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  • Direct boost serialization to char array

    - by scooterman
    Hi all, Boost serialization doc's assert that the way to serialize/deserialize items is using a binary/text archive with a stream on the underlying structure. This works fine if I wan't to use the serialized data as an std::string, but my intention is to convert it directly to a char* buffer. How can I achieve this without creating a temporary string?

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  • C++ boost thread reusing threads

    - by aaa
    hi. I am trying to accomplish something like this: thread t; // create/initialize thread t.launch(); // launch thread. t.wait(); // wait t.launch(); // relaunch the same thread How to go about implementing something like this using boost threads? in essence, I need persistent relaunch-able thread. Thanks

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  • C++ boost wave, scoped macro

    - by aaa
    hello. Is it possible to have scoped macros using custom defined macros through boost wave? I know it should a possible with C++0x however I am working with regular C++. If it is possible, can you provide link or reference how to accomplish this? Thanks

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  • lambda vs. operator.attrGetter('xxx') as sort key in Python

    - by Paul McGuire
    I am looking at some code that has a lot of sort calls using comparison functions, and it seems like it should be using key functions. If you were to change seq.sort(lambda x,y: cmp(x.xxx, y.xxx)), which is preferable: seq.sort(key=operator.attrgetter('xxx')) or: seq.sort(key=lambda a:a.xxx) I would also be interested in comments on the merits of making changes to existing code that works.

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  • any stl/boost functors to call operator()

    - by Voivoid
    template <typename T> struct Foo { void operator()(T& t) { t(); } }; Is there any standart or boost functor with the similar implementation? I need it to iterate over container of functors: std::for_each(beginIter, endIter, Foo<Bar>()); Or maybe there are other way to do it?

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  • Mixing C and C++, raw pointers and (boost) shared pointers

    - by oompahloompah
    I am working in C++ with some legacy C code. I have a data structure that (during initialisation), makes a copy of the structure pointed to a ptr passed to its initialisation pointer. Here is a simplification of what I am trying to do - hopefully, no important detail has been lost in the "simplification": /* C code */ typedef struct MyData { double * elems; unsigned int len; }; int NEW_mydata(MyData* data, unsigned int len) { // no error checking data->elems = (double *)calloc(len, sizeof(double)); return 0; } typedef struct Foo { MyData data data_; }; void InitFoo(Foo * foo, const MyData * the_data) { //alloc mem etc ... then assign the STRUCTURE foo.data_ = *thedata ; } C++ code ------------- typedef boost::shared_ptr<MyData> MyDataPtr; typedef std::map<std::string, MyDataPtr> Datamap; class FooWrapper { public: FooWrapper(const std::string& key) { MyDataPtr mdp = dmap[key]; InitFoo(&m_foo, const_cast<MyData*>((*mdp.get()))); } ~FooWrapper(); double get_element(unsigned int index ) const { return m_foo.elems[index]; } private: // non copyable, non-assignable FooWrapper(const FooWrapper&); FooWrapper& operator= (const FooWrapper&); Foo m_foo; }; int main(int argc, char *argv[]) { MyData data1, data2; Datamap dmap; NEW_mydata(&data1, 10); data1->elems[0] = static_cast<double>(22/7); NEW_mydata(&data2, 42); data2->elems[0] = static_cast<double>(13/21); boost::shared_ptr d1(&data1), d2(&data2); dmap["data1"] = d1; dmap["data2"] = d2; FooWrapper fw("data1"); //expect 22/7, get something else (random number?) double ret fw.get_element(0); } Essentially, what I want to know is this: Is there any reason why the data retrieved from the map is different from the one stored in the map?

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  • lambda vs. operator.attrgetter('xxx') as sort key function in Python

    - by Paul McGuire
    I am looking at some code that has a lot of sort calls using comparison functions, and it seems like it should be using key functions. If you were to change seq.sort(lambda x,y: cmp(x.xxx, y.xxx)), which is preferable: seq.sort(key=operator.attrgetter('xxx')) or: seq.sort(key=lambda a:a.xxx) I would also be interested in comments on the merits of making changes to existing code that works.

