Why no list heritable type?

[James Stroud]

Steve Holden wrote:

> I think the thing you are really missing is the fact that list and the 
> other built-in types can be used as the basis for inheritance:

I've never seen this done in any manual that I can remember. Its so useful, 
that I thought I would have run into it before as an example somewhere, so It 
didn't occur to me that it could be done (too good to be true, even though it 
is obvious, phenomenon), and I never tried it, already /knowing/ the answer.

Thanks everyone for your answers.

James