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  • Can you dynamically combine multiple conditional functions into one in Python?

    - by erich
    I'm curious if it's possible to take several conditional functions and create one function that checks them all (e.g. the way a generator takes a procedure for iterating through a series and creates an iterator). The basic usage case would be when you have a large number of conditional parameters (e.g. "max_a", "min_a", "max_b", "min_b", etc.), many of which could be blank. They would all be passed to this "function creating" function, which would then return one function that checked them all. Below is an example of a naive way of doing what I'm asking: def combining_function(max_a, min_a, max_b, min_b, ...): f_array = [] if max_a is not None: f_array.append( lambda x: x.a < max_a ) if min_a is not None: f_array.append( lambda x: x.a > min_a ) ... return lambda x: all( [ f(x) for f in f_array ] ) What I'm wondering is what is the most efficient to achieve what's being done above? It seems like executing a function call for every function in f_array would create a decent amount of overhead, but perhaps I'm engaging in premature/unnecessary optimization. Regardless, I'd be interested to see if anyone else has come across usage cases like this and how they proceeded. Also, if this isn't possible in Python, is it possible in other (perhaps more functional) languages?

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  • std::vector elements initializing

    - by Chameleon
    std::vector<int> v1(1000); std::vector<std::vector<int>> v2(1000); std::vector<std::vector<int>::const_iterator> v3(1000); How elements of these 3 vectors initialized? About int, I test it and I saw that all elements become 0. Is this standard? I believed that primitives remain undefined. I create a vector with 300000000 elements, give non-zero values, delete it and recreate it, to avoid OS memory clear for data safety. Elements of recreated vector were 0 too. What about iterator? Is there a initial value (0) for default constructor or initial value remains undefined? When I check this, iterators point to 0, but this can be OS When I create a special object to track constructors, I saw that for first object, vector run the default constructor and for all others it run the copy constructor. Is this standard? Is there a way to completely avoid initialization of elements? Or I must create my own vector? (Oh my God, I always say NOT ANOTHER VECTOR IMPLEMENTATION) I ask because I use ultra huge sparse matrices with parallel processing, so I cannot use push_back() and of course I don't want useless initialization, when later I will change the value.

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  • crash when using stl vector at instead of operator[]

    - by Jamie Cook
    I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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  • How to load/save C++ class instance (using STL containers) to disk

    - by supert
    I have a C++ class representing a hierarchically organised data tree which is very large (~Gb, basically as large as I can get away with in memory). It uses an STL list to store information at each node plus iterators to other nodes. Each node has only one parent, but 0-10 children. Abstracted, it looks something like: struct node { public: node_list_iterator parent; // iterator to a single parent node double node_data_array[X]; map<int,node_list_iterator> children; // iterators to child nodes }; class strategy { private: list<node> tree; // hierarchically linked list of nodes struct some_other_data; public: void build(); // build the tree void save(); // save the tree from disk void load(); // load the tree from disk void use(); // use the tree }; I would like to implement the load() and save() to disk, and it should be fairly fast, however the obvious problems are: I don't know the size in advance; The data contains iterators, which are volatile; My ignorance of C++ is prodigious. Could anyone suggest a pure C++ solution please?

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  • C++ STL: How to iterate vector while requiring access to element and its index?

    - by Ashwin
    I frequently find myself requiring to iterate over STL vectors. While I am doing this I require access to both the vector element and its index. I used to do this as: typedef std::vector<Foo> FooVec; typedef FooVec::iterator FooVecIter; FooVec fooVec; int index = 0; for (FooVecIter i = fooVec.begin(); i != fooVec.end(); ++i, ++index) { Foo& foo = *i; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } After discovering BOOST_FOREACH, I shortened this to: typedef std::vector<Foo> FooVec; FooVec fooVec; int index = -1; BOOST_FOREACH( Foo& foo, fooVec ) { ++index; if (foo.somethingIsTrue()) // True for most elements std::cout << index << ": " << foo << std::endl; } Is there a better or more elegant way to iterate over STL vectors when both reference to the vector element and its index is required? I am aware of the alternative: for (int i = 0; i < fooVec.size(); ++i) But I keep reading about how it is not a good practice to iterate over STL containers like this.