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  • Boost::asio::endpoint::size() and resize()

    - by p00ya
    hi. I was reading the boost endpoint documentation and saw size() and resize() member funcs. the documentation says: Gets the underlying size of the endpoint in the native type. what does this size represent and where can it be used/resized ? thanks.

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  • Custom InputIterator for Boost graph (BGL)

    - by Shadow
    Hi, I have a graph with custom properties to the vertices and edges. I now want to create a copy of this graph, but I don't want the vertices to be as complex as in the original. By this I mean that it would suffice that the vertices have the same indices (vertex_index_t) as they do in the original graph. Instead of doing the copying by hand I wanted to use the copy-functionality of boost::adjacency_list (s. http://www.boost.org/doc/libs/1_37_0/libs/graph/doc/adjacency_list.html): template <class EdgeIterator> adjacency_list(EdgeIterator first, EdgeIterator last, vertices_size_type n, edges_size_type m = 0, const GraphProperty& p = GraphProperty()) The description there says: The EdgeIterator must be a model of InputIterator. The value type of the EdgeIterator must be a std::pair, where the type in the pair is an integer type. The integers will correspond to vertices, and they must all fall in the range of [0, n). Unfortunately I have to admit that I don't quite get it how to define an EdgeIterator that is a model of InputIterator. Here's what I've succeded so far: template< class EdgeIterator, class Edge > class MyEdgeIterator// : public input_iterator< std::pair<int, int> > { public: MyEdgeIterator() {}; MyEdgeIterator(EdgeIterator& rhs) : actual_edge_it_(rhs) {}; MyEdgeIterator(const MyEdgeIterator& to_copy) {}; bool operator==(const MyEdgeIterator& to_compare) { return actual_edge_it_ == to_compare.actual_edge_it_; } bool operator!=(const MyEdgeIterator& to_compare) { return !(*this == to_compare); } Edge operator*() const { return *actual_edge_it_; } const MyEdgeIterator* operator->() const; MyEdgeIterator& operator ++() { ++actual_edge_it_; return *this; } MyEdgeIterator operator ++(int) { MyEdgeIterator<EdgeIterator, Edge> tmp = *this; ++*this; return tmp; } private: EdgeIterator& actual_edge_it_; } However, this doesn't work as it is supposed to and I ran out of clues. So, how do I define the appropriate InputIterator?

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  • RadioButtons and Lambda Expressions

    - by MightyZot
    Radio buttons operate in groups. They are used to present mutually exclusive lists of options. Since I started programming in Windows 20 years ago, I have always been frustrated about how they are implemented. To make them operate as a group, you put your radio buttons in a group box. Conversely, to group radio buttons in HTML, you simply give them all the same name. Radio buttons with the same name or ID in HTML operate as one mutually exclusive group of options. In C#, all your radio buttons must have unique names and you use group boxes to group them. I’m in the process of converting some old code to C# and I’m tasked with creating a user control with groups of radio buttons on it. I started out writing the traditional switch…case statements to check the appropriate radio button based upon value, loops to uncheck them all, etc. Then it occurred to me that I could stick the radio buttons in a Dictionary or List and use Lambda expressions to make my code a lot more maintainable. So, here is what I ended up with: Here is a dictionary that contains my list of radio buttons and their values. I used their values as the keys, so that I can select them by value. Now, instead of using loops and switch…case statements to control the radio buttons, I use the lambda syntax and extension methods. Selecting a Radio Button by Value This code is inside of a property accessor, so “value” represents the value passed into the property accessor. The “First” extension method uses the delegate represented by the lambda expression to select the radio button (actually KeyValuePair) that represents the passed in value. Finally, the resulting checkbox is checked. Since the radio buttons are in the same group, they function as a group, the appropriate radio button is selected while the others are unselected. Reading the Value This is the get accessor for the property that returns the value of the checked radio button. Now, if you’re using binding, this code is likely not necessary; however, I didn’t want to use binding in this case, so I think this is a good alternative to the traditional loops and switch…case statements.

