You're essentially describing functional reactive programming. You end
up with the system being described as pure, reactive values and
plugging IO based streams in at the edges.
Have a look at the wiki description
(http://www.haskell.org/haskellwiki/Functional_Reactive_Programming)
and especially the Reactive library
(http://www.haskell.org/haskellwiki/Reactive).
Theres been a fair amount of work on using frp for distributed,
network-orientated systems. Flask
(http://portal.acm.org/citation.cfm?id=1411203.1411251) and Opis
(http://perso.eleves.bretagne.ens-cachan.fr/~dagand/opis/) are
particularly interesting. Opis really shows the value of using pure
functions by allowing the same reactive system to be run in
production, attached to a debugger, run in a step-by-step simulator or
run in a model checker without altering the systems code.
On Wed, Nov 5, 2008 at 12:12 AM, Jason Dusek
Informally, a "pure program" an executable such that the stream of bytes entering it totally determines the stream of bytes leaving it.
Many useful programs that I would like to write in Haskell don't fall into this category -- for example, network servers -- but a lot of their components do. Can these components can be Haskell functions without IO in their signatures?
Though that seems reasonable, it is not, in general, true. For example, System.Info.os is generally treated as pure, though it is not. It's not clear to me how to disambiguate these "born again" values from really pure values.
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