The objects in the std::set are stored as const StudentT. So when you try to call getId() with the const object the compiler detects a problem, mainly you’re calling a non-const member function on const object which is not allowed because non-const member functions make NO PROMISE not to modify the object; so the compiler … Read more
You can do something like: std::set<int> s1; std::set<int> s2; // fill your sets s1.insert(s2.begin(), s2.end());
STL has no built in thread support, so you’ll have to extend the STL code with your own synchronization mechanisms to use STL in a multithreaded environment. For example look here: link text Since set is a container class MSDN has following to say about the thread safety of the containers. A single object is … Read more
Both std::set and std::map are associative containers. The difference is that std::sets contain only the key, while in std::map there is an associated value. Choosing one over the other depends mainly on what the task at hand is. If you want to build a dictionary of all the words that appear in a text, you … Read more
A set is like a map with no values, only keys. Since those keys are used for a tree that accelerates operations on the set, they cannot change. Thus all elements must be const to keep the constraints of the underlying tree from being broken.
What comparator are you using? For the default this will work: if(!myset.empty()) *myset.rbegin(); else //the set is empty This will also be constant time instead of linear like the max_element solution.
Yes there is, it is in <algorithm> and is called: std::set_difference. The usage is: #include <algorithm> #include <set> #include <iterator> // … std::set<int> s1, s2; // Fill in s1 and s2 with values std::set<int> result; std::set_difference(s1.begin(), s1.end(), s2.begin(), s2.end(), std::inserter(result, result.end())); In the end, the set result will contain the s1-s2.
I think it was probably because they were trying to make std::set and std::multiset as similar as possible. (And obviously count has a perfectly sensible meaning for std::multiset.) Personally I think this was a mistake. It doesn’t look quite so bad if you pretend that count is just a misspelling of contains and write the … Read more
You haven’t provided an output iterator for set_intersection template <class InputIterator1, class InputIterator2, class OutputIterator> OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result ); Fix this by doing something like …; set<int> intersect; set_intersection(s1.begin(), s1.end(), s2.begin(), s2.end(), std::inserter(intersect, intersect.begin())); You need a std::insert iterator since the set is as of … Read more
You need to use a back_inserter: std::copy(input.begin(), input.end(), std::back_inserter(output)); std::copy doesn’t add elements to the container into which you are inserting: it can’t; it only has an iterator into the container. Because of this, if you pass an output iterator directly to std::copy, you must make sure it points to a range that is at … Read more