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  • How to check if a position inside a std string exists ?? (c++)

    - by yox
    Hello, i have a long string variable and i want to search in it for specific words and limit text according to thoses words. Say i have the following text : "This amazing new wearable audio solution features a working speaker embedded into the front of the shirt and can play music or sound effects appropriate for any situation. It's just like starring in your own movie" and the words : "solution" , "movie". I want to substract from the big string (like google in results page): "...new wearable audio solution features a working speaker embedded..." and "...just like starring in your own movie" for that i'm using the code : for (std::vector<string>::iterator it = words.begin(); it != words.end(); ++it) { int loc1 = (int)desc.find( *it, 0 ); if( loc1 != string::npos ) { while(desc.at(loc1-i) && i<=80){ i++; from=loc1-i; if(i==80) fromdots=true; } i=0; while(desc.at(loc1+(int)(*it).size()+i) && i<=80){ i++; to=loc1+(int)(*it).size()+i; if(i==80) todots=true; } for(int i=from;i<=to;i++){ if(fromdots) mini+="..."; mini+=desc.at(i); if(todots) mini+="..."; } } but desc.at(loc1-i) causes OutOfRange exception... I don't know how to check if that position exists without causing an exception ! Help please!

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  • Syntax for finding structs in multisets - C++

    - by Sarah
    I can't seem to figure out the syntax for finding structs in containers. I have a multiset of Event structs. I'm trying to find one of these structs by searching on its key. I get the compiler error commented below. struct Event { public: bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } bool operator > ( const Event & rhs ) const { return ( time > rhs.time ); } bool operator == ( const Event & rhs ) const { return ( time == rhs.time ); } double time; int eventID; int hostID; int s; }; typedef std::multiset< Event, std::less< Event > > EventPQ; EventPQ currentEvents; double oldRecTime = 20.0; EventPQ::iterator ceItr = currentEvents.find( EventPQ::key_type( oldRecTime ) ); // no matching function call I've tried a few permutations to no avail. I thought defining the conditional equality operator was going to be enough.

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  • Does operator precedence in C++ differ for pointers and iterators?

    - by oraz
    The code below demonstrates this difference: #include <iostream> #include <string> int main() { char s[] = "ABCD"; std::string str(s); char *p = s; while(*p) { *p++ = tolower(*p); // <-- incr after assignment } std::cout << s << std::endl; std::string::iterator it = str.begin(), end = str.end(); while(it != end) { *it++ = tolower(*it); // <-- incr before assignment ? } std::cout << str << std::endl; return 0; } the code above outputs: abcd bcd if we separate assignment operation and increment operator: while(it != end) { *it = tolower(*it); // <-- incr before assignment ? it++; } the output will be as expected. What's wrong with the original code? $ g++ --version g++ (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) Copyright (C) 2004 Free Software Foundation, Inc.

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  • Apache POI rows number

    - by sys_debug
    I am using Apache POI java and want to get the total number of rows which are not empty. I successfully processed a whole row with all its columns. Now I am assuming that I get an excel sheet with multiple rows and not a single row...so how to go about that? I was thinking of getting total number of rows (int n) and then loop until i<=n but not sure. Suggestions are most welcome :) Note: Apache POI version is 3.8. I am not dealing with Xlsx format...only xls. Yes I tried this code but got 20 in return....which is not possible given I have only 5 rows FileInputStream fileInputStream = new FileInputStream("COD.xls"); HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream); HSSFSheet worksheet = workbook.getSheet("COD"); HSSFRow row1 = worksheet.getRow(3); Iterator rows = worksheet.rowIterator(); int noOfRows = 0; while( rows.hasNext() ) { HSSFRow row = (HSSFRow) rows.next(); noOfRows++; } System.out.println("Number of Rows: " + noOfRows);

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  • C++ bughunt - High-score insertion in a vector crashes the program

