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binding a member variable?
by Russell Hind 05 Aug '04

05 Aug '04

Is it possible to have a member variable in a bind expression or do I need to have an accessor method for the variable? E.g. I have the following structure and I want to use min_elemnt to find the point with the lowest m_Z value in a vector. class Point_c { public: double m_X; double m_Y; double m_Z; } Thanks Russell

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question about an implementation detail in boost::shared_ptr
by Jeff Williams 04 Aug '04

04 Aug '04

I was reading through the boost::shared_ptr source code, and I have a question about one small detail. This is in boost release 1.31.0: Around line 84 we have this code: // enable_shared_from_this support template<class T, class Y> void sp_enable_shared_from_this(boost::enable_shared_from_this<T> * pe, Y * px, shared_count const & pn) { if(pe != 0) pe->_internal_weak_this._internal_assign(px, pn); } I was curious, why is this function not inline? Jeff

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RE: [Boost-users] Re: Looking for some help with boost::thread::sleep()
by Kutch, Patrick G 04 Aug '04

04 Aug '04

Not a problem. It looks as if it goes into the # elif defined(BOOST_HAS_NANOSLEEP) section. Patrick Kutch Life is too short to drink bad coffee. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Michael Glassford Sent: Tuesday, August 03, 2004 4:20 PM To: boost-users(a)lists.boost.org Subject: [Boost-users] Re: Looking for some help with boost::thread::sleep() Kutch, Patrick G wrote: > Has nobody else experienced this? Sorry, I forgot all about answering your original post. If you look at the thread::sleep() method, it looks like the following; can you tell me which path it's taking (there are several options for pthreads) when you have the problem? void thread::sleep(const xtime& xt) { for (int foo=0; foo < 5; ++foo) { #if defined(BOOST_HAS_WINTHREADS) int milliseconds; to_duration(xt, milliseconds); Sleep(milliseconds); #elif defined(BOOST_HAS_PTHREADS) # if defined(BOOST_HAS_PTHREAD_DELAY_NP) timespec ts; to_timespec_duration(xt, ts); int res = 0; res = pthread_delay_np(&ts); assert(res == 0); # elif defined(BOOST_HAS_NANOSLEEP) timespec ts; to_timespec_duration(xt, ts); // nanosleep takes a timespec that is an offset, not // an absolute time. nanosleep(&ts, 0); # else mutex mx; mutex::scoped_lock lock(mx); condition cond; cond.timed_wait(lock, xt); # endif #elif defined(BOOST_HAS_MPTASKS) int microseconds; to_microduration(xt, microseconds); Duration lMicroseconds(kDurationMicrosecond * microseconds); AbsoluteTime sWakeTime(DurationToAbsolute(lMicroseconds)); threads::mac::detail::safe_delay_until(&sWakeTime); #endif xtime cur; xtime_get(&cur, TIME_UTC); if (xtime_cmp(xt, cur) <= 0) return; } } Mike _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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RE: [Boost-users] Looking for some help with boost::thread::sleep()
by Kutch, Patrick G 03 Aug '04

03 Aug '04

Has nobody else experienced this? Patrick Kutch Life is too short to drink bad coffee. -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Kutch, Patrick G Sent: Thursday, July 22, 2004 8:07 PM To: boost-users(a)lists.boost.org Subject: [Boost-users] Looking for some help with boost::thread::sleep() I am used to putting in quick sleep() statements in my worker threads, usually a sleep(0) just to give up a timeslice, or maybe a sleep(1). Of course boost::thread::sleep takes an xtime object not a milliseconds value, so I wrote a small routine to simulate the sleep() statement using boost::thread::sleep: void inline UtilitySleep(long milliSeconds) { const int NANOSECONDS_PER_MILLISECOND = 1000000; if (0 == milliSeconds) { boost::thread::yield(); // just do a yield return; } boost::xtime time; int sec = 0; // if larger than 1 sec, do some voodoo for the boost::xtime struct if (milliSeconds >= 1000) { // convert ms > 1000 into secs + remaining ms int secs = milliSeconds /1000; milliSeconds = milliSeconds - secs*1000; sec += secs; } milliSeconds*=NANOSECONDS_PER_MILLISECOND; // normal boost time sleep stuff // get current time boost::xtime_get(&time,boost::TIME_UTC); // add # of desired secs and ms time.nsec+=milliSeconds; time.sec+= sec; // sleep until that time boost::thread::sleep(time); } It seems to always work fine unde Windows, however occasionally under Linux it appears that if I use a small value, such as sleep(2) that sometimes it takes longer to setup the values and call boost::thread:sleep() and I end up passing an xtime value that has already passed, basically blocking the thread forever. Anybody have any advice for me? Thanx! - Patrick _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Looking for a simple example of instantiating normal_distribution from the random library correctly
by Kuntz, David A 03 Aug '04

