first-class structures & existential types

[Fergus Henderson]

Hi,

Can anyone explain to me what "first class structures" are,
and how they differ from (or relate to) existential types?

-- 
Fergus Henderson <[EMAIL PROTECTED]>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger [EMAIL PROTECTED]         |     -- the last words of T. S. Garp.