variable was not declared in this scope

Question

I have the following code:

typename List<Pair>::Iterator Iterator; int changeTableSize(int newSize, int originalSize){ List<Pair>* temp = new List<Pair>[newSize]; for (int i = 0; i < originalSize; i++){ for (Iterator j = elements[i].begin(); j != elements[i].end(); j++){ Pair p = *j; temp[p.key % newSize].insert(p); } } delete elements; elements = temp; return newSize; }

The compiler says that j was not declared in this scope. What can cause this?

(Note that List and Pair are implemented by me)

What is the type of elements? Your question lacks some context. — leemes
– leemes, Commented Jan 4, 2014 at 19:16

Cheers and hth. - Alf · Accepted Answer · 2014-01-04 19:48:29Z

The problem.

The statement

typename List<Pair>::Iterator Iterator;

declares Iterator as a variable.

It's no longer a type.

Fix.

Did you mean to write typedef, not typename?

That would fix the immediate problem, but not future problems of this kind.

To generally avoid such problems, use C++11 auto for iterators as loop control variables.

Other comments.

Instead of explicitly using new and delete to implement a dynamically sized array, consider just using std::vector. Much more convenient, safe, etc. etc. Less work, more enjoyable!

Miguel · Accepted Answer · 2014-01-04 19:18:39Z

"Iterator" is it supposed to be a c++ iterator? Because if it is, then that's where the problem is. Use Keyword auto for j and it should do it.

The reason it's giving you the error is because iterator is not fully/properly declared/initialized.

remember that iterators are template classes so by that you should inmediately know that it requires at least one template parameter i.e. forward_list<int>::iterator.

Tom Kerr · Accepted Answer · 2014-01-04 19:16:26Z

If Iterator is not fully defined you may get this error. Usually you'd see errors about the type being undefined before that though.

Or maybe if you're using an ancient MS compiler.

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The problem.

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