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boost::function and template member functions
by Markus Werle 05 Dec '02

05 Dec '02

Hi! With the help of ConcreteEvoker I was able to get an (indirect) address for Test::Apply<double>. This address is obtained via automatic template instantiation, so I feel like there must be a way to achiev the same thing without ConcreteEvoker. Any comments? #include <iostream> #include "boost/function.hpp" #include "boost/bind.hpp" struct Test { template <class T> static T Apply(T t1, T t2) { return t1 + t2; } }; template <class T, class OP> struct ConcreteEvoker { static T Apply(T d1, T d2) { return OP::Apply(d1, d2); } }; int main() { boost::function<double (double, double)> test = &ConcreteEvoker<double, Test>::Apply; std::cerr << test(1.0, 2.0) << std::endl; }

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to add a function to the BGL
by Ramón Casero Cañas 05 Dec '02

05 Dec '02

Let's say I've written a function to prune edges of a graph (data structures and methods are those of the BGL), in the typical C-way (declare the function header in a .h file, and write the code in the .c file). Ok, it works, but I'm not fully satisfied. I would like to make it more BGL-like. So I use templates for generic graphs, include concept check lines in my code, and I have to forget about the .h and .c style, as templates behave a little like macros, and you cannot split the declaration and definition in two files. But, is there a better way to do this, like when you add you own internal property to the graph with BOOST_INSTALL_PROPERTY? Regards, Ramón.

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object_pool use ordered_malloc ordered_free. why?
by wugui 05 Dec '02

05 Dec '02

boost_1_28_0 if construct only, and freeall in ~object_pool. i think it is good. can i use object_pool to replace 'new delete'? the destroy is slow. thank for any advice. newbie and not good at english. full test code: #include <boost/pool/object_pool.hpp> #include <vector> #include <iostream> #include <time.h> #include <stdlib.h> struct Some { std::string ss; int ii; char cc[32]; }; int main(int argc, char * argv[]) { boost::object_pool<Some> pool; std::vector<Some*> v_Some; int count = 20000; time_t t = time(0); std::cout << ctime(&t) << std::endl; for (int i=0; i<count; ++i) { Some * s = pool.construct(); if (s) v_Some.push_back(s); else break; } t = time(0); std::cout << v_Some.size() << ctime(&t) << std::endl; if (argc > 1) { // fast for (std::vector<Some*>::reverse_iterator it = v_Some.rbegin(); it != v_Some.rend(); ++it) pool.destroy(*it); } else { // slow for (std::vector<Some*>::iterator it = v_Some.begin(); it != v_Some.end(); ++it) pool.destroy(*it); } t = time(0); std::cout << ctime(&t) << std::endl; return 0; }

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RE: [Boost-Users] Boost.Threads question
by James Zappia 04 Dec '02

04 Dec '02

Thank you, that worked. I see what I was doing wrong. One thing I don't understand about the alternative method... > boost::try_mutex::scoped_try_lock lock(mutex); // does a try_lock > while (!lock) { > cout << "trying..."; > lock.try_lock(); > } How does "!lock" in the "while (!lock) { ... }" statement determine whether it's true or false? Does it call a function in the scoped_try_lock class? (sorry if that's a lame question...) Thanks again for the help, very much appreciated. James Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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RE: [Boost-Users] Boost.Threads question
by James Zappia 04 Dec '02

04 Dec '02

> I'm a newbie to C++ and Boost and I'm trying to port a threaded C > program I have to Boost.Threads. I'm trying to use scoped_try_lock to > test a lock on mutex and it's not working. I'm obviously doing > something wrong but I can't figure it out. Below is the source code. > Any help would be greatly appreciated. >>How is it not working? What do you expect to happen? What I want to happen is that the main thread keeps trying the lock until it's freed. > SOURCE: > > #include <iostream> > #include <boost/thread/thread.hpp> > #include <boost/thread/exceptions.hpp> > > using namespace std; > > boost::try_mutex mutex; > > void thread_test( void ) > { > cout << "thread: locking mutex\n"; > > { > boost::try_mutex::scoped_try_lock lock(mutex); > cout << "thread: sleeping for 10 seconds\n"; > sleep(10); > } > > cout << "thread: unlocked mutex - goodbye!\n"; > > return; > } > > int main( void ) > { > cout << "main: creating thread\n"; > boost::thread thread(thread_test); > > cout << "main: sleeping for 2 seconds\n"; > sleep(2); > > cout << "main: trying to lock mutex\n"; > boost::try_mutex::scoped_try_lock lock(mutex,true); >>This will force a lock (which means we'll block until the thread releases >>the lock). > while ( !lock.try_lock() ) >>Since the above insured the mutex is already locked, this would be a >>recursive lock which should result in a thread_lock_error exception being >>thrown. Is this not what's happening for you? That is what's happening. As stated above, what I would like to happen is the main thread continuously try the lock until it's freed. What am I doing wrong? Thanks for the help! James > cout << "main: retrying to lock mutex\n"; > > cout << "main: joining thread\n"; > thread.join(); > > cout << "main: thread joined\n"; > return 0; > } >>William E. Kempf Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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Boost.Threads question
by James Zappia 04 Dec '02

