What is Expressiveness in a Computer Language

[Joe Marshall]

QCD Apprentice wrote:
> Joe Marshall wrote:
> > Marshall wrote:
> >>
> >> The real question is, are there some programs that we
> >> can't write *at all* in a statically typed language, because
> >> they'll *never* be typable?
> >
> > Certainly!  As soon as you can reflect on the type system you can
> > construct programs that type-check iff they fail to type-check.
>
> Sorry, but can you elaborate on this last point a little?  I think I
> missed something.

This is just the halting problem lifted up into the type domain.