    - by Francisco P.
    Hello, everyone! I have a game I'm working on. My players are stored in a vector, and, at the end of the game, the game crashes when trying to insert the high-scores in the correct positions. Here's what I have (please ignore the portuguese comments, the code is pretty straightforward :P): //TOTAL_HIGHSCORES is the max. number of hiscores that i'm willing to store. This is set as 10. bool Game::updateHiScores() { bool stopIterating; bool scoresChanged = false; //Se ainda nao existirem TOTAL_HISCORES melhores pontuacoes ou se a pontuacao for melhor que uma das existentes for (size_t i = 0; i < players.size(); ++i) { //&& !(players[i].isAI()) if (players[i].getScoreValue() > 0 && (hiScores.size() < TOTAL_HISCORES || hiScores.back() < players[i].getScore())) { scoresChanged = true; if(hiScores.empty() || hiScores.back() >= players[i].getScore()) hiScores.push_back(players[i].getScore()); else { //Ciclo que encontra e insere a pontuacao no lugar desejado stopIterating = false; for(vector<Score>::iterator it = hiScores.begin(); it < hiScores.end() && !(stopIterating); ++it) { if(*it <= players[i].getScore()) { //E inserida na posicao 'it' o Score correspondente hiScores.insert(it, players[i].getScore()); //Verifica se o comprimento do vector esta dentro do desejado, se nao estiver, este e rectificado if (hiScores.size() > TOTAL_HISCORES) hiScores.pop_back(); stopIterating = true; } } } } } if (scoresChanged) sort(hiScores.begin(), hiScores.end(), higher); return scoresChanged; } What am I doing wrong here? Thanks for your time, fellas.

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  • How to call shared_ptr<boost::signal> from a vector in a loop?

    - by BTR
    I've got a working callback system that uses boost::signal. I'm extending it into a more flexible and efficient callback manager which uses a vector of shared_ptr's to my signals. I've been able to successfully create and add callbacks to the list, but I'm unclear as to how to actually execute the signals. ... // Signal aliases typedef boost::signal<void (float *, int32_t)> Callback; typedef std::shared_ptr<Callback> CallbackRef; // The callback list std::vector<CallbackRef> mCallbacks; // Adds a callback to the list template<typename T> void addCallback(void (T::* callbackFunction)(float * data, int32_t size), T * callbackObject) { CallbackRef mCallback = CallbackRef(new Callback()); mCallback->connect(boost::function<void (float *, int32_t)>(boost::bind(callbackFunction, callbackObject, _1, _2))); mCallbacks.push_back(mCallback); } // Pass the float array and its size to the callbacks void execute(float * data, int32_t size) { // Iterate through the callback list for (vector<CallbackRef>::iterator i = mCallbacks.begin(); i != mCallbacks.end(); ++i) { // What do I do here? // (* i)(data, size); // <-- Dereferencing doesn't work } } ... All of this code works. I'm just not sure how to run the call from within a shared_ptr from with a vector. Any help would be neat-o. Thanks, in advance.

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  • need help with C++ using maps to keep track of words in a INPUT file

    - by eNetik
    Let say i have a text file with today is today but tomorrow is today tomorrow then using maps how can i keep track of the words that are repeated? and on which line it repeats? so far i have each string in the file read in as a temp and it is stored in the following way: map<string,int> storage; int count = 1 // for the first line of the file if(infile.is_open()){ while( !infile.eof() ){ getline(in, line); istringstream my_string(line); while(my_string.good()){ string temp; my_string >> temp; storage[temp] = count } count++;// so that every string read in the next line will be recorded as that line. } } map<string,int>::iterator m; for(int m = storage.begin(); m!= storage.end(); m++){ out<<m->first<<": "<<"line "<<m->second<<endl; } right now the output is just but: line 1 is: line 2 today: line 2 tomorrow: line 2 But instead.. it should print out(no repeating strings): today : line 1 occurred 2 times, line 2 occurred 1 time. is: line 1 occurred 1 time, line 2 occurred 1 time. but: line 1 occurred 1 time. tomorrow: line 2 occurred 2 times. Note: the order of the string does not matter. Any help would be appreciated. Thanks.

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  • C++ map performance - Linux (30 sec) vs Windows (30 mins) !!!

    - by sonofdelphi
    I need to process a list of files. The processing action should not be repeated for the same file. The code I am using for this is - using namespace std; vector<File*> gInputFileList; //Can contain duplicates, File has member sFilename map<string, File*> gProcessedFileList; //Using map to avoid linear search costs void processFile(File* pFile) { File* pProcessedFile = gProcessedFileList[pFile->sFilename]; if(pProcessedFile != NULL) return; //Already processed foo(pFile); //foo() is the action to do for each file gProcessedFileList[pFile->sFilename] = pFile; } void main() { size_t n= gInputFileList.size(); //Using array syntax (iterator syntax also gives identical performance) for(size_t i=0; i<n; i++){ processFile(gInputFileList[i]); } } The code works correctly, but... My problem is that when the input size is 1000, it takes 30 minutes - HALF AN HOUR - on Windows/Visual Studio 2008 Express (both Debug and Release builds). For the same input, it takes only 40 seconds to run on Linux/gcc! What could be the problem? The action foo() takes only a very short time to execute, when used separately. Should I be using something like vector::reserve for the map?