03 Aug '04

> I am instantiating normal_distribution from the random > library incorrectly and looking for a simple example of how to do it > correctly. > > I compiled, built and ran random_test.cpp and can see > when I step through the normal_distribution () operator that _r1 and > _r2 have values < 1. > > Here are the relevant excerpts from my incorrect attempt > at instantiation and calling the () operator: > > typedef boost::mt19937 base_generator_type; > > boost::uint32_t x = 42u; > Ideal4045EsmModel::base_generator_type > base_generator(x); > > double randomDrawResult; > > boost::normal_distribution<double> boostNormalRand; > > boostNormalRand.reset(); > > randomDrawResult = boostNormalRand(base_generator); > > This compiles, builds, and runs, but when I step through > the normal_distribution () operator, _r1 and _r2 have very large > positive values, resulting in an attempt to take the log of a > negative number and an Indefinite value being returned. > > I am a relatively inexperienced C++ developer. I have > built and stepped through random_test.cpp > (http://www.boost.org/libs/random/random_test.cpp) and can see that > its gets correct results, but I found it quite difficult to follow. Is > there anyone out there who could show me a simpler way? > > Thanks, > > Dave > > > >

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Bidirectionnal filtered multigraph
by Robert weldon 03 Aug '04

03 Aug '04

I've created a bidirectional filtered multigraph from an adjacency_list with vectorS and listS as containers for the vertices and egdes respectively. It seems the function edge(u,v,g) does not work properly for this kind of graph. I can detect the existence of an edge (u,v) if I iterate explicitly through the out_edges of the filtered graph but not if I use edge() directly on the filtered graph. Also, I get an exception when I remove an edge that was invisible to the edge(u,v,g) function while the bidirectionnal version of remove_edge for adjacency_list is erasing the edge ID form the in_edge list of the graph. Any idea why edge() does not work in this case? Patrick --------------------------------- Do you Yahoo!? New and Improved Yahoo! Mail - Send 10MB messages!

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Print all routes in a graph
by Daniele Carlucci 03 Aug '04

03 Aug '04

Hi all, I have seen the mail with dijikstra algorithm, there is a way to print all the routes in a graph from a node A and a node B? Thanks Daniele Carlucci

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Function Adaptor that takes an Address
by Ewan Mellor 03 Aug '04

03 Aug '04

I have a function T & foo() and I wish to use a function adaptor to turn this into T * foo2() In other words, I want a function adaptor that takes the address of its given function's result. Does such a thing exist in boost? TIA, Ewan Mellor.

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[BGL] Importing adjacency list from a txt file
by Rui Carvalho 03 Aug '04

03 Aug '04

Hi, I've got a file with the adjacency list of a graph, where each line contains the node index followed by the index of nodes that are adjacent to it (comma-separated). One of the lines of this file could read like: 1,3,4 This would mean that node '1' is adjacent to nodes '3' and '4' (undirected & unweighted graph). I'm declaring it as: typedef adjacency_list < vecS, vecS, undirectedS, no_property, no_property > Graph; Graph g; My question is: is there a simple way of reading the adjacency list into the graph from my txt file? I found Kevin_Bacon, but was looking for something more powerful. Then I found adjacency_list_io.cpp (is it documented?), but it wouldn't compile on MSVC. Am I missing something obvious? Thanks, Rui

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bind and weak pointers
by Jeff Williams 02 Aug '04

02 Aug '04

What is the prefered method of creating a boost::function<void()>, via boost bind, that is calling a member function of a class, and that class instance is held inside the bind object as a weak ptr. Thus, when the function is called, it will try to lock the shared_ptr, if successful it calls the bound function, otherwise it does nothing. Is there an standard way of doing this? Or do I have to write my own custom intermediate function? (which is how I do it now). Jeff

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