[Haskell-cafe] Closed Classes

[ajb at spamcop.net]

G'day all.

Quoting camarao at dcc.ufmg.br:

> Informally, what I see as the defining rule for "closed world" is: "an
> expression is typed according to the set of definitions that are
> visible in the context in which it is used".  Other possibilities
> exist, but the nice thing about this is that it is an extension of
> what happens without overloading.

Except that you can choose to export or not export a non-overloaded
function from a module, but you don't have that choice with typeclass
instances.

Cheers,
Andrew Bromage