[Haskell-cafe] pure programs

Jamie Brandon 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
(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 <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.
> --
> _jsn
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