[fpc-devel] New feature discussion: for-in loop

[Vinzent Hoefler]

On Monday 26 October 2009, Micha Nelissen wrote:
> Vinzent Höfler wrote:
> > At first, "const function" would tell us that the function does not
> > change the object in any way, right?
>
> What is "the object"?

In that case, the list, of course.

> Usually there are 2 objects: the list (TList 
> e.g.) and the object being iterated, e.g. TList.Objects[I]. Those
> referenced objects can be volatile, the const-ness only applies to
> the TList.

Yes, that's what I thought.

> Ideally the iterator state and the state of the items 
> iterated over are separated. (Maybe this is not so with e.g.
> TStringList).

Suppose, the list items have a property "Owner" and the iterator calls 
some method that says "Owner.Delete (self);" somewhere. How's the 
compiler supposed to detect that?

In some languages, this problem is circumvented by creating a copy of 
the list before iterating the set, but I don't think that this is a 
viable solution for Pascal (or any compiled language, for that matter).


Vinzent.