[Haskell-cafe] Re: Laws and partial values
lennart at augustsson.net
Sun Jan 25 12:45:21 EST 2009
If all tuples in Haskell were unlifted then () would not be such a special case.
But I would argue against unlifted tuples, because that would make
tuples (or single constructor data types) different from other data
types; adding a constructor to a type could totally wreck laziness of
a program with unlifted tuples.
Also, unlifted tuples forces parallel evaluation for seq.
On Sun, Jan 25, 2009 at 5:17 PM, Jonathan Cast
<jonathanccast at fastmail.fm> wrote:
> On Sun, 2009-01-25 at 09:04 -0800, Conal Elliott wrote:
>> On Sun, Jan 25, 2009 at 7:11 AM, Jonathan Cast
>> <jonathanccast at fastmail.fm> wrote:
>> On Sun, 2009-01-25 at 10:46 +0100, Thomas Davie wrote:
>> > On 25 Jan 2009, at 10:08, Daniel Fischer wrote:
>> > > Am Sonntag, 25. Januar 2009 00:55 schrieb Conal Elliott:
>> > >>> It's obvious because () is a defined value, while bottom
>> is not -
>> > >>> per
>> > >>> definitionem.
>> > >>
>> > >> I wonder if this argument is circular.
>> > >>
>> > >> I'm not aware of "defined" and "not defined" as more than
>> > >> terms.
>> > >
>> > > They are informal. I could've written one is a terminating
>> > > computation while
>> > > the other is not.
>> > Is that a problem when trying to find the least defined
>> element of a
>> > set of terminating computations?
>> Yes. If you've got a set of terminating computations, and it
>> multiple distinct elements, it generally doesn't *have* a
>> least element.
>> The P in CPO stands for Partial.
>> and this concern does not apply to () .
> And? () behaves in exactly the same fashion as every other Haskell data
> type in existence, and in consequence we're having an extended, not
> entirely coherent, discussion of how wonderful it would be if it was a
> quite inconsistent special case instead? Why?
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