Re: Iterator questions...
barcaroller wrote:
On May 15, 11:54 pm, "Jim Langston" <tazmas...@rocketmail.com> wrote:
One of the most common uses of .begin() and .end() is in a for loop,
such as:
std::list<int> Data;
for ( std::list<int>::iterator it = Data.begin(); it != Data.end();
++it ) {
// it is guaranteed to be pointing to an item in the list
}
Actually, I'm not using the iterator in a loop. Briefly, I save the
iterator of the last successful find(). Before I call find() again, I
first check if the last iterator points to the info that I need. If
not, then I
call find(). In essence, I'm caching the iterator to improve
performance, by avoiding a call to find().
Note: where find() is either a member function or an algorithm.
However, caching iterators has its own problems. Initialization,
invalidation, etc.
..find() can and will return .end() if the item was not found. You need to
test for this and not attempt to dereference the iterator if it is .end().
Also be aware that you are "saving the iterator". Be sure there is no
interventing changes to the vector that can invalidate your reference.
Without seeing your actual code I can not say for certain why the
dereference is not working, only that there is something you are not taking
into account, most likely the iterator pointing to .end() or being
invalidated because of operations on the container.
--
Jim Langston
tazmaster@rocketmail.com