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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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  • STL map - insert or update

    - by CodeJunkie
    I have a map of objects and I want to update the object mapped to a key, or create a new object and insert into the map. The update is done by a different function that takes a pointer to the object (void update(MyClass *obj)) What is the best way to "insert or update" an element in a map?

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  • C++ STL question related to insert iterators and overloaded operators

    - by rshepherd
    #include <list> #include <set> #include <iterator> #include <algorithm> using namespace std; class MyContainer { public: string value; MyContainer& operator=(const string& s) { this->value = s; return *this; } }; int main() { list<string> strings; strings.push_back("0"); strings.push_back("1"); strings.push_back("2"); set<MyContainer> containers; copy(strings.begin(), strings.end(), inserter(containers, containers.end())); } The preceeding code does not compile. In standard C++ fashion the error output is verbose and difficult to understand. The key part seems to be this... /usr/include/c++/4.4/bits/stl_algobase.h:313: error: no match for ‘operator=’ in ‘__result.std::insert_iterator::operator* [with _Container = std::set, std::allocator ]() = __first.std::_List_iterator::operator* [with _Tp = std::basic_string, std::allocator ]()’ ...which I interpet to mean that the assignment operator needed is not defined. I took a look at the source code for insert_iterator and noted that it has overloaded the assignment operator. The copy algorithm must uses the insert iterators overloaded assignment operator to do its work(?). I guess that because my input iterator is on a container of strings and my output iterator is on a container of MyContainers that the overloaded insert_iterator assignment operator can no longer work. This is my best guess, but I am probably wrong. So, why exactly does this not work and how can I accomplish what I am trying to do?

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  • c++ STL vector is not acccepting the copy constructor

    - by prabhakaran
    I wrote a code ( c++,visual studio 2010) which is having a vector, even I though copy const is declared, but is still showing that copy const is not declared Here the code #include<iostream> #include<vector> using namespace std; class A { public: A(){cout << "Default A is acting" << endl ;} A(A &a){cout << "Copy Constructor of A is acting" << endl ;} }; int main() { A a; A b=a; vector<A> nothing; nothing.push_back(a); int n; cin >> n; } The error I got is Error 1 error C2558: class 'A' : no copy constructor available or copy constructor is declared 'explicit' c:\program files\microsoft visual studio 10.0\vc\include\xmemory 48 1 delete Anybody please help me

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  • deleting dynamically allocated object that contains vector in C++ STL

    - by kobac
    I have a class class ChartLine{ protected: vector<Point> line; // points connecting the line CString name; //line name for legend CPen pen; //color, size and style properties of the line }; where Point is a structure struct Point{ CString x; double y; }; In main() I dynamically allocate objects of type ChartLine with new operator. If I use delete afterwards, will default destructor ~ChartLine() properly dealocate (or clear) member ChartLine::line(which is vector btw) or I would have to clear that vector in ~ChartLine() manually? Thanks in advance. Cheers.

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  • STL: how to overload operator= for <vector> ?

    - by MBes
    There's simple example: #include <vector> int main() { vector<int> veci; vector<double> vecd; for(int i = 0;i<10;++i){ veci.push_back(i); vecd.push_back(i); } vecd = veci; // <- THE PROBLEM } The thing I need to know is how to overload operator = so that I could make assignment like this: vector<double> = vector<int>; I've just tried a lot of ways, but always compiler has been returning errors... Is there any option to make this code work without changing it? I can write some additional lines, but can't edit or delete the existing ones. Ty.

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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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  • How to change a particular element of a C++ STL vector

    - by cambr
    vector<int> l; for(int i=1;i<=10;i++){ l.push_back(i); } Now, for example, how do I change the 5th element of the vector to -1? I tried l.assign(4, -1); It is not behaving as expected. None of the other vector methods seem to fit. I have used vector as I need random access functionality in my code (using l.at(i)).

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  • lambda+for_each+delete on STL containers

    - by rubenvb
    I'm trying to get a simple delete every pointer in my vector/list/... function written with an ultra cool lambda function. Mind you, I don't know c**p about those things :) template <typename T> void delete_clear(T const& cont) { for_each(T.begin(), T.end(), [](???){ ???->delete() } ); T.clear(); } I have no clue what to fill in for the ???'s. Any help is greatly appreciated!