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  • servlet and jsp sending query result following MVC framework

    - by kawtousse
    Hi every one, in order to separate java code and html code and be more faithful to MVC framework i am coding like that; in the servlet i put the following: net.sf.hibernate.Session s = null; net.sf.hibernate.Transaction tx; try { s= HibernateUtil.currentSession(); tx=s.beginTransaction(); Query query = s.createQuery("select opcemployees.Nom,opcemployees.Prenom,dailytimesheet.TrackingDate,dailytimesheet.Activity," + "dailytimesheet.ProjectCode,dailytimesheet.WAName,dailytimesheet.TaskCode," + "dailytimesheet.TimeSpent,dailytimesheet.PercentTaskComplete from Opcemployees opcemployees,Dailytimesheet dailytimesheet " + "where opcemployees.Matricule=dailytimesheet.Matricule and dailytimesheet.Etat=3 " + "group by opcemployees.Nom,opcemployees.Prenom" ); for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()){ Object[] row = (Object[]) it.next(); request.setAttribute("items", row); }} } catch (HibernateException e){ e.printStackTrace(); } request.getRequestDispatcher("EspaceValidation.jsp").forward(request, response); and in jsp i start like that: <table> <c:forEach items="${items}" var="item"> <tr> <td>? </td> <td>?</td> </tr> </c:forEach> in this case what should i put exactly to obtain my result.a table fulled with the right value from the request

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  • STLifying C++ classes

    - by shambulator
    I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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  • an error "has no member named"

    - by helloWorld
    I have this snippet of the code account.cpp #include "account.h" #include <iostream> #include <string> using namespace std; Account::Account(string firstName, string lastName, int id) : strFirstName(firstName), strLastName(lastName), nID(id) {} void Account::printAccount(){ cout << strFirstName; } account.h #include <string> using std::string; class Account{ private: string strLastName; //Client's last name string strFirstName; //Client's first name int nID; //Client's ID number int nLines; //Number of lines related to account double lastBill; public: Account(string firstName, string lastName, int id); void printAccount(); }; company.h #ifndef CELLULAR_COMPANY_H #define CELLULAR_COMPANY_H #include <string> #include <list> #include <iostream> #include "account.h" using namespace std; class Company { private: list<Account> listOfAccounts; public: void addAccount(string firstName, string lastName, int id) { Account newAccount(firstName, lastName, id); listOfAccounts.push_back(newAccount); } void printAccounts(){ for(list<Account>::iterator i = listOfAccounts.begin(); i != listOfAccounts.end(); ++i){ i.printAccount; //here bug } } }; #endif // CELLULAR_COMPANY_H main.cpp #include "cellularcompany.h" int main(){ Company newCompany; newCompany.addAccount("Pavel", "Nedved", 11111); newCompany.printAccounts(); return 0; } can somebody please explain what does my error mean? thanks in advance (I have it in company.h see comment there) I have bug 'struct std::_List_iterator<Account>' has no member named 'printAccount'

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  • Returning a lua table on SWIG call

    - by Tom J Nowell
    I have a class with a methodcalled GetEnemiesLua. I have bound this class to lua using SWIG, and I can call this method using my lua code. I am trying to get the method to return a lua table of objects. Here is my current code: void CSpringGame::GetEnemiesLua(){ std::vector<springai::Unit*> enemies = callback->GetEnemyUnits(); if( enemies.empty()){ lua_pushnil(ai->L); return; } else{ lua_newtable(ai->L); int top = lua_gettop(ai->L); int index = 1; for (std::vector<springai::Unit*>::iterator it = enemies.begin(); it != enemies.end(); ++it) { //key lua_pushinteger(ai->L,index);//lua_pushstring(L, key); //value CSpringUnit* unit = new CSpringUnit(callback,*it,this); ai->PushIUnit(unit); lua_settable(ai->L, -3); ++index; } ::lua_pushvalue(ai->L,-1); } } PushIUnit is as follows: void CTestAI::PushIUnit(IUnit* unit){ SWIG_NewPointerObj(L,unit,SWIGTYPE_p_IUnit,1); } To test this I have the following code: t = game:GetEnemiesLua() if t == nil then game:SendToConsole("t is nil! ") end The result is always 't is nil', despite this being incorrect. I have put breakpoints in the code and it is indeed going over the loop, rather than doing lua_pushnil. So how do I make my method return a table when called via lua?

