[Haskell-cafe] pure programs
jamiiecb at googlemail.com
Tue Nov 4 19:26:56 EST 2008
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
and especially the Reactive library
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
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 <jason.dusek at gmail.com> wrote:
> 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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