '12

I need to inspect the boost containers (unordered_map, unordered_set etc) in gdb (linux)? How can I do that? Similar stuff for STL containers is available at http://sourceware.org/gdb/wiki/STLSupport, but I couldn't find for Boost anywhere. Thanks a lot for your help!

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My homemade object pool
by 饭桶 31 Mar '12

31 Mar '12

Hi all Here is my objectpool implemention which inspired by boost pool. Which have following features. Features: 1.Allocate an object from pre-allocate memory, when free an object just put it back to pool. 2.Call object's contructor at pool memory allocating or get object from pool, or do nothing. 3.Call object's deconstructor when "delete" object if constructor's been calling at "new" object 3.Call object's deconstructor when destroy objectpool if constructor's been calling at memory allocating 4.Can pass an function object to be invoke when "new" object, this can be used as a constructor if object's constructor don't be invokded when "new" object 5.Thread safe can be enable/disable by tempalte parameter 6.Callback can be raw pointer is T is not inherit from enable_shared_from this can be shared_ptr vers vice. There are several tasks need to do, like the allnodesset can be generated at callring of foreach. Delegate memory allocating to allocator, etc.. The whole project and unit test can be found at https://maxsrecyclebin.svn.sourceforge.net/svnroot/maxsrecyclebin/objectpoo… Is there any comments? Thanks ////////////////////////////////////////////////////////////////////////////////////// #include <istream> #include <list> #include <boost/shared_ptr.hpp> #include <boost/bind.hpp> #include <set> #include <algorithm> #include <boost/type_traits.hpp> #include <boost/enable_shared_from_this.hpp> #include <boost/thread/pthread/mutex.hpp> namespace maxutility { enum InitialType {None,ObjInitial,PoolAllocate}; template <typename T> class DummyCallableObj { public: void operator ()(boost::shared_ptr<T> &ptr) { //do nothing } }; template<bool isthreadsafe> class obthreadlock; template<> class obthreadlock<true> { public: void lock(){obmutex.lock();} bool try_lock(){return obmutex.try_lock();} void unlock(){obmutex.unlock();} private: boost::mutex obmutex; }; template<> class obthreadlock<false> { public: void lock(){}; bool try_lock(){return true;}; void unlock(){}; }; template <typename T,bool isthreadsafe=false,typename InitalFunction=DummyCallableObj<T> > class ObjectPool { #define LOCAL_LOCK boost::lock_guard<obthreadlock<isthreadsafe> > lg(obthreadlock_); protected: /** * @brief Declaration for furture usage **/ typedef T Node; typedef std::list<char *> FRAGMENTTYPE; typedef std::list<Node *> NODELIST; public: ObjectPool(InitialType initialtype=ObjInitial,size_t initialsize=512,size_t maxsize=0) { busyCount=0; this->poolsize=0; this->initialtype=initialtype; this->maxsize=maxsize; extend(initialsize); } ObjectPool(InitalFunction initalFunction=DummyCallableObj<T>(), InitialType initialtype=PoolAllocate, size_t initialsize=512, size_t maxsize=0) //:ObjectPool(initialtype,initialsize,maxsize) //Delegating constructors, c++11 only { busyCount=0; this->poolsize=0; this->initialtype=initialtype; this->maxsize=maxsize; this->initalFunction=initalFunction; extend(initialsize); } ~ObjectPool() { if(0!=busyCount) throw new std::exception(); if(PoolAllocate==initialtype) for(Node *p:allnodes) p->~Node(); for(char *pFragment:fragments) delete pFragment; } virtual boost::shared_ptr<T> create() { LOCAL_LOCK; boost::shared_ptr<T> ptr(static_cast<T*>(getFreeNode()),boost::bind(&ObjectPool<T,isthreadsafe,InitalFunction>::free,this,_1)); initalFunction(ptr); return ptr; } bool empty() { return !busyCount; } size_t size() { return busyCount; } size_t capacity() { return poolsize; } template <typename FUNCTION> void foreach(FUNCTION f) { LOCAL_LOCK; NODELIST freenodes=this->freenodes; //make a local copy freenodes.sort(); NODELIST busynodes(allnodes.size()); typename NODELIST::iterator busynodesend=std::set_difference( allnodes.begin(),allnodes.end(),freenodes.begin(),freenodes.end(),busynodes.begin() ); for(typename NODELIST::iterator iter=busynodes.begin(); iter!=busynodesend; iter++) { invokeFunction<FUNCTION,Node, boost::is_base_of<boost::enable_shared_from_this<Node>,Node >::value >()(f,*iter); } } protected: template<typename _Function,typename N,bool isuseshareptr> class invokeFunction; template<typename _Function,typename N> class invokeFunction<_Function,N,false> { public: void operator ()(_Function __f,N *p) { __f(p); } }; template<typename _Function,typename N> class invokeFunction<_Function,N,true> { public: void operator ()(_Function __f,N *p) { boost::shared_ptr<N> ptr=p->shared_from_this(); __f(ptr); } }; protected: void free(T *p) { LOCAL_LOCK; if(!p) return; destroyObj(static_cast<Node*>(p),ObjInitial); //removeBusyNode(static_cast<Node*>(p)); freenodes.push_back(static_cast<Node*>(p)); busyCount--; } Node *getFreeNode() { Node *ptr=nullptr; if(freenodes.empty()) //no new free node if(!extend()) //try to extend return ptr; //false ptr=freenodes.front(); //now it must contain free node freenodes.pop_front(); constructObj(ptr,ObjInitial); busyCount++; return ptr; } bool extend(size_t size=0) { if((0!=maxsize&&poolsize>=maxsize&&poolsize!=0) ) return false; //we reach the maximum size //poolsize=0 first allocation //size=0 extend twice size of current size //poolsize=size=0 we got a problem size_t extSize=((0==poolsize)?size:2*poolsize); char *pFragment=new char[extSize*sizeof(Node)]; if(!pFragment) return false; fragments.push_back(pFragment); poolsize+=extSize; for(Node *p=(Node*)pFragment; extSize--; p++) { constructObj(p,PoolAllocate); freenodes.push_back(p); allnodes.push_back(p); } allnodes.sort(); return true; } void constructObj(Node *p,InitialType phase) { if(phase==initialtype) ::new(p)Node; } void destroyObj(Node *p,InitialType phase) { if(phase==initialtype) p->~Node(); } size_t poolsize; InitialType initialtype; size_t maxsize; FRAGMENTTYPE fragments; NODELIST freenodes; NODELIST allnodes; size_t busyCount; InitalFunction initalFunction; obthreadlock<isthreadsafe> obthreadlock_; }; };

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