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  • Difference between these two functions that find Palindromes....

    - by Moin
    I wrote a function to check whether a word is palindrome or not but "unexpectedly", that function failed quite badly, here it is: bool isPalindrome (const string& s){ string reverse = ""; string original = s; for (string_sz i = 0; i != original.size(); ++i){ reverse += original.back(); original.pop_back(); } if (reverse == original) return true; else return false; } It gives me "string iterator offset out of range error" when you pass in a string with only one character and returns true even if we pass in an empty string (although I know its because of the intialisation of the reverse variable) and also when you pass in an unassigned string for example: string input; isPalindrome(input); Later, I found a better function which works as you would expect: bool found(const string& s) { bool found = true; for (string::const_iterator i = s.begin(), j = s.end() - 1; i < j; ++i, --j) { if (*i != *j) found = false; } return found; } Unlike the first function, this function correctly fails when you give it an unassigned string variable or an empty string and works for single characters and such... So, good people of stackoverflow please point out to me why the first function is so bad... Thank You.

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  • Bizarre C++ compiler problem

    - by Yassin
    Hi, I have the following C++ code: typedef istream_iterator<string> isi; // (1) vector<string> lineas(isi(cin), isi()); // (2) //vector<string> lineas; //copy(isi(cin), isi(), back_inserter(lineas)); typedef vector<string>::iterator vci; for (vci it = lineas.begin(); it != lineas.end(); ++it) cout &lt;&lt; *it &lt;&lt; endl; However, I get the error while compiling: test.cpp: In function 'int main(int, char**)': test.cpp:16: error: request for member 'begin' in 'lineas', which is of non-class type 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >(main(int, char**)::isi, main(int, char**)::isi (*)())' test.cpp:16: error: request for member 'end' in 'lineas', which is of non-class type 'std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >(main(int, char**)::isi, main(int, char**)::isi (*)())' However, if I replace (1) by (2), it compiles. I'm using g++ 4.4.0 What's wrong?

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  • C++ Segmentation Fault when Iterating through a Vector

    - by user1790374
    I have a program that maintains an integer vector. I have three functions that add an integer, remove an integer and check whether an integer is already in the vector. The problem is with the last one. vector<int> children; void CtpTestingApplication::addChild(int child) { for (int i=0; i<children.size(); i++) { //already a child if (children[i]==child) return; } //child not yet recorded children.push_back(child); received.push_back(false); cout<<"added child "<<child; } void CtpTestingApplication::removeChild(int child) { Enter_Method("removeChild"); for (int i=0; i<children.size(); i++) { //already a child, remove it if (children[i]==child) { children.erase(children.begin()+i); received.erase(received.begin()+i); cout<<"removed child "<<child; } } //not recorded, no need to remove } bool CtpTestingApplication::isChild(int child) { Enter_Method("isChild"); vector<int>::iterator ic; bool result = false; for (ic= children.begin(); ic < children.end(); ic++) { cout<<*ic<<" vs "<<child; // if (child==*ic) result = true; } return result; } I always get segmentation fault when I uncomment "if (child==*ic)", even though printouts show that the vector is not empty and contains the expected integers. For example, with the if statements commented, I can see 1 vs 4, 2 vs 4, 4 vs 4, 12 vs 4 I also attempted looping using children[i] and so on, but to no avail. Any help would be appreciated. Thank you.