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  • C++ STL: Array vs Vector: Raw element accessing performance

    - by oh boy
    I'm building an interpreter and as I'm aiming for raw speed this time, every clock cycle matters for me in this (raw) case. Do you have any experience or information what of the both is faster: Vector or Array? All what matters is the speed I can access an element (opcode receiving), I don't care about inserting, allocation, sorting, etc. I'm going to lean myself out of the window now and say: Arrays are at least a bit faster than vectors in terms of accessing an element i. It seems really logical for me. With vectors you have all those security and controlling overhead which doesn't exist for arrays. (Why) Am I wrong? No, I can't ignore the performance difference - even if it is so small - I have already optimized and minimized every other part of the VM which executes the opcodes :)

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  • C++ STL 101: Overload function causes build error

    - by Sidjal
    Trivial code that works if I do not overload myfunc. void myfunc(int i) { std::cout << "calling myfunc with arg " << i << std::endl; } void myfunc(std::string s) { std::cout << "calling myfunc with arg " << s << std::endl; } void testalgos() { std::vector<int> v; v.push_back(1); v.push_back(2); std::vector<std::string> s; s.push_back("one"); s.push_back("two"); std::for_each( v.begin(), v.end(), myfunc); std::for_each( s.begin(), s.end(), myfunc); return; } int _tmain(int argc, _TCHAR* argv[]) { std::cout << "Hello World" << std::endl; testalgos(); return 0; } The following build errors repeat for both for_each calls. error C2914: 'std::for_each' : cannot deduce template argument as function argument is ambiguous error C2784: '_Fn1 std::for_each(_InIt,_InIt,_Fn1)' : could not deduce template argument for '_InIt' from 'std::_Vector_iterator<_Ty,_Alloc'. It does work if I do not overload myfunc.Can someone explain what is happening here. TIA

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  • C++ STL: Trouble with string iterators

    - by Rosarch
    I'm making a simple command line Hangman game. void Hangman::printStatus() { cout << "Lives remaining: " << livesRemaining << endl; cout << getFormattedAnswer() << endl; } string Hangman::getFormattedAnswer() { return getFormattedAnswerFrom(correctAnswer.begin(), correctAnswer.end()); } string Hangman::getFormattedAnswerFrom(string::const_iterator begin, string::const_iterator end) { return begin == end? "" : displayChar(*begin) + getFormattedAnswerFrom(++begin, end); } char Hangman::displayChar(const char c) { return c; } (Eventually, I'll change this so displayChar() displays a - or a character if the user has guessed it, but for simplicity now I'm just returning everything.) When I build and run this from VS 2010, I get a popup box: Debug Assertion Failed! xstring Line: 78 Expression: string iterator not dereferenceable What am I doing wrong?

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  • Need help with map (c++, STL)

    - by Mike Dooley
    Hi folks! Actually I'm new to C++. I tried something out (actually the map container) but it doesn't work the way I assumed it will... Before posting my code, I will explain it shortly. I created 3 classes: ClassA ClassDerivedA ClassAnotherDerivedA The two last ones are derived from "ClassA". Further I created a map: map<string,ClassA> test_map; I put some objects (from Type ClassDerivedA and ClassAnotherDerivedA) into the map. Keep in mind: the mapped value is from type "ClassA". This will only work because of Polymorphism. Finally I created an iterator which runs over my map and compares the user input with my keys in the map. If they match, it will call a specific method called "printOutput". And there is the Problem: Although i declared "printOutput" as "virtual" the only method called is the one from my base class, but why? and here is the code: #include <iostream> #include <map> using namespace std; class ClassA { public: virtual void printOutput() { cout << "ClassA" << endl; } }; class ClassDerivedA : public ClassA { public: void printOutput() { cout << "ClassDerivedA" << endl; } }; class ClassAnotherDerivedA: public ClassA { public: void printOutput() { cout << "ClassAnotherDerivedA" << endl; } }; int main() { ClassDerivedA class_derived_a; ClassAnotherDerivedA class_another_a; map<string,ClassA> test_map; test_map.insert(pair<string,ClassA>("deriveda", class_derived_a)); test_map.insert(pair<string,ClassA>("anothera", class_another_a)); string s; while( cin >> s ) { if( s != "quit" ) { map<string,ClassA>::iterator it = test_map.find(s); if(it != test_map.end()) it->second.printOutput(); } else break; } } Blockquote

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  • C++ STL list vs set

    - by mokaschitta
    Hi, what of those two is faster for random insertions and deletions? I guess list, having the values as the keys as it is with sets seems to be attractive too though. Is performance similar for iterating over the whole container? Thanks!