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  • What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

    - by Maciek Kreft
    package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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  • How to pass user-defined structs using boost mpi

    - by lava
    I am trying to send a user-defined structure named ABC using boost::mpi::send () call. The given struct contains a vector "data" whose size is determined at runtime. Objects of struct ABC are sent by master to slaves. But the slaves need to know the size of vector "data" so that the sufficient buffer is available on the slave to receive this data. I can work around it by sending the size first and initialize sufficient buffer on the slave before receiving the objects of struct ABC. But that defeats the whole purpose of using STL containers. Does anyone know of a better way to do handle this ? Any suggestions are greatly appreciated. Here is a sample code that describes the intent of my program. This code fails at runtime due to above mentioned reason. struct ABC { double cur_stock_price; double strike_price; double risk_free_rate; double option_price; std::vector <char> data; }; namespace boost { namespace serialization { template<class Archive> void serialize (Archive &ar, struct ABC &abc, unsigned int version) { ar & abc.cur_stock_price; ar & abc.strike_price; ar & abc.risk_free_rate; ar & abc.option_price; ar & bopr.data; } } } BOOST_IS_MPI_DATATYPE (ABC); int main(int argc, char* argv[]) { mpi::environment env (argc, argv); mpi::communicator world; if (world.rank () == 0) { ABC abc_obj; abc.cur_stock_price = 1.0; abc.strike_price = 5.0; abc.risk_free_rate = 2.5; abc.option_price = 3.0; abc_obj.data.push_back ('a'); abc_obj.data.push_back ('b'); world.send ( 1, ANY_TAG, abc_obj;); std::cout << "Rank 0 OK!" << std::endl; } else if (world.rank () == 1) { ABC abc_obj; // Fails here because abc_obj is not big enough world.recv (0,ANY_TAG, abc_obj;); std::cout << "Rank 1 OK!" << std::endl; for (int i = 0; i < abc_obj;.data.size(); i++) std::cout << i << "=" << abc_obj.data[i] << std::endl; } MPI_Finalize(); return 0; }

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  • How to implement tokenizer.rbegin() and rend() for boost::tokenizer ?

    - by Chan
    Hello everyone, I'm playing around with boost::tokenizer however I realize that it does not support rbegin() and rend(). I would like to ask how can I add these two functions to the existing class? This is from the boost site: #include <iostream> #include <string> #include <boost/tokenizer.hpp> using namespace std; using namespace boost; int main() { string str( "12/12/1986" ); typedef boost::tokenizer<boost::char_separator<char>> tokenizer; boost::char_separator<char> sep( "/" ); tokenizer tokens( str, sep ); cout << *tokens.begin() << endl; // cout << *tokens.rbegin() << endl; How could I implement this? return 0; }

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  • How to properly translate the "var" result of a lambda expression to a concrete type?

    - by CrimsonX
    So I'm trying to learn more about lambda expressions. I read this question on stackoverflow, concurred with the chosen answer, and have attempted to implement the algorithm using a console app in C# using a simple LINQ expression. My question is: how do I translate the "var result" of the lambda expression into a usable object that I can then print the result? I would also appreciate an in-depth explanation of what is happening when I declare the outer => outer.Value.Frequency (I've read numerous explanations of lambda expressions but additional clarification would help) C# //Input : {5, 13, 6, 5, 13, 7, 8, 6, 5} //Output : {5, 5, 5, 13, 13, 6, 6, 7, 8} //The question is to arrange the numbers in the array in decreasing order of their frequency, preserving the order of their occurrence. //If there is a tie, like in this example between 13 and 6, then the number occurring first in the input array would come first in the output array. List<int> input = new List<int>(); input.Add(5); input.Add(13); input.Add(6); input.Add(5); input.Add(13); input.Add(7); input.Add(8); input.Add(6); input.Add(5); Dictionary<int, FrequencyAndValue> dictionary = new Dictionary<int, FrequencyAndValue>(); foreach (int number in input) { if (!dictionary.ContainsKey(number)) { dictionary.Add(number, new FrequencyAndValue(1, number) ); } else { dictionary[number].Frequency++; } } var result = dictionary.OrderByDescending(outer => outer.Value.Frequency); // How to translate the result into something I can print??