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  • How can I avoid garbage collection delays in Java games? (Best Practices)

    - by Brian
    I'm performance tuning interactive games in Java for the Android platform. Once in a while there is a hiccup in drawing and interaction for garbage collection. Usually it's less than one tenth of a second, but sometimes it can be as large as 200ms on very slow devices. I am using the ddms profiler (part of the Android SDK) to search out where my memory allocations come from and excise them from my inner drawing and logic loops. The worst offender had been short loops done like, for(GameObject gob : interactiveObjects) gob.onDraw(canvas); where every single time the loop was executed there was an iterator allocated. I'm using arrays (ArrayList) for my objects now. If I ever want trees or hashes in an inner loop I know that I need to be careful or even reimplement them instead of using the Java Collections framework since I can't afford the extra garbage collection. That may come up when I'm looking at priority queues. I also have trouble where I want to display scores and progress using Canvas.drawText. This is bad, canvas.drawText("Your score is: " + Score.points, x, y, paint); because Strings, char arrays and StringBuffers will be allocated all over to make it work. If you have a few text display items and run the frame 60 times a second that begins to add up and will increase your garbage collection hiccups. I think the best choice here is to keep char[] arrays and decode your int or double manually into it and concatenate strings onto the beginning and end. I'd like to hear if there's something cleaner. I know there must be others out there dealing with this. How do you handle it and what are the pitfalls and best practices you've discovered to run interactively on Java or Android? These gc issues are enough to make me miss manual memory management, but not very much.

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  • for loop vs std::for_each with lambda

    - by Andrey
    Let's consider a template function written in C++11 which iterates over a container. Please exclude from consideration the range loop syntax because it is not yet supported by the compiler I'm working with. template <typename Container> void DoSomething(const Container& i_container) { // Option #1 for (auto it = std::begin(i_container); it != std::end(i_container); ++it) { // do something with *it } // Option #2 std::for_each(std::begin(i_container), std::end(i_container), [] (typename Container::const_reference element) { // do something with element }); } What are pros/cons of for loop vs std::for_each in terms of: a) performance? (I don't expect any difference) b) readability and maintainability? Here I see many disadvantages of for_each. It wouldn't accept a c-style array while the loop would. The declaration of the lambda formal parameter is so verbose, not possible to use auto there. It is not possible to break out of for_each. In pre- C++11 days arguments against for were a need of specifying the type for the iterator (doesn't hold any more) and an easy possibility of mistyping the loop condition (I've never done such mistake in 10 years). As a conclusion, my thoughts about for_each contradict the common opinion. What am I missing here?

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  • Including typedef of child in parent class

    - by Baz
    I have a class which looks something like this. I'd prefer to have the typedef of ParentMember in the Parent class and rename it Member. How might this be possible? The only way I can see is to have std::vector as a public member instead of using inheritance. typedef std::pair<std::string, boost::any> ParentMember; class Parent: public std::vector<ParentMember> { public: template <typename T> std::vector<T>& getMember(std::string& s) { MemberFinder finder(s); std::vector<ParentMember>::iterator member = std::find_if(begin(), end(), finder); boost::any& container = member->second; return boost::any_cast<std::vector<T>&>(container); } private: class Finder { ... }; };

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  • Why can't my vector access the variables in my nested structs?

    - by chucknorris
    #include<iostream> #include<vector> #include<string> #include<list> using namespace std; struct record{ int id; string fName; }; struct cells{ list<record> rec; }; vector<cells> hp; int main() { **hp.front().rec.front().fName = "jon"; return 0; } I have 2 structs. The first struct, struct record, is composed of 2 regular variables. In struct 2, I have a linked list of type "record", which includes all the variable listed in struct 1. Why is it that when ever I attempt to access a variable in the structs, using my vector, I get the error "linked list iterator not dereferencable?"

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  • How to make the tokenizer detect empty spaces while using strtok()

