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  • List.ForEach method and collection interfaces

    - by tyndall
    In .NET 3.5 List< gains a ForEach method. I notice this does not exist on IList< or IEnumerable< what was the thinking here? Is there another way to do this? Nice and simple short way to do this? I ask because I was at a talk where the speaker said always use the more general interfaces. But why would I use IList< as a return type if I want to be able to turn around and use ForEach? Then I would just end up casting it back to a List<.

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  • Difference between a Deprecated and an Legacy API?

    - by Vaibhav Bajpai
    I was studying the legacy API's in the Java's Collection Framework and I learnt that classes such as Vector and HashTable have been superseded by ArrayList and HashMap. However still they are NOT deprecated, and deemed as legacy when essentially, deprecation is applied to software features that are superseded and should be avoided, so, I am not sure when is a API deemed legacy and when it is deprecated.

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  • C++: Trouble with dependent types in templates

    - by Rosarch
    I'm having trouble with templates and dependent types: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> set<result_t> findAll_if(typename set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred) // warning C4346 { set<result_t> result; return findAll_if_rec(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> set<result_t> findAll_if_rec(set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred, set<result_t> result) { typename set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.add(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } Compiler complaints, from the location noted above: warning C4346: 'std::set<result_t>::iterator' : dependent name is not a type. prefix with 'typename' to indicate a type error C2061: syntax error : identifier 'iterator' What am I doing wrong?

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  • Embarassing C++ question regarding const

    - by Neil Butterworth
    My comments on this answer got me thinking about the issues of constness and sorting. I played around a bit and reduced my issues to the fact that this code: #include <vector> int main() { std::vector <const int> v; } will not compile - you can't create a vector of const ints. I suppose I should have known this, but I've never needed to create such a thing before. However, it seems like a useful construct to me, and I wonder if there is any way round this problem - I want to add things to a vector (or whatever), but they should not be changed once added. There's probably some embarrassingly simple solution to this, but it's something I'd never considered before.

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  • What is a truly empty std::vector in C++?

    - by RyanG
    I've got a two vectors in class A that contain other class objects B and C. I know exactly how many elements these vectors are supposed to hold at maximum. In the initializer list of class A's constructor, I initialize these vectors to their max sizes (constants). If I understand this correctly, I now have a vector of objects of class B that have been initialized using their default constructor. Right? When I wrote this code, I thought this was the only way to deal with things. However, I've since learned about std::vector.reserve() and I'd like to achieve something different. I'd like to allocate memory for these vectors to grow as large as possible because adding to them is controlled by user-input, so I don't want frequent resizings. However, I iterate through this vector many, many times per second and I only currently work on objects I've flagged as "active". To have to check a boolean member of class B/C on ever iteration is silly. I don't want these objects to even BE there for my iterators to see when I run through this list. Is reserving the max space ahead of time and using push_back to add a new object to the vector a solution to this?

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  • Getting a java collection of objects in Alphabetical order

    - by MichaelMcCabe
    I have a question that I dont really know where to start. So I thought i'd ask it here. Basically, I have a drop down with names in it. I want these names to be in alphabetical order. Populating the drop down happens as follows; I query a database and pull down an Id and Name, make a object called "UserList", and set the name and id variables with what I get back. I then add this object to an ArrayList. I do this over and over. I then convert this collection to an array, and pass it to my JSP page using session.setAttribute("userList", UserList); I then populate the drop down as below. <c:forEach items="${usersCompanysList}" var="c" > There probably is a simple answer but how to I sort these names?

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  • Access Voilation in std::pair

    - by sameer karjatkar
    I have an application which is trying to populate a pair . Out of no where the application crashes . The Windbg analysis on the crash dump suggest PRIMARY_PROBLEM_CLASS: INVALID_POINTER_READ DEFAULT_BUCKET_ID: INVALID_POINTER_READ STACK_TEXT: 0389f1dc EPFilter32!std::vector,std::allocator ::size+0xc INVALID_POINTER_READ_c0000005_Test.DLL!std::vector_std::pair_unsigned_int, unsigned_int_,std::allocator_std::pair_unsigned_int,unsigned_int___::size Following is the statement in the code where it fails const branch_info& b1 = en1.m_branches[i1]; where branch_info is std::pair and the en1.m_branches[i1] fetches me a pair value

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  • sort std::list case sensitive elements

    - by Dave18
    #include <list> #include <string> using std::string; using std::list; int main() { list <string> list_; list_.push_back("C"); list_.push_back("a"); list_.push_back("b"); list_.sort(); } does sort() function sort the elements according to their character codes? I want the result here to be a b C after the sorting is done.

