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GCC 3.2 compiler error using Boost::Threads::Mutex::scoped_lock
by Michael Hunley 05 Mar '03

05 Mar '03

Disclaimer: I am relatively new to gcc, linux and Boost. I'm hoping someone out in the group who is much more knowledgable about all of them can help me get past a hurdle in code I am porting from Windows. I am getting a vague error message from g++ (gcc 3.2-7 under Redhat Linux 8.0) in my code using the Boost scoped_lock. I have wrapped the Boost versions of mutex and mutex::scoped_lock as: class PMutex { public: PMutex() {} virtual ~PMutex() {} protected: boost::mutex m_Mutex; friend class PScopedLock; }; class PScopedLock { public: explicit PScopedLock( PMutex& M ) : m_ScopedLock(M.m_Mutex) {} virtual ~PScopedLock() {} static PScopedLock* Create( PMutex& M ) { return (PScopedLock*) ::new PScopedLock(M); } void Destroy( void ) { delete this; } protected: void* operator new(size_t) {} // disallowed, must declare on the stack boost::mutex::scoped_lock m_ScopedLock; friend class PCondition; }; The error is "ISO C++ forbids declarations of 'type name' with no type". I get that error on several lines, but most notably on a simple declaration like: PScopedLock Lock(MyMutex); From what little I can find on the newsgroups, this sort of error has been noted when use of template template parameters are not declared quite correctly (without the trailing ::template from what I can gather). But as far as I can tell, I should not be having that issue. I am not knowledgeable enough about templates, Boost or gcc/g++ to sort out what I am running into. Boost builds fine under gcc, the code I am porting compiles fine under MSVC6 and Kylix3, but not gcc. Can anyone help me out? thanks. michael

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Has anyone compiled Boost successfully on OS390?
by kant_rakesh <kant_rakesh＠yahoo.com> 05 Mar '03

05 Mar '03

Hi, I am trying to get boost compiled on OS390. Has anyone done it successfully so far? The compiler on OS390(version2 release10) is complaining of empty template parameter. It does not like 'template <>', which is being used frequently in the library. Any ideas about how to successfully build this on OS390? Thanks and Regards Rakesh Kant

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boost-users@lists.boost.org ?
by speedsnaii <speedsnaii＠yahoo.de> 04 Mar '03

04 Mar '03

I tried to subscribe to the list boost-users(a)lists.boost.org I was thinking that this is just an alias list of this one. But it seems not to be true, is it? I would prefer to use the mail interface. Can anyone enligthen me if this is possible, please? Thank you, roland

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uBLAS: reference to container data & iterator declaration
by Roland Schwarz 04 Mar '03

04 Mar '03

Hi, *) First question: I am trying to get a reference to data of a container in the following way: matrix<double> m(3,3); vector<double>& v(m.column(2)); But this seems not to be possible. Is there a way to achieve this behaviour? What I basically want to achive is having functor object that holds a reference to a row/column of my container matrix. >From my questions about argument types I know that m.column(2) is a kind of an expression. How can I get the underlying reference to data if there even is one? *) Second question: matrix<double> m(10,3); ... fill the matrix ... matrix<double>::iterator it; // wrong this does not work!! for (it = m.column(2).begin(); it != m.colum(2).end(); ++it) { cout << *it << " " << foo(*it) << endl; } How would I declare my iterator? I understand when I use std::library-algorithms the automatic template parameter defer will give me the correct type from begin(). But in my case how should I declare the iterator? Thank you for help. Roland

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multivoque application algorithms
by Alexandre Carsac 03 Mar '03

03 Mar '03

I applologize, perhaps this is the wrong place, Just wondering if the boost Graph library can be used for multivoque application. ------------------------------------------------------------------------------------------- let be : E = {x0, x1, ...,xp} F = {y0, y1, ...,yq} G': y -> {xa.....xm} and card G'(y) = constant = m G : x -> {ya.....yn} and card G(x) < M for all x belongs to E G' is the reverse application of G. G is irregular. h : x -> h(x) whose values are in [0,1] The problem is to find the y0 so that G'(y0) maximise h(xa), ...,h(xm). (assume that h(xi) near of 1 for all xi in G'(y0) ) One simple approch would be to calculate h(x) for all x associated to all y and keep the maximum, but this lead to too much calculations. ------------------------------------------------------------------------------------------------- I try to organized E into a binary tree. The idee is to shrink E so that each schink step truncate the search space. lets take x0 so that card G(x0) be maximum. We have the composed application of G with its reverse one G': G o G' (x0) = {xaa....xpa, xab,...xpb, xpa,....xpn} means that x0 is tied to some other x's in E by G. if h(x0) is the not near 1, then the y we are looking for will have fewer chance to belongs to G'(x0), so it is not worth to look at all the h(xaa), ...h(xpn). This would create a bi-partion on E and so on. --------------------------------- Do You Yahoo!? -- Une adresse @yahoo.fr gratuite et en français ! Testez le nouveau Yahoo! Mail [Non-text portions of this message have been removed]

