foreach/opApply

[Christopher Wright]

Steve Teale wrote:
> The class need not contain an aggregate. The values iterated can be calculated in opApply from other class members, though there should be a corresponding class member  because of the ref in dg.

It could correspond to a local variable instead.

However, I'm curious about this: why is it that opApply must take a 
delegate with ref parameters? This doesn't make sense in many 
situations. I'm calculating values on the fly, and I can't go back if 
you decrement the index; the data I am passing is immutable (or at least 
in the text segment of the binary, which is protected as readonly and 
will segfault if you try writing to it). But I still need to pass by 
reference.

So, why? It didn't always work like that.