using std::list<>::iterator?

I had these statements in my prog:

Code:

#include <iostream>
#include <fstream>
#include <cmath>
#include <list>
using std::list;
using std::ofstream;
using std::cout;
using std::cin;

and when I tried to advance my iters, I got infinite loops.

Do I have to say something like:

Code:

using std::list<>::iterator;

????????????

Your infinite loops probably have absolutely nothing to do with "using" statements.

I should add that if I just said:

using namespace std;


everything works fine.



it all seems unrelated to me but maybe you C++ gods know better

yeah that's what i figured. i guess it wouldn't have let me even declare an iterator if that was the case. anyway, i just had to hold down ctrl-z until it backed my prog up to where it was working okay. (how's that for debugging a program, haha!)

What does your loop look like?

I basically had a function like this:

Code:

list<Coordinates>::iterator partition_segment(list<Coordinates>& mList, list<Coordinates>::iterator it){

    list<Coordinates> tempList;

    double xPos = it->get_x();

    ++it;

    double nextXPos = it->get_x();

    // Do stuff with my data here

    // Populate my temp list:
    tempList.push_back(aCoordinate);
    tempList.push_back(aCoordinate2);
    tempList.push_back(aCoordinate3);

    mList.splice(it, tempList);

    return it;
}

This function was called in main like so:

Code:

for(int i = 0; i < numLoops; i++){

    list<Coordinate>::iterator pos = aList.begin();

    while(pos != aList.end()){

        pos = partition_segment(aList, pos);
    }
}

it works fine now, and I undid so many things that I won't know where the problem was now.

What does splice do? If it modifies mList (it appears that it might) then it is a mistake, because it would (possibly) invalidate your iterator. The basic rule is if you modify a container any iterator pointing into that container is not guaranteed to be valid afterwords.

The basic rule is if you modify a container any iterator pointing into that container is not guaranteed to be valid afterwords.

This does not apply to std::list: inserting and deleting elements from a std::list does not invalidate pointers, references and iterators to other elements of that std::list.

Originally Posted by IfYouSaySo

What does splice do? If it modifies mList (it appears that it might) then it is a mistake, because it would (possibly) invalidate your iterator. The basic rule is if you modify a container any iterator pointing into that container is not guaranteed to be valid afterwords.

http://www.cppreference.com/cpplist/splice.html

It inserts one list into another list at the specified position.
I don't believe it invalidates any iterators since this is a list, not a vector.