On Sat, Dec 24, 2011 at 10:49 PM, Dan Doel <dan.d...@gmail.com> wrote:
> On Sat, Dec 24, 2011 at 2:31 AM, Albert Y. C. Lai <tre...@vex.net> wrote: > > 1. a function f is strict if f ⊥ = ⊥ > > 2. ⊥ represents any computation which does not terminate, i.e. an > exception > > or an infinite loop > > 3. "strict" describes the denotational semantics > > All three of these statements are true. The only potentially > controversial one is 2, but any term that the operational semantics > would identify as simple non-termination (which is invariably what > they're talking about when they say 2; not some partially defined > term) will be given denotation ⊥. > > > B. Actually there are more, but apparently two is already enough to cause > > all kinds of incoherent statements. If I draw your attention to algebraic > > semantics, will you start saying "it is too lazy, need to make it more > > idempotent"? > > Yes, there are more than two. And they don't exist in completely > separate vacuums from one another. Denotational and operational > properties are sometimes (often?) correlated. And algebraic semantics > is often the sweet spot for reasoning about the structure of the > operational or denotational semantics of your code, without bringing > in all the irrelevant details from the latter two. I can make a > denotational semantics for System F where each term is denoted by its > normal form (an operational concept). > > I think it's good to be clear on all these specifics, and people could > do with a better recognition of the difference between (non-)strict > and (lazy)eager (hint: you can have an eager, non-strict language). > Can you elaborate? That's apparently my blind spot. > But it isn't necessarily a problem that people speak in terms of more > than one at once. The different kinds of semantics aren't in conflict > with one another. > > The main problem would be that such casual mixing prevents newcomers > from learning the distinctions by osmosis. > > -- Dan > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/
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