Hi Jason,
To help me understand your question, would you be unhappy with the following
structure?
-- runnable
main = interact f
-- composable
f = ...
The discipline is to use interact (or another combinator) to wrap a
functional/composable/pure component like f into an executable. Then give
main to users and f to programmers. This same game can be made more
sophisticated, eg
main = interact (show . f . read)
Or unparse & parse in place of show & read.
For more on combining usability and composability, see
http://haskell.org/haskellwiki/TV
http://conal.net/blog/posts/tangible-functional-programming-a-modern-marriage-of-usability-and-composability/
- Conal
On Tue, Nov 4, 2008 at 4:12 PM, Jason Dusek <[EMAIL PROTECTED]> 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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