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  • [c++/STL] Selective iterator

    - by rubenvb
    FYI: no boost, yes it has this, I want to reinvent the wheel ;) Is there some form of a selective iterator (possible) in C++? What I want is to seperate strings like this: some:word{or other to a form like this: some : word { or other I can do that with two loops and find_first_of(":") and ("{") but this seems (very) inefficient to me. I thought that maybe there would be a way to create/define/write an iterator that would iterate over all these values with for_each. I fear this will have me writing a full-fledged custom way-too-complex iterator class for a std::string. So I thought maybe this would do: std::vector<size_t> list; size_t index = mystring.find(":"); while( index != std::string::npos ) { list.push_back(index); index = mystring.find(":", list.back()); } std::for_each(list.begin(), list.end(), addSpaces(mystring)); This looks messy to me, and I'm quite sure a more elegant way of doing this exists. But I can't think of it. Anyone have a bright idea? Thanks PS: I did not test the code posted, just a quick write-up of what I would try

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  • A map and set which uses contiguous memory and has a reserve function

    - by edA-qa mort-ora-y
    I use several maps and sets. The lack of contiguous memory, and high number of (de)allocations, is a performance bottleneck. I need a mainly STL-compatbile map and set class which can use a contiguous block of memory for internal objects (or multiple blocks). It also needs to have a reserve function so that I can preallocate for expected sizes. Before I write my own I'd like to check what is available first. Is there something in Boost which does this? Does somebody know of an available implementation elsewhere? Intrusive collection types are not usable here as the same objects need to exist in several collections. As far as I know STL memory pools are per-type, not per instance. These global pools are not efficient with respect to memory locality in mutli-cpu/core processing. Object pools don't work as the types will be shared between instance but their pool should not. In many cases a hash map may be an option in some cases.

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  • Rewrite arrays using collections

    - by owca
    I have a task, which I was able to do with the use of simplest methods - arrays. Now I'd like to go further and redo it using some more complicated java features like collections, but I've never used anything more complicated than 2d matrix. What should I look at and how to start with it. Should Tower become a Collection ? And here's the task : We have two classes - Tower and Block. Towers are built from Blocks. Ande here's sample code for testing: Block k1=new Block("yellow",1,5,4); Block k2=new Block("blue",2,2,6); Block k3=new Block("green",3,4,2); Block k4=new Block("yellow",1,5,4); Tower tower=new Tower(); tower.add(k1,k2,k3); "Added 3 blocks." System.out.println(tower); "block: green, base: 4cm x 3cm, thicknes: 2 cm block: blue, base: 6cm x 2cm, thicknes: 2 cm block: yellow, base: 5cm x 4cm, thicknes: 1 cm" tower.add(k2); "Tower already contains this block." tower.add(k4); "Added 1 block." System.out.println(tower); "block: green, base: 4cm x 3cm, thicknes: 2 cm block: blue, base: 6cm x 2cm, thicknes: 2 cm block: yellow, base: 5cm x 4cm, thicknes: 1 cm block: yellow, base: 5cm x 4cm, thicknes: 1 cm" tower.delete(k1); "Deleted 1 block" tower.delete(k1); "Block not in tower" System.out.println(tower); "block: blue, base: 6cm x 2cm, thicknes: 2 cm block: yellow, base: 5cm x 4cm, thicknes: 1 cm block: yellow, base: 5cm x 4cm, thicknes: 1 cm" Let's say I will treat Tower as a collection of blocks. How to perform search for specific block among whole collection ? Or should I use other interface ?

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  • Database access through collections

    - by Mike
    Hi All, I have an 3 tiered application where I need to get database results and populated the UI. I have a MessagesCollection class that deals with messages. I load my user from the database. On the instantiation of a user (ie. new User()), a MessageCollection Messages = new MessageCollection(this) is performed. Message collection accepts a user as a parameter. User user = user.LoadUser("bob"); I want to get the messages for Bob. user.Messages.GetUnreadMessages(); GetUnreadMessages calls my Business Data provider which in turn calls the data access layer. The Business data provider returns List. My question is - I am not sure what the best practice is here - If I have a collection of messages in an array inside the MessagesCollection class, I could implement ICollection to provide GetEnumerator() and ability to traverse the messages. But what happens if the messages change and the the user has old messages loaded? What about big message collections? What if my user had 10,000 unread messages? I don't think accessing the database and returning 10,000 Message objects would be efficient.

