August 2009 - Boost-users - lists.preview.boost.org

2d array arg, f( int m, int n, int a[m][n] ) with multi_arrays ?
by Denis-B 11 Aug '09

11 Aug '09

Folks, how can I do the following with multi_arrays please ? void f( int m, int n, int a[m][n] ) // legal C99 ? dunno -- would be nice { ... a[j][k] = ... } ... int *a; // m*n ints, e.g. an image f( m, n, a ); thanks, cheers -- denis -- View this message in context: http://www.nabble.com/2d-array-arg%2C-f%28-int-m%2C-int-n%2C-int-a-m--n--%2… Sent from the Boost - Users mailing list archive at Nabble.com.

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[Serialization] Stream error when serializing float and unsigned int
by D Kruithof 10 Aug '09

10 Aug '09

Hello All, When serializing this class: class { float a; unsigned int b; }; i get a stream error upon de-serializing, when 'a' has the value infinity. Is this a bug? I included a (very small) program which shows the error. It crashes on iteration 3. I use the mingw 3.4.5 compiler with boost 1.38 (no changes have been made to serialization since 1.38) on windows XP. Thanks, D Kruithof

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[mpi] building boost::mpi libs
by James C. Sutherland 10 Aug '09

10 Aug '09

I have successfully built the boost MPI libraries on my mac. When trying on Linux I am having problems with the compiler not including the path for mpi.h. For example, I get errors like: > gcc.compile.c++ bin.v2/libs/mpi/build/gcc-3.4.6/release/threading- > multi/python/datatypes.o > In file included from ./boost/mpi/python/config.hpp:15, > from ./boost/mpi/python/serialize.hpp:23, > from libs/mpi/src/python/datatypes.cpp:13: > ./boost/mpi/config.hpp:20:17: mpi.h: No such file or directory I am not familiar with bjam. My MPI installation is in a non-standard location and I added > using mpi : /uufs/chpc.utah.edu/sys/pkg/mpich2/std/bin/mpicxx ; to my user-config.jam file. How do I tell bjam to look somewhere special for the mpi headers? Thanks for any tips. James

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[statechart] Non-Const Machine Pass-throughs and state_cast
by Grant Erickson 10 Aug '09

