Slicing a vector

Question

I have a std::vector. I want to create iterators representing a slice of that vector. How do I do it. In psudo C++:

class InterestingType;

void doSomething(slice& s) {
    for (slice::iterator i = s.begin(); i != s.end(); ++i) {
       std::cout << *i << endl;
    }
}
int main() {
   std::vector v();
   for (int i= 0; i < 10; ++i) { v.push_back(i); }
   slice slice1 = slice(v, 1, 5);
   slice slice2 = slice(v, 2, 4);
   doSomething(slice1);
   doSomething(slice2);
   return 0;
}

I would prefer not to have to copy the elements to a new datastructure.

Answer 1

You can represent those "slices" with a pair of iterators.

Answer 2

You'd just use a pair of iterators:

typedef std::vector<int>::iterator vec_iter;

void doSomething(vec_iter first, vec_iter last) {
    for (vec_iter cur = first; cur != last; ++cur) {
       std::cout << *cur << endl;
    }
}

int main() {
   std::vector v();
   for (int i= 0; i < 10; ++i) { v.push_back(i); }

   doSomething(v.begin() + 1, v.begin() + 5);
   doSomething(v.begin() + 2, v.begin() + 4);
   return 0;
}

Alternatively, the Boost.Range library should allow you to represent iterator pairs as a single object, but the above is the canonical way to do it.

Answer 3

As others have said, you can represent the "slice" as pair of iterators. If you are willing to use Boost, you can use the range concept. Then you will have even begin()/end() member functions available and the whole thing looks a lot like a container.