I'm trying to figure out the best way to design a couple of classes. I'm pretty new to Python (and OOP in general) and just want to make sure that I'm doing this right. I have two classes: "Users" and "User". class User(object): def __init__(self): pass class Users(object): def __init__(self): self.users = [] ...
C# 2 and VB.Net 8 introduced a new feature called iterators, which were designed to make it easier to return enumerables and enumerators. However, iterators are actually a limited form of coroutines, and can be used to do many useful things that have nothing to do with collections of objects. What non-standard uses of iterators have yo...
I read in The C++ Programming Language : Special Edition Don't use iterators into a resized vector Consider this example. vector< int >::iterator it = foo.begin(); while ( it != foo.end() ) { if ( // something ) { foo.push_back( // some num ); } ++it; } Is there a problem with this? After the vector was resized, would the...
I am having a problem using const reverse iterators on non-const containers with gcc. Well, only certain versions of gcc. #include <vector> #include <iostream> using namespace std; int main() { const char v0[4] = "abc"; vector<char> v(v0, v0 + 3); // This block works fine vector<char>::const_iterator i; for (i = ...
What must I do in order to be able to return an Iterator from a method/class ? How would one add that trait to a class? ...
What's the best way of getting the last item from an iterator in Python 2.6? For example, say my_iter = iter(range(5)) What is the shortest-code / cleanest way of getting 4 from my_iter? I could do this, but it doesn't seem very efficient: [x for x in my_iter][-1] ...
I need to traverse a LinkedList a number of times, in a way that suggests using ListIterator. Is there a way to reset a ListIterator? or is it better to just create a new one? (and what if I can't because I don't have access to the list?) edit: and is there a way to create a ListIterator that points to the end of the list? (so that has...
I'm implementing a custom container with an STL-like interface. I have to provide a regular iterator and a const iterator. Most of the code for the two versions of the iterators is identical . How can I avoid this duplication? For example, my container class is Foo, and I'm implementating FooIterator and FooConstIterator. Both of th...
is it possible to iterate through until the end of list in main() function using the const_iterator? I tried using iter->end() but i can't figure it out. #include <list> #include <string> using std::list; using std::string; class list_return { public: list <string>::const_iterator get_list() { _list.push_back("1"); _list.push_back("2")...
I need to loop over a list of objects, comparing them like this: 0 vs. 1, 1 vs. 2, 2 vs. 3, etc. (I'm using pysvn to extract a list of diffs.) I wound up just looping over an index, but I keep wondering if there's some way to do it which is more closely idiomatic. It's Python; shouldn't I be using iterators in some clever way? Simply loo...
I'm iterating over a vector and need the index the iterator is currently pointing at. AFAIK this can be done in two ways: it - vec.begin() std::distance(vec.begin(), it) Which one is better or preferred and why? ...
1 of the presentation says "These methods are LAZY!" Iterable transform(Iterable, Function)* Iterable filter(Iterable, Predicate)* T find(Iterable<T>, Predicate) Iterable concat(Iterable<Iterable>) Iterable cycle(Iterable) T getOnlyElement(Iterable<T>) Iterable<T> reverse(List<T>) Can someone help me understand what they mean by this,...
If we do the following we get error: class FGH{ public static Iterator reverse(List list) { Collections.reverse(list); return list.iterator(); } public static void main(String[] args) { List list = new ArrayList(); list.add("1"); list.add("2"); list.add("3"); /*for(Iterator it:reverse(list)) Iter...
I'm using a boost variant to hold some generated types, right now my code generator creates a header with the types and a variant capable of holding them. At initialization time, I'd like to iterate over the allowable types in the variant, not the types the variant is holding at the moment. Can I do this with a variant? ...
I have an ArrayList and I am using an iterator to run through it. I need to find out what type of object is next: Iterator vehicleIterator = vehicleArrayList.iterator(); while(vehicleIterator.hasNext()) { //How do I find the type of object in the arraylist at this point // for example, is it a car, bus etc... } Thanks ...
Does an instance of an Iterator opened on a collection keep the whole collection in memory and access a position that increments every time next() is called? Or am I missing something? ...
I am trying to write a simple STL iterator for CArray MFC class using boost iterator adaptor. This is my code: #include <boost/iterator/iterator_adaptor.hpp> #include <afxtempl.h> class CArrIter : public boost::iterator_adaptor< CArrIter , int, int, boost::random_access_traversal_tag > { public: CArrIter(CArray<int,in...
I have an implementation of java.util.Iterator which requires that the call to next() should always be proceeded by a call to hasNext(). (This is because results are returned asynchronosly in a multi threaded environment and it is never clear how many more results there might be). Would it be 'correct' to properly document this in the J...
I've already looked at this question: http://stackoverflow.com/questions/1152238/python-iterators-how-to-dynamically-assign-self-next-within-a-new-style-class but this doesn't help me because I want to iterate of an attribute of the error which is a list (ie, already iterable) without having to use the attribute explicitly. I'm looking ...
I've a custom container which is implemented in two different ways, but with a single interface. some thing like this. class Vector { virtual Iterator begin() = 0; virtual Iterator end () = 0 ; ... // some more functions. } ; class VectorImplA : public Vector { Iterator begin() { return m_...