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Re: [Boost-Users] stop a thread
by William E. Kempf 03 Mar '03

03 Mar '03

> From: "hlh771 <hlh771(a)yahoo.com.cn>" <hlh771(a)yahoo.com.cn> > > How to stop(or cancel) a thread? Suppose I have a main thread and a > worker thread, the worker thread does something looply,and when the > main thread get a message indicating the process should exit, I want > stop the worker thread,how to do that?I have read other thread > library,their thread class supply a method called stop or cancel > which stops the thread. Their Implementation is:the thread class has > a data member indicating whether the thread should stop,and the > thread function looply check the data member whether the thread > should stop.Generally the data member's type is a bool or Event. > Is it the best way to stop the thread? How the boost to deal with > this? > Thanks in advance. Today you should use a flag and a condition/mutex combination. Direct support for cancellation is being provided in a future release. William E. Kempf wekempf(a)cox.net

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Exporting references into boost::python
by Nicholas Francis 02 Mar '03

02 Mar '03

A newbie question regarding boost::python. I need to make a templatized function that returns a boost::python::object containing a reference to an object I already have. Basically: template<class T> object convertToPython (T &obj) { return object (obj) } All classes I pass through T are already wrapped (they are also not copy-constructible). I tried with the code found at python.orgs wiki: template<class T> T& identity(T& x) { return x; } template<class T> object get_object_reference (T& x) { object f = make_function (&identity<T>, return_value_policy<reference_existing_object()); return f(x); } this code gave me a compile error (on CW 8.3, Mac OS X). Apparently CW is convinced that the &identity<T> maps to void. I then tried to hardcode a type just to see if it worked at all: InputManager &identity (InputManager &x) { return x; } object get_object_reference (InputManager &x) { object f = make_function ( &identity, return_value_policy<reference_existing_object()); return f(x); } This compiled, but gave me a typeerror at runtime: (No to_python (by-value) converter found for c++ type: InputManager) I've seccesfully wrapped functions like this: InputManager &GetInputManager(); BOOST_PYTHON_MODULE (Engine) { def ( "GetInputManager", &GetInputManager, return_value_policy<reference_existing_object() ); } So it should be able to work. Any help would be greatly appreciated.... TIA, Nicholas

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VC7 says 'fatal C1067' compiling multi_array?
by Clift Norris 01 Mar '03

01 Mar '03

Greetings: I'm using VC7 and boost_1_29_0 to compile this code that is using multi_array.hpp. typedef boost::multi_array<double, 4> theta4_t; typedef theta4_t::index index; theta4_t Theta_Trun( boost::extents[10000][2][10][256] ); I'm receiving this error: "fatal error C1067: compiler limit: debug information module size exceeded" Of course, the code compiles fine using the "Release" configuration, but I need the "Debug" one also. Is there a workaround for this, other than the 'make your variables shorter' suggested in the VC7 documentation? Thanks, -Clift

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are namespaces of boost libs required to be lowercase?
by Markus Werle 28 Feb '03

28 Feb '03

Hi! If someone wants to contribute code to boost: Is she required to provide the names of all namespaces lowercase? E.g. someone provides Elefant, the big library. Is she allowed to have namespace Elefant and perhaps namespace Elefant::Private, etc. I could not find any hint except this here, which did not really help me, since I do not know the standard library's conventions. Any link/ hint appreciated: -- citation from the boost docs -- "Naming conventions rationale The C++ standard committee's Library Working Group discussed this issue in detail, and over a long period of time. The discussion was repeated again in early boost postings. A short summary: Naming conventions are contentious, and although several are widely used, no one style predominates. Given the intent to propose portions of boost for the next revision of the C++ standard library, boost decided to follow the standard library's conventions." best regards, Markus

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poisson_distribution header file
by kgolod0641 <kgolod＠engmail.uwaterloo.ca> 28 Feb '03

28 Feb '03

Hi, I am using boost_1_29_0 to implement random distribution functions. The standard download included implementation of uniform, normal and exponential distributions - and they work great. I also need an implementation of poisson distribution, and I have noticed that poisson_distribution.hpp was added to CVS last October. I got the file, and put it into the boost/random/ directory, with the other random distribution files. However, when I try using poisson distribution, I get a series of 0's instead of a series of random numbers, although I'm using it exactly the same way as with the other distributions. I am not sure whether the problem is due to incorrect installation of the new file, or due to bugs in the implementation. I tried cleaning the boost_1_29_0 directory, and running bjam again, but still no luck. Is there anything else I should do to include this new header file? Any help would be greatly appreciated. Thank you, Ksenia

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