[Haskell-cafe] Passing types as arguments

[ajb at spamcop.net]

G'day everyone.

Some time ago a suggestion came up about passing types as arguments
to functions:

    http://www.haskell.org/pipermail/haskell/2003-June/012184.html

As a matter of curiosity, the topic has come up again on the wiki:

    http://haskell.org/hawiki/StudyGroup/GraphExamplesInHaskell/WhySum3

For this example, we don't just want to pass types, we also want to
pattern match on them.

I'm curious if anyone else has put any thought to this idea.  Is it just
a syntax issue, or are there bad interactions with other parts of the
type system?

Cheers,
Andrew Bromage