04 Dec '02

Hi, I'm a newbie to C++ and Boost and I'm trying to port a threaded C program I have to Boost.Threads. I'm trying to use scoped_try_lock to test a lock on mutex and it's not working. I'm obviously doing something wrong but I can't figure it out. Below is the source code. Any help would be greatly appreciated. Thanks, James SOURCE: #include <iostream> #include <boost/thread/thread.hpp> #include <boost/thread/exceptions.hpp> using namespace std; boost::try_mutex mutex; void thread_test( void ) { cout << "thread: locking mutex\n"; { boost::try_mutex::scoped_try_lock lock(mutex); cout << "thread: sleeping for 10 seconds\n"; sleep(10); } cout << "thread: unlocked mutex - goodbye!\n"; return; } int main( void ) { cout << "main: creating thread\n"; boost::thread thread(thread_test); cout << "main: sleeping for 2 seconds\n"; sleep(2); cout << "main: trying to lock mutex\n"; boost::try_mutex::scoped_try_lock lock(mutex,true); while ( !lock.try_lock() ) cout << "main: retrying to lock mutex\n"; cout << "main: joining thread\n"; thread.join(); cout << "main: thread joined\n"; return 0; }

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compose, bind and a doubled ref problem
by Markus Werle 04 Dec '02

04 Dec '02

Hi! The code below compiles fine if You return to Value semantics and replace "const Vector&" with "Vector". But with reference to vector two compilers (Intel-7.0 and gcc-3.2.1) "throw" with a "reference to reference" error. How can I achieve what I want here? Do I have to apply cref somewhere? I do not want to change the type of "l" in this example. Also the signature of Vector::operator() and GetValue is fixed. Anything else may undergo a change. #include <iostream> #include <cstddef> #include "boost/function.hpp" #include "boost/bind.hpp" #include "boost/compose.hpp" struct Vector { double operator()(size_t j) const { std::cerr << "get value at index " << j << std::endl; return 99.0; } }; double GetValue(const Vector& V, size_t j) { return V(j); } double Add(double d1, double d2) { return d1 + d2; } int main() { using namespace boost; Vector V; function<double (const Vector&, size_t)> g = GetValue; function<double (const Vector&)> h1 = bind(g, _1, 5); function<double (const Vector&)> h2 = bind(g, _1, 4); function<double (double, double)> Adder = Add; function<double (const Vector&)> l = compose_f_gx_hx(Adder, h1, h2); std::cerr << l(V) << std::endl; }

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error linking debug version boost_regex with Solaris compiler
by kurt_zhang 03 Dec '02

03 Dec '02

I compiled boost_regex lib on Solaris using the following compiler: > CC -V CC: Sun WorkShop 6 update 2 C++ 5.3 2001/05/15 The version without using -g links fine, however, when I compiled the lib with -g option using provided makefile sunpro_dbx.mk, the lib was built OK; then I tried to compile provided test programs using libs/regex/test/regress/sunpro_dbx.mk, I got the following error: > make -f sunpro_dbx.mak mkdir -p r mkdir -p rm rm -f *.o rm -fr SunWS_cache CC -I../../../../ -I./ -L../../build/sunpro_dbx -g -o r/regress tests.cpp parse.cpp regress.cpp -lboost_regex tests.cpp: parse.cpp: regress.cpp: Undefined first referenced symbol in file boost::detail::allocator<unsigned char>::allocator<char>#Nvariant 1 (const boost::detail::allocator<__type_1>&) /fsys/home/zhangku/re/libs/regex/ test/regress/SunWS_cache/CC_obj_O/OhCenAP7d5aN-_Bfr3wh.o boost::detail::allocator<unsigned char>::allocator<wchar_t>#Nvariant 1 (const boost::detail::allocator<__type_1>&) ../../build/sunpro_dbx/libboost_r egex.so ld: fatal: Symbol referencing errors. No output written to r/regress make: *** [r/regress] Error 1 Can anyone help me on this? Kurt

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Lambda questions
by Claus Rasmussen 02 Dec '02

02 Dec '02

Is it possible to discern one-argument lambda expressions from two-argument expressions ? I would like to do something like this: template<typename UNARY_LAMBDA_FUNC> void f(UNARY_LAMBDA_FUNC ulf) { ulf(arg); } template<typename BINARY_LAMBDA_FUNC> void f(BINARY_LAMBDA_FUNC blf) { blf(arg1, arg2); } -Claus

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RE: [Boost-Users] Re: Extended use of BGL File Dependency Example
by Tom Matelich 02 Dec '02

02 Dec '02

From: David Abrahams [mailto:dave@boost-consulting.com] > Tom Matelich <tmatelich(a)zetec.com> writes: > > > From: David Abrahams [mailto:dave@boost-consulting.com] > > Sent: Sunday, December 01, 2002 5:58 AM > >> Tom Matelich <tmatelich(a)zetec.com> writes: > >> > >> > trying to make my graphviz representation look nicer and I > >> was wondering if > >> > there is an algorithm already for simplifying: > > > > -----B\ > > A--< \ > > --------C > > D----------/ > > > > to: > > > > A---B---C > > D------/ > > > > This eliminated the A-C edge. > > > > Thanks for considering my problem. > > Maybe you want a minimum spanning tree, where the weight of each edge > in the tree is determined by the distance between its vertices in some > topological sort? > > That seems to solve the cases shown above pretty nicely. I had looked at the minimum spanning tree docs a bit, I thought it looked pretty good. The docs say undirected graph though. I'm currently using a directed graph. I suppose I could create a separate graph. Oh, I see, create an undirected graph with weights as you said, and use the minimum spanning algorithm to choose the useful edges. I like it, hope it works. Thanks, Tom ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

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