What is Expressiveness in a Computer Language

[Benjamin Franksen]

Pascal Costanza wrote:
> There is, of course, room for research on performing static type checks
> in a running system, for example immediately after or before a software
> update is applied, or maybe even on separate type checking on software
> increments such that guarantees for their composition can be derived.
> However, I am not aware of a lot of work in that area, maybe because the
> static typing community is too focused on compile-time issues.

Not everyone is. For instance, Don Stewart has been enormously successful in
deploying such a system for Haskell (very much a statically typed language)
in a practically usable way. It is called hs-plugins (see
http://www.cse.unsw.edu.au/~dons/hs-plugins/), a framework for run-time
loading and re-loading of Haskell modules (in source form or already
compiled, giving different levels of security). Far from being a purely
academic exercise, there are interesting applications, including yi, an
extensible editor, and lambdabot, an IRC bot, both available from the above
same home page.

Cheers,
Ben