foreach, an analogy

[Walter Bright]

Gregor Richards wrote:
> The bigger door is 'for'.  'foreach' is nothing but a convenient wrapper 
> around 'for'.  And don't you OOphiles go telling me that your fancy 
> class foo that has iteration /needs/ 'foreach':
>   for (auto bar = foo.begin(); !(bar is null); bar = foo.iterate(bar))
> Is it less pretty than foreach?  Yeah.  That's why foreach exists.  But 
> don't go saying that the reverse foreach is a band-aid patch, because 
> both forms are just convenience wrappers around the far more powerful 
> and useful 'for'.

The C++ iterator approach has a serious problem: collections need to be 
linearized. This is not reasonable for some types of collections, such 
as a binary tree, which really wants to be traversed in a recursive 
descent fashion, rather than linearly.