[Haskell-cafe] FP design

[Justin Bailey]

> So I'm the one user in a thousand that will want to provide my own I/O
> functions, for example.  In the old world, I guess I would be looking
> for some extended API where my I/O functions are parameters to the "open"
> or "init" function, and the IMAP functions take over from there.  In a
> more pure functional oriented model, could it be an extended API that
> exposes the IMAP functionality as operations on data, and leaves it to
> me to deal with the I/O?

I believe a typeclass could solve this for you. The typeclass member
functions serve as your interface definition. For example, say "auth"
was a member function. Then you could implement instances which
authorized using NTLM, HTTP Basic, etc.

It's similar to how you'd do the same thing in java with interfaces, in fact.

Justin