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  • boost spirit semantic action parameters

    - by lurscher
    Hi, in this article about boost spirit semantic actions it is mentioned that There are actually 2 more arguments being passed: the parser context and a reference to a boolean ‘hit’ parameter. The parser context is meaningful only if the semantic action is attached somewhere to the right hand side of a rule. We will see more information about this shortly. The boolean value can be set to false inside the semantic action invalidates the match in retrospective, making the parser fail. All fine, but i've been trying to find an example passing a function object as semantic action that uses the other parameters (parser context and hit boolean) but i haven't found any. I would love to see an example using regular functions or function objects, as i barely can grok the phoenix voodoo

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  • Pass by reference in Boost::Python

    - by Fabzter
    Hi everybody. Consider something like: struct Parameter { int a; Parameter(){a = 0} void setA(int newA){a = newA;} }; struct MyClass { void changeParameter(Parameter &p){ p.setA(-1);} }; Well, let's fast forward, and imagine I already wrapped those classes, exposing everything to python, and imagine also I instantiate an object of Parameter in the C++ code, which I pass to the python script, and that python script uses a MyClass object to modify the instance of Parameter I created at the beginning in the C++ code. After that code executes, in C++ Parameter instance is unchanged!!! This means it was passed by value (or something alike :S), not by reference. But I thought I declared it to be passed by reference... I can't seem to find Boost::Python documentation about passing by reference (although there seems to be enough doc about returning by reference...). Can anyone give some hint or pointer please?

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  • Boost bind function

    - by Gokul
    Hi, I have a abstract base class A and a set of 10 derived classes. The infix operator is overloaded in all of the derived classes class A{ void printNode( std::ostream& os ) { this->printNode_p(); } void printNode_p( std::ostream& os ) { os << (*this); } }; There is a container which stores the base class pointers. I want to use boost::bind function to call the overloaded infix operator in each of its derived class. I have written like this std::vector<A*> m_args .... std::ostream os; for_each( m_args.begin(), m_args.end(), bind(&A::printNode, _1, os) ); What is the problem with this code? Thanks, Gokul.

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  • Boost.Program_Options not working with short options

    - by inajamaica
    I have the following options_description: po::options_description config("Configuration File or Command Line"); config.add_options() ("run-time,t", po::value(&runTime_)-default_value(1440.0), "set max simulation duration") ("starting-iteration,i", po::value(&startingIteration_)-default_value(1), "set starting simulation iteration") ("repetitions,r", po::value(&repetitions_)-default_value(100), "set number of iterations") ... ; As you can see the three shown have a long,short names employed. The long versions all work. However, none of the short ones do, and each time I try a -t 12345.0 or a -i 12345, etc., I get the following from Program_Options: std::logic_error: in option 'starting-iteration': invalid option value I'm using Boost 1.42 on Win32. Any thoughts on what might be going on here? Thanks!

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  • Using STL/Boost to initialize a hard-coded set<vector<int> >

    - by Hooked
    Like this question already asked, I'd like to initialize a container using STL where the elements are hard-coded in the cleanest manner possible. In this case, the elements are a doubly nested container: set<vector<int> > A; And I'd like (for example) to put the following values in: A = [[0,0,1],[0,1,0],[1,0,0],[0,0,0]]; C++0x fine, using g++ 4.4.1. STL is preferable as I don't use Boost for any other parts of the code (though I wouldn't mind an example with it!).

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  • pushing back an boost::ptr_vector<...>::iterator in another boost::ptr_vector?

    - by Ethan Nash
    Hi all, I have the following code (just typed it in here, might have typos or stuff): typedef boost::ptr_vector<SomeClass> tvec; tvec v; // ... fill v ... tvec vsnap; for(tvec::iterator it = v.begin(); it != v.end(); ++it) { if((*v).anyCondition) vsnap.push_back( it ); // (*it) or &(*it) doesn't work } My problem is now that i cant push_back an iterator in any way, I just don't get the pointer out of the iterator. Is there an easy way i didnt see, or are boosts ptr_vector the false choice for this case? Thanks in advance.

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