    - by Shadi Al Mahallawy
    I am designing a c++ program, somewhere in the program i need to detect if there is a blank(empty token) next to the token used know eg. if(token1==start) { token2=strtok(NULL," "); if(token2==NULL) {LCCTR=0;} else {LCCTR=atoi(token2);} so in the previous peice token1 is pointing to start , and i want to check if there is anumber next to the start , so I used token2=strtok(NULL," ") to point to the next token but unfortunattly the strtok function cannot detect empty spaces so it gives me an error at run time"INVALID NULL POINTER" how can i fix it or is there another function to use to detect empty spaces #include <iostream> #include<string> #include<map> #include<iomanip> #include<fstream> #include<ctype.h> using namespace std; const int MAX=300; int LCCTR; int START(char* token1); char* PASS1(char*token1); void tokinizer() { ifstream in; ofstream out; char oneline[MAX]; in.open("infile.txt"); out.open("outfile.txt"); if(in.is_open()) { char *token1; in.getline(oneline,MAX); token1 = strtok(oneline," \t"); START (token1); //cout<<'\t'; while(token1!=NULL) { //PASS1(token1); //cout<<token1<<" "; token1=strtok(NULL," \t"); if(NULL==token1) {//cout<<endl; //cout<<LCCTR<<'\t'; in.getline(oneline,MAX); token1 = strtok(oneline," \t"); } } } in.close(); out.close(); } int START(char* token1) { string start("START"); char*token2; if(token1 != start) {LCCTR=0;} else if(token1==start) { token2=strchr(token1+2,' '); cout<<token2; if(token2==NULL) {LCCTR=0;} else {LCCTR=atoi(token2); if(atoi(token2)>9999||atoi(token2)<0){cout<<"IVALID STARTING ADDRESS"<<endl;exit(1);} } } return LCCTR; } char* PASS1 (char*token1) { map<string,int> operations; map<string,int>symtable; map<string,int>::iterator it; pair<map<string,int>::iterator,bool> ret; char*token3=NULL; char*token2=NULL; string test; string comp(" "); string start("START"); string word("WORD"); string byte("BYTE"); string resb("RESB"); string resw("RESW"); string end("END"); operations["ADD"] = 18; operations["AND"] = 40; operations["COMP"] = 28; operations["DIV"] = 24; operations["J"] = 0X3c; operations["JEQ"] =30; operations["JGT"] =34; operations["JLT"] =38; operations["JSUB"] =48; operations["LDA"] =00; operations["LDCH"] =50; operations["LDL"] =55; operations["LDX"] =04; operations["MUL"] =20; operations["OR"] =44; operations["RD"] =0xd8; operations["RSUB"] =0x4c; operations["STA"] =0x0c; operations["STCH"] =54; operations["STL"] =14; operations["STSW"] =0xe8; operations["STX"] =10; operations["SUB"] =0x1c; operations["TD"] =0xe0; operations["TIX"] =0x2c; operations["WD"] =0xdc; if(operations.find("ADD")->first==token1) { token2=strtok(NULL," "); //test=token2; cout<<token2; //if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} //else{LCCTR=LCCTR+3;} } /*else if(operations.find("AND")->first==token1) { token2=strtok(NULL," "); test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("COMP")->first==token1) { token2=token1+5; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("DIV")->first==token1) { token2=token1+4; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("J")->first==token1) { token2=token1+2; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("JEQ")->first==token1) { token2=token1+5; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("JGT")->first==token1) { token2=strtok(NULL," "); test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("JLT")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("JSUB")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("LDA")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("LDCH")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("LDL")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("LDX")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("MUL")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("OR")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("RD")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("RSUB")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("STA")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("STCH")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("STL")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("STSW")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("STX")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("SUB")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("TD")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("TIX")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} } else if(operations.find("WD")->first==token1) { token2=token1+6; test=token2; if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);} else{LCCTR=LCCTR+3;} }*/ //else if( if(word==token1) {LCCTR=LCCTR+3;} else if(byte==token1) {string test; token2=token1+7; test=token2; if(test[0]=='C') {token3=token1+10; test=token3; if(test.length()>15) {cout<<"ERROR"<<endl; exit(1);} } else if(test[0]=='X') {token3=token1+10; test=token3; if(test.length()>14) {cout<<"ERROR"<<endl; exit(1);} } LCCTR=LCCTR+test.length(); } else if(resb==token1) {token3=token1+5; LCCTR=LCCTR+atoi(token3);} else if(resw==token1) {token3=token1+5; LCCTR=LCCTR+3*atoi(token3);} else if(end==token1) {exit(1);} /*else { test=token1; int last=test.length(); if(token1==start||test[0]=='C'||test[0]=='X'||ispunct(test[last])||isdigit(test[0])||isdigit(test[1])||isdigit(test[2])||isdigit(test[3])){} else { token2=strtok(NULL," "); //test=token2; cout<<token2; if(token2!=NULL) { symtable.insert( pair<string,int>(token1,LCCTR)); for(it=symtable.begin() ;it!=symtable.end() ;++it) {/*cout<<"symbol: "<<it->first<<" LCCTR: "<<it->second<<endl;} } else{} } }*/ return token3; } int main() { tokinizer(); return 0; }

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