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  • Deleting a element from a vector of pointers in C++.

    - by Kranar
    I remember hearing that the following code is not C++ compliant and was hoping someone with much more C++ legalese than me would be able to confirm or deny it. std::vector<int*> intList; intList.push_back(new int(2)); intList.push_back(new int(10)); intList.push_back(new int(17)); for(std::vector<int*>::iterator i = intList.begin(); i != intList.end(); ++i) { delete *i; } intList.clear() The rationale was that it is illegal for a vector to contain pointers to invalid memory. Now obviously my example will compile and it will even work on all compilers I know of, but is it standard compliant C++ or am I supposed to do the following, which I was told is in fact the standard compliant approach: while(!intList.empty()) { int* element = intList.back(); intList.pop_back(); delete element; }

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  • .NET Garbage Collection behavior (with DataTable)

    - by gmac
    I am wonder why after creating a very simple DataTable and then setting it to null why Garbage Collection does not clear out all the memory used by that DataTable. Here is an example. The variable Before should be equal to Removed but it is not. { long Before = 0, After = 0, Removed = 0, Collected = 0; Before = GC.GetTotalMemory(true); DataTable dt = GetSomeDataTableFromSql(); After = GC.GetTotalMemory(true); dt = null; Removed = GC.GetTotalMemory(true); GC.Collect(); Collected = GC.GetTotalMemory(true); } Gives the following results. Before = 388116 After = 731248 Removed = 530176 Collected = 530176

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  • how to specify a pointer to an overloaded function?

    - by davka
    I want to pass an overloaded function to the std::for_each() algorithm. e.g.: void f(char c); void f(int i); std::string s("example"); std::for_each(s.begin(), s.end(), f); I'd expect the compiler to resolve f() by the iterator type. Apparently, it (gcc 4.1.2) doesn't do it. So, how can I specify which f() I want? thanks a lot

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  • Bind to a collection's view and just call ToString()

    - by womp
    I'm binding a GridView to a collection of objects that look like this: public class Transaction { public string PersonName { get; set; } public DateTime TransactionDate { get; set; } public MoneyCollection TransactedMoney { get; set;} } MoneyCollection simply inherits from ObservableCollection<T>, and is a collection of MyMoney type object. In my GridView, I just want to bind a column to the MoneyCollection's ToString() method. However, binding it directly to the TransactedMoney property makes every entry display the text "(Collection)", and the ToString() method is never called. I understand that it is binding to the collection's default view. So my question is - how can I make it bind to the collection in such a way that it calls the ToString() method on it? This is my first WPF project, so I know this might be a bit noobish, but pointers would be very welcome.

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  • Java: Efficient Equivalent to Removing while Iterating a Collection

    - by Claudiu
    Hello everyone. We all know you can't do this: for (Object i : l) if (condition(i)) l.remove(i); ConcurrentModificationException etc... this apparently works sometimes, but not always. Here's some specific code: public static void main(String[] args) { Collection<Integer> l = new ArrayList<Integer>(); for (int i=0; i < 10; ++i) { l.add(new Integer(4)); l.add(new Integer(5)); l.add(new Integer(6)); } for (Integer i : l) { if (i.intValue() == 5) l.remove(i); } System.out.println(l); } This, of course, results in: Exception in thread "main" java.util.ConcurrentModificationException ...even though multiple threads aren't doing it... Anyway. What's the best solution to this problem? "Best" here means most time and space efficient (I realize you can't always have both!) I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.

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  • is this possible: c# collection of Type with constrains, or collection of generic type?

    - by Jon
    I'm trying to store types in a collection, so that i can later instantiate objects of the types in the collection. But I'm not sure how to do this the best way. What i have so far: List<Type> list = new List<Type>(); list.Add(typeof(MyClass)); var obj = (MyClass)Activator.CreateInstance(list[0]); I would like to have some constrains on the Type, or better yet, just a generic type in the collection instead of an instantiated Type object. Is this possible?

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