10 Aug '09

I am using Boost::Statechart for the first time, throwing in the bin a history of hand-coded and other class-based implementations of my own design, to realize a rather simple machine consisting of four events (start/stop/suspend/resume) and four states (stopped/running/stopped-suspended/running-suspended). The machine is effectively a timer and wraps another internal timer class that can be stopped/started and suspended/resumed. This is all the machine does. The internal timer class can get/set its interval and can also get/set a delegate, that is called (if set) when the timer fires. These internal timer management interfaces are "passed through" to the state machine interface, such that application/test code is as follows: ...(TimerDelegate & inDelegate, float inInterval) { Timer theTimer; theTimer.initiate(); BOOST_ASSERT(!theTimer.IsSuspended()); BOOST_ASSERT(!theTimer.IsRunning()); DisplayState(theTimer); theTimer.SetDelegate(inDelegate); theTimer.SetInterval(inInterval); cout << "The delegate is " << theTimer.GetDelegate() << endl; cout << "The interval is " << theTimer.GetInterval() << endl; BOOST_ASSERT(!theTimer.IsSuspended()); BOOST_ASSERT(!theTimer.IsRunning()); DisplayState(theTimer); theTimer.process_event(Events::Start()); BOOST_ASSERT(!theTimer.IsSuspended()); BOOST_ASSERT(theTimer.IsRunning()); DisplayState(theTimer); The delegate does the real work of the program and receives events that drive the timer machine. Where I have run into a problem is that my machine "pass through" setter methods allowing the delegate to be set or the timer interval to be changed (neither of which materially alter the state of the machine) cannot be called as they are non-const qualified whereas their corresponding getters work fine since they are const qualified. I've worked around this in the short term by qualifying the setters as const and then qualifying the data members as mutable; however, this strikes me as flat-out ugly and wrong. Is there a better way to accomplish this? Am I misusing the template/design pattern? I suppose I could applying a const_cast(); however, that seems just as bad as my existing workaround. class InternalTimer; struct TimerDelegate { virtual void TimerDidFire(const InternalTimer &inTimer) const = 0; }; class InternalTimer { public: InternalTimer(void); : ~InternalTimer(void); TimerDelegate *GetDelegate(void) const; float GetInterval(void) const; void SetDelegate(TimerDelegate *inDelegate); void SetInterval(float inInterval); void Start(void); void Stop(void); private: TimerDelegate * mDelegate; float mInterval; }; struct ITimerManagement { public: virtual TimerDelegate *GetDelegate(void) const = 0; virtual float GetInterval(void) const = 0; virtual void SetDelegate(TimerDelegate * inDelegate) = 0; virtual void SetInterval(float inInterval) = 0; }; struct IRunning { public: virtual bool IsRunning(void) const; protected: IRunning(bool inRunning); private: bool mRunning; }; struct ISuspended { public: virtual bool IsSuspended(void) const; protected: ISuspended(bool inSuspended); private: bool mSuspended; }; struct Active; struct Timer : state_machine< Timer, Active > { public: TimerDelegate * GetDelegate(void) const { return (state_cast< const ITimerManagement & >().GetDelegate()); } float GetInterval(void) const { return (state_cast< const ITimerManagement & >().GetInterval()); } void SetDelegate(TimerDelegate *inDelegate) { state_cast< ITimerManagement & >().SetDelegate(inDelegate); // XXX } void SetInterval(float inInterval) { state_cast< ITimerManagement & >().SetInterval(inInterval); // XXX } bool IsRunning(void) const { return (state_cast< const IRunning & >().IsRunning()); } bool IsSuspended(void) const { return (state_cast< const ISuspended & >().IsSuspended()); } }; struct Timer; struct Stopped; struct Running; struct StoppedSuspended; struct RunningSuspended; struct Active : ITimerManagement, simple_state< Active, Timer, Stopped > { virtual TimerDelegate * GetDelegate(void) const { return (mInternalTimer.GetDelegate()); } virtual float GetInterval(void) const { return (mInternalTimer.GetInterval()); } virtual void SetDelegate(TimerDelegate *inDelegate) { mInternalTimer.SetDelegate(inDelegate); } virtual void SetInterval(float inInterval) { mInternalTimer.SetInterval(inInterval); } void Start(void) { mInternalTimer.Start(); } void Stop(void) { mInternalTimer.Stop(); } private: InternalTimer mInternalTimer; }; struct Running : IRunning, ISuspended, state< Running, Active > { public: typedef mpl::list< transition< Events::Stop, Stopped >, transition< Events::Suspend, RunningSuspended > > reactions; Running(my_context inContext) : my_base(inContext), IRunning(true), ISuspended(false) { context< Active >().Start(); } ~Running(void) { context< Active >().Stop(); } }; Regards, Grant

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Re: [Boost-users] [Accumulators] Questions about the library
by dhruva 10 Aug '09

