What is Expressiveness in a Computer Language

[David Hopwood]

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?

In a statically typed language that has a "dynamic" type, all
dynamically typed programs are straightforwardly expressible.

In a statically typed, Turing-complete language that does not have a
"dynamic" type, it is always *possible* to express a dynamically typed
program, but this may require a global transformation of the program
or use of an interpreter -- i.e. the "Felleisen expressiveness" of the
language is reduced.

-- 
David Hopwood <david.nospam.hopwood at blueyonder.co.uk>