struct vs. class

[Martin]

David B. Held Wrote:

> Martin wrote:
> > Inspired by the recent discussion about iterator structs/classes I wanted
> > to ask - what's the design rationale behind having both structs and classes?
> > [...]
> 
> The most important difference is that structs have value semantics and 
> classes have reference semantics.  There are very good reasons to have 
> both, and unifying them would be as wrong as taking away pointers or 
> taking away stack objects.

I totally agree that both are needed, but is it necessary to tie the difference to the difference between structs and classes? It would be nice if I could decide on the spot (i.e. when declaring a variable) in which way to use my type.