10 Aug '09

Hello, > Date: Thu, 25 Jun 2009 03:41:49 -0700 (PDT) > From: adish > Subject: Re: [Boost-users] [Accumulators] Questions about the library > To: boost-users(a)lists.boost.org > > > > > > ? ?2. If my platform does not support HW floating point ops, and all my > > > ? ?sample values are, e.g. ints, is there a way to specify that the > > > *computation > > > ? ?*and *return value itself* (i.e. result_type, e.g. the mean) will be done > > > ? ?in ints (naturally, at the cost of precision)? > > > > I have used UDT as I needed some extra information from the results (as I was > working on data from a time series). The reverse, using a POD like int must be > possible. Instead of the first argument being float/double, use an int. If that > does not work, you can wrap an int in a UDT, implement some of the operators > like '=', '<', '/' depending on the accumulator you plan to use (I did that as I > needed to send a UDT). > > Using an int still returns a float -- which is quite sensible. You might be able to write a custom extractor which can return an int. I have not explored it. I always thought the type you give as input is the type that gets returned. > By UDT do you mean User Defined Type? > This is an interesting approach. > I didn't realize that the result_type depends on the value type in > that way, I didn't see any UDTs mentioned in the docs. Yes, I mean writing a class/struct. I had to overload '<', '>', '+=' and '/' and I use it for variance, mean, median, min, max and my implementation of percentile. Remember to specialize std::numeric_limits for the UDT you write. Else, the min and/or max will have values that you have not added in the accumulator (garbage values). I had a tough time debugging it and finding the solution. Also, on Windows, you need to derive your specialization from _Num_base. As for implementing a generic rolling type: 1. You need to store your values in a circular buffer. 2. Each time you add a value into the buffer, pass the contents to a pristine accumulator. This may be sub optimal but works. Especially for those calculations where it is not easy to remove the effect of the first data that you want to pop. I had to do it this way because I was dealing with time series. If I want a rolling computation for a 1 hour window, I might add 1 sample and may have to remove more than 1 sample to ensure first-last is 1 hour window in the buffer. -dhruva Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com

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[serialization] Uninitialized member in xml_archive_exception
by Gevorg Voskanyan 10 Aug '09

10 Aug '09

Hi, A coworker of mine has found an issue in boost::archive::xml_archive_exception - the constructor does not initialize the 'code' member. As the issue is not fixed in trunk yet, I went ahead and created the ticket #3331 to track it. Given the triviality of the fix, any chance it making into 1.40 ? Thanks, Gevorg

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how to Sort boost collection class using multi sorting options/criteria
by ch.asad＠gmail.com 10 Aug '09

10 Aug '09

Hi I am using boost collection class. I did sorting e.g apply a quick/bubble sort algo , but i want to do sorting using multiple criteria. how we can implement using boost. Do boost have any classes or functions through which I can easily sort the data using multiple options? Thanks. Asad -- View this message in context: http://www.nabble.com/how-to-Sort-boost-collection-class-using-multi-sortin… Sent from the Boost - Users mailing list archive at Nabble.com.

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How shared_from_this() work when it inherited from more than one time
by R. P. Janaka 10 Aug '09

10 Aug '09

please can anyone explain the reason for the following behavior #include <iostream> #include <boost/enable_shared_from_this.hpp> using namespace std; class A; typedef boost::shared_ptr<A> A_sptr_t; class B; typedef boost::shared_ptr<B> B_sptr_t; class A : public boost::enable_shared_from_this<A> { public: A() {} virtual ~A() {} }; class B : public A, public boost::enable_shared_from_this<B> { public: B() {} virtual ~B() {} void f(void) { cout << "this is working " << boost::enable_shared_from_this<B>::shared_from_this() << endl; } }; int main() { B_sptr_t b(new B()); b->f(); return 0; } the program will be terminated with the following message terminate called after throwing an instance of 'boost::bad_weak_ptr' what(): boost::bad_weak_ptr Aborted -- Regards, R. P. Janaka

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[Asio] io_service::work::reset()
by Robert Jones 10 Aug '09

10 Aug '09

boost version 1.39.0 The documentation on io_service includes an example of calling work.reset(), which is a pretty essential piece of functionality. The documentation page on io_service::work does not list reset() as a member function. Am I missing something? - Rob.

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[MultiIndex] how to reindex
by Igor R 10 Aug '09

10 Aug '09

Hello, Is it possible to rebuild container indices? I couldn't find any appropriate method in the docs, and even the "swap-trick" doesn't seem to work. The only way that worked so far was to rebuild the container from scratch...

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