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  • Manipulating collections & the ViewModel pattern

    - by Kragen
    I'm relatively new to WPF, and I'm having trouble with what I'm fairly certain is a relatively simple problem. I have my underlying data object, a Person: class Person { public string Surname {get; set; } public string Firstname {get; set; } public List<Address> Addresses {get; } } And I wish to display and edit this object in my WPF app. To this end I've created a ViewModel that I bind to in my xaml: class PersonViewModel { public string Fullname {get; } public ObservableCollection<AddressViewModel> Addresses {get; } } This is fine, except when it comes to manipulating my Address collection, where I can't work out what I should be doing: Should I add methods AddAddress, RemoveAddress etc... to my PersonViewModel class for manipulating my collection with instances of AddressViewModel Should I just add instances of AddressViewModel to my Addresses observable collection Both of the above seem a bit messy - is there a better way of dealing with collections?

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  • Minimal framework in Scala for collections with inheriting return type

    - by Rex Kerr
    Suppose one wants to build a novel generic class, Novel[A]. This class will contain lots of useful methods--perhaps it is a type of collection--and therefore you want to subclass it. But you want the methods to return the type of the subclass, not the original type. In Scala 2.8, what is the minimal amount of work one has to do so that methods of that class will return the relevant subclass, not the original? For example, class Novel[A] /* What goes here? */ { /* Must you have stuff here? */ def reverse/* What goes here instead of :Novel[A]? */ = //... def revrev/*?*/ = reverse.reverse } class ShortStory[A] extends Novel[A] /* What goes here? */ { override def reverse: /*?*/ = //... } val ss = new ShortStory[String] val ss2 = ss.revrev // Type had better be ShortStory[String], not Novel[String] Does this minimal amount change if you want Novel to be covariant? (The 2.8 collections do this among other things, but they also play with return types in more fancy (and useful) ways--the question is how little framework one can get away with if one only wants this subtypes-always-return-subtypes feature.)

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  • Intersection() and Except() is too slow with large collections of custom objects

    - by Theo
    I am importing data from another database. My process is importing data from a remote DB into a List<DataModel> named remoteData and also importing data from the local DB into a List<DataModel> named localData. I am then using LINQ to create a list of records that are different so that I can update the local DB to match the data pulled from remote DB. Like this: var outdatedData = this.localData.Intersect(this.remoteData, new OutdatedDataComparer()).ToList(); I am then using LINQ to create a list of records that no longer exist in remoteData, but do exist in localData, so that I delete them from local database. Like this: var oldData = this.localData.Except(this.remoteData, new MatchingDataComparer()).ToList(); I am then using LINQ to do the opposite of the above to add the new data to the local database. Like this: var newData = this.remoteData.Except(this.localData, new MatchingDataComparer()).ToList(); Each collection imports about 70k records, and each of the 3 LINQ operation take between 5 - 10 minutes to complete. How can I make this faster? Here is the object the collections are using: internal class DataModel { public string Key1{ get; set; } public string Key2{ get; set; } public string Value1{ get; set; } public string Value2{ get; set; } public byte? Value3{ get; set; } } The comparer used to check for outdated records: class OutdatedDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { var e = string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2) && ( !string.Equals(x.Value1, y.Value1) || !string.Equals(x.Value2, y.Value2) || x.Value3 != y.Value3 ); return e; } public int GetHashCode(DataModel obj) { return 0; } } The comparer used to find old and new records: internal class MatchingDataComparer : IEqualityComparer<DataModel> { public bool Equals(DataModel x, DataModel y) { return string.Equals(x.Key1, y.Key1) && string.Equals(x.Key2, y.Key2); } public int GetHashCode(DataModel obj) { return 0; } }

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  • Why does std queue not define a swap method specialisation

    - by Jamie Cook
    I've read that all stl containers provide a specialisation of the swap algorithm so as to avoid calling the copy constructor and two assignment operations that the default method uses. However, when I thought it would be nice to use a queue in some code I was working on I noticed that (unlike vector and deque) queue doesn't provide this method? I just decided to use a deque instead of a queue, but still I'm interested to know why this is?

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