For anyone interested in iteratees (etc) and not yet on the iteratees mailing list.<br><br>I'm asking about what iteratees *mean* (denote), independent of the various implementations. My original note (also at the end below):<br>
<br><blockquote style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;" class="gmail_quote">With the encouragement & help of Conrad Parker, I've been looking at
iteratees, enumerators, enumeratees. I can find plenty written about
them, but only about benefits and implementation. In sifting through
chunks, error/control messages, and continuations, I find myself longing
for a precise semantic basis. I keep wondering: what simpler &
precise semantic notions do these mechanisms implement? Has anyone
worked out a denotational semantics for iteratees, enumerators,
enumeratees -- something that simplifies away the performance advantages
& complexities? I've worked out something tentative, but perhaps
I'm covering old ground.<br></blockquote><div><br> - Conal <br></div><br><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Conal Elliott</b> <span dir="ltr"><<a href="mailto:conal@conal.net">conal@conal.net</a>></span><br>
Date: Sun, Aug 22, 2010 at 11:02 PM<br>Subject: Re: Semantics of iteratees, enumerators, enumeratees?<br>To: John Lato <<a href="mailto:jwlato@gmail.com">jwlato@gmail.com</a>><br><br><br>Hi John,<br><br>I just remembered: Luke Palmer wrote an accessible & helpful description of this approach to library design. See his post <i><a href="http://lukepalmer.wordpress.com/2008/07/18/semantic-design/" target="_blank">Semantic Design</a></i>.<br>
<br>
(I've switched to using the more specific term "denotational design",
since I specifically intend denotational semantics, not operational.)<br><br>Denotational design is at the heart of most of what I do, particularly including the three pieces of work you mentioned: functional images (Pan), FRP, and automatic differentiation.<br>
<br>My main goal is simplicity with precision. Without the precision, I can't tell whether the simplicity is real or illusory.<br><br>We functional programmers have a strong advantage over imperative programming (including OO) in that we can achieve semantic precision. I want to see us exploit this advantage! And not settle for being a power tool for generating semantically inscrutable imperative computations.<br>
<br>Regards,<br><font color="#888888">
<br>
- Conal</font><div><div></div><div class="h5"><br><br><div class="gmail_quote">On Sun, Aug 22, 2010 at 10:43 PM, John Lato <span dir="ltr"><<a href="mailto:jwlato@gmail.com" target="_blank">jwlato@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Hi Conal,<br><br>I've always regarded your work in essentially the same category as Edward Kmett's (and most of Oleg's): stuff that's incredible powerful and concise, but I can't understand at all what it means. I've admired a lot of your work, particularly on Pan, FRP, and automatic differentiation, but most of the rest I couldn't understand at all.<br>
<br>I'll take a look at your <i>Denotational Design</i> paper again; maybe now that I have a lot more experience I'll be able to make sense of it.<br><font color="#888888"><br>John</font><div><div></div><div>
<br><br><div class="gmail_quote">On Sun, Aug 22, 2010 at 8:18 AM, Conal Elliott <span dir="ltr"><<a href="mailto:conal@conal.net" target="_blank">conal@conal.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi John,<br><br>Thanks for the reply. A denotational semantics would be independent of any implementation, so it would apply to any of them, as long as they have the same programming interface. The purpose is to simply & precisely say what the types and their building blocks (API) mean by providing a precise, implementation-independent, and simple-as-possible math model. Such a semantics can be used to prove properties and to define correctness of any implementation. It also gives clear feedback on how elegant or inelegant a library design is.<br>
<br>For instance, given a type, Map k v, of finite maps, we might say the meaning is the type of partial functions from k to v, either k -> v (where absent is _|_) or k -> Maybe v (where absent is Nothing). Then we'd give the meaning of each Map operation as a function of the meanings of its arguments. This example and several others are given in the paper <i><a href="http://conal.net/papers/type-class-morphisms/" target="_blank">Denotational design with type class morphisms</a></i>.<br>
<br>Regards, - Conal<br><br><div class="gmail_quote">On Sun, Aug 22, 2010 at 8:31 PM, John Lato <span dir="ltr"><<a href="mailto:jwlato@gmail.com" target="_blank">jwlato@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Hi Conal,<br><br>To my knowledge, nobody has attempted this. Oleg may have some ideas, but I don't think he's written about it. I really don't know anything about denotational semantics, so I couldn't do this myself. For some time I've thought it would be good if somebody were able to put together a formal semantics for iteratees, so I'd be very interested if you'd share what you have so far.<br>
<br>Would a denotational semantics apply equally to multiple implementations, or would it be tied to a specific implementation?<br><br>John<br><br><div class="gmail_quote">On Sun, Aug 22, 2010 at 3:47 AM, Conal Elliott <span dir="ltr"><<a href="mailto:conal@conal.net" target="_blank">conal@conal.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">With the encouragement & help of Conrad Parker, I've been looking at iteratees, enumerators, enumeratees. I can find plenty written about them, but only about benefits and implementation. In sifting through chunks, error/control messages, and continuations, I find myself longing for a precise semantic basis. I keep wondering: what simpler & precise semantic notions do these mechanisms implement? Has anyone worked out a denotational semantics for iteratees, enumerators, enumeratees -- something that simplifies away the performance advantages & complexities? I've worked out something tentative, but perhaps I'm covering old ground.<br>
<font color="#888888">
<br> - Conal<br>
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