dev-cpp-users

[Dev-C++] Problem deleting iterator contents while iterating...

[Edric T. <pp...@ho...>]

Hi guys,

I've ran into a small problem here...
What I'm trying to do is to iterate through an STL data structure. On a =
successful match in criteria, I wish to delete the iterator and its =
contents away from the memory. However, when I attempted to call delete =
on the node that I want to remove, the compilation throws an error. =
Anyone knows what's going on? Here's the code for your reference:

for (ResultTable::iterator xIter=3DresultTable.begin(); =
xIter!=3DresultTable.end(); ) {
        if (!matchFound) {
                // Match was unsuccessfull
                // TODO:
                //      Free memory allocated to this node
                    delete(*xIter); // Compilation fails at this point
                    resultTable.erase(xIter++);
        }
        else {
                // Match was successful begin copying the additional =
columns=20
                // over from y
                    ++xIter;
        }
}

Thanks and regards,
Ed

Re: [Dev-C++] Problem deleting iterator contents while iterating...

[Vale G. <val...@at...>]

Edric -

> On a successful match in criteria, I wish to delete the iterator and its
contents away from the memory.

The nice thing about STLs is that they take care of all of the fiddly bits for
you.

I'm not sure that an STL container implementation is required to free up the
memory used by a deleted member.  Don't worry about it.

> However, when I attempted to call delete on the node that I want to remove,
the compilation throws an error.
> delete(*xIter); // Compilation fails at this point

I don't think that you can dereference an iterator. Eliminate the line that
won't compile.  It's not needed.  The member is erased by the line:

resultTable.erase(xIter++);

but

Danger! Danger! If the container is a vector, string or deque, the iterator is
invalid after the erase.

It's too much to go into here.  For more information, see Item 9 in Scott
Meyer's Effective STL book.  Nicolai Josuttis' The C++ Standard Library would
also be a very good investment.

Chuck