iteratee Fwd: [Haskell-cafe] Re: Fwd: Semantics of s, enumerators, enumeratees?

[Conal Elliott]

Oops.  I'd forgotten to CC the iteratee list.

---------- Forwarded message ----------
From: Conal Elliott <conal at conal.net>
Date: Tue, Aug 24, 2010 at 1:22 PM
Subject: Re: [Haskell-cafe] Re: Fwd: Semantics of iteratees, enumerators,
enumeratees?
To: Heinrich Apfelmus <apfelmus at quantentunnel.de>
Cc: haskell-cafe at haskell.org


I have omitted the chunking [Char] because I don't like it; invariance with
> respect to the chunk sizes is something that should be left to the iteratee
> abstraction.
>

I have this same reservation about iteratees.  And related one for
enumerators and enumeratees.  Assuming my sense of their intended meanings
is on track, they allow lots of well-typed but bogus values.

Defining and adhering to a precise denotational model would eliminate all of
these abstraction leaks, as Luke Palmer alludes to in
http://lukepalmer.wordpress.com/2008/07/18/semantic-design/ .

  - Conal


On Mon, Aug 23, 2010 at 4:06 PM, Heinrich Apfelmus <
apfelmus at quantentunnel.de> wrote:

> Conal Elliott wrote:
>
>> For anyone interested in iteratees (etc) and not yet on the iteratees
>> mailing list.
>>
>> I'm asking about what iteratees *mean* (denote), independent of the
>> various
>> implementations.  My original note (also at the end below):
>>
>
> In my world view, iteratees are just a monad M with a single operation
>
>    symbol :: M Char
>
> that reads the next symbol from an input stream. In other words, they're a
> very simple parser monad. The emphasis is not on parsing, but on the fact
> that one and the same monadic value can be run on different streams
>
>    runHandle     :: M a -> Handle -> IO a
>    runString     :: M a -> String -> a
>    runByteString :: M a -> ByteString -> a
>
> The monad M may also include convenience like exceptions and  liftIO .
>
> I have omitted the chunking [Char] because I don't like it; invariance with
> respect to the chunk sizes is something that should be left to the iteratee
> abstraction.
>
>
> Regards,
> Heinrich Apfelmus
>
> --
> http://apfelmus.nfshost.com
>
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