April 2011 - Boost - lists.boost.org

[MSM] feature request stop(const event& event_)
by Richard Szabo 01 Apr '11

01 Apr '11

Hi Christophe and all Now I have to put some effort to residing out code using MSM because one of our module where we use MSM has reached it's limits and we won't be able to compile it any more with VC9 32 bit compiler. In our implementation we have several sub state machines (around 20 per main state machine instance at the moment) ( nested in 4 level deep) and over time as we extend the functionality we introduce new sub state machines which are covering new functionality ... We now can not add any more new sub state machines because we can not compile any more :(. So I have decided to split the big state machines with a lot of subs state machines to stand alone small state machine instances and use our dispatching framework to dispatch events between them. This way I will get small compile units. I'm managed to complete a job apart form one problem I have now. I'm not able to generally trigger the exit functions on the current active states of a state machine when it is finished it's execution like when a sub state machine exists to the outer state machine. Is it possible to implement something like stop method on the back end which would call exit on each region current state and than an exit of the state machine whit an event passed as an argument. ? this would help me a lot and it would be similar to the start. other minor thing is it possible to make public this version of start methode in the back_end ? template <class Event> void start(Event const& incomingEvent) Br. Richard

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Re: [boost] [submission] STL-compliant containers with copy-on-write
by Alexandr Sterligov 01 Apr '11

01 Apr '11

I'm working with embedded software and we have to use COW containers pretty often. I haven't found any COW container implementation which may replace STL containers and had to implemented it. It is not possible to make STL containers with COW keeping all semantics of the STL containers. For example, almost any member-function may throw, because copy ctor may throw. It is not always safe to replace std::vector with mine cow_vector, but in most cases it is safe. For example, it is not safe if you have saved constant pointer or constant reference from constant cow_vector. But with std::vector saving addresses is not a good idea as well, because resize, push_back and others may cause address change. In my implementation iterators are safe, for example: cow_vector<int> a; a.push_back( 1 ); cow_vector<int> b; b.push_back( 2 ); cow_vector<int>::const_iterator itA = a.begin(); assert( *itA == 1 ); cow_vector<int>::const_iterator itB = b.begin(); assert( *itB == 2 ); b = a; assert( itA == a.begin() ); assert( itB == b.begin() ); assert( *itA == 1 ); assert( *itB == 1 ); a[0] = 3; // or *a.begin() = 3 assert( itA == a.begin() ); assert( itB == b.begin() ); assert( *itA == 3 ); assert( *itB == 1 ); You example: int* p = &v[1]; // copying is done here v[0] = 1; assert( p == &v[1] ); // still valid as copying was done before. But in following case it won't work now: void test( const cow_vector<int>& a ) { const int *a = &v[1]; v[0] = 1; assert( p != &v[1] ); // sorry, another pointer if internal buffer was shared. } Please note, that it's possible to do copying if any reference or pointer is taken from iterator or container itself, but my current implementation doesn't do it. That's easy to change. > IMO it isn't possible to really make that work anyway since STL > containers expose references to their elements *and* make guarantees > about iterator stability and element layout. For example, if v is a > vector and I do > > v[0] = 1; > > it's not allowed to change the address of v[1] > -- > Dave Abrahams > BoostPro Computing > http://www.boostpro.com ---- Best regards, Alexander Sterligov

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GSOC2011 (Introduction)
by Harinderpal Singh 01 Apr '11

01 Apr '11

Hi My name is Harinderpal Singh. I am from Lovely Professional University, Punjab, India. I am a fourth year B.Tech student. I have worked on c++. I also have basic knowledge of Mysql. I have competed in various inter college level competitions. I work on linux(ubuntu) and also have knowledge of windows. I don't have any experience with open source previously.I am interested in Checks & Hashes module Regards Harinderpal Singh Website; http://www.iyouth.in Blog: http://codelinguist.wordpress.com/ <http://codelinguist.wordpress.com/> +91-9888573505

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