Re: std::vector : begin, end and insert - Using Objects instead of
ints
Nobody wrote:
Hi,
I thought I would experimenting with vectors.
I am trying to use CPoint objects instead the examples, which use ints.
So, I am a having a few problems.
Question 1.
How do I get the integer value from _Iter or
How do I use _Iter to get the object?
for (_Iter = pt.begin(); _Iter < pt.end(); _Iter++)
{
CPoint& pt = Pts.at(??);
}
I am not sure about the use of begin and end.
Would 0 and size() be the equivalents?
Would there ever be a difference between them?
Question 2.
How do I go about adding CPoint objects with insert?
Do I have to add the object to the front or back of the list,
then move it to the correct position, then delete it from the list?
P.S. I haven't done any experimenting with get_allocator yet.
rend and rbegin aren't finished.
TIA,
/*** Code start ****/.
std::vector<CPoint> m_Pts;
CPoint Pt(2, 4);
Nobody:
You seem to be trying to learn the STL by guessing. This is going to be
hard, because intuitiveness is not the STL's strong suit. Have you
thought of buying a book?
A few points:
1. Iterators are neither pointers nor integers.
2. std::vector has operator [], which always returns a reference (const
reference for const vector). std::vector::at() is the same, except that
is checks that the index is in range.
3. To get the value corresponding to an iterator, dereference it.
4. To get index of vector v from iterator, subtract v.begin() from iterator.
3. To get iterator of vector v from index, add index to v.begin().
4. std::vector::insert() takes iterator as first argument.
5. std::vector::erase() takes iterator as argument.
HTH,
--
David Wilkinson
Visual C++ MVP
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