foreach, an analogy

[Karen Lanrap]

Bill Baxter wrote:

>>> The call stack stores our stack implicitly.
>> 
>> Would this be true in any case of enumeration of the tree,
>> asuming that the stored structure has indeed the property of a
>> tree? 
> 
> I don't understand your question.

I know of at least one algorithm where it was necessary to peek down 
into the stack. This is not possible, if the stack is stored 
implicitely. Therefore the assumed benefit may turn out as a waste of 
space.