[Haskell-cafe] curious about sum

[Keith Sheppard]

I don't think anyone is calling it useless at this point. I could not
see a use for it initially and it was quickly pointed out that there
are in fact some infrequent use cases where a lazy sum is the best
option. I think this is more a discussion about "principle of least
surprise" or which use case is most frequent.

I am pretty new to haskell so I may just be missing something basic (I
welcome an explaination for why I am looking at this the wrong way),
but if your argument is on consistency then doesn't it follow that
number litterals should be defined using a church encoding or some
equivalent?

-Keith

On Thu, Jun 18, 2009 at 7:53 AM, Thomas Davie<tom.davie at gmail.com> wrote:
> No, I think it's extremely useful.  It highlights that numbers can both be
> lazy and strict, and that the so called "useless" lazy sum, is in fact,
> useful.
>
> Bob
>
> On 18 Jun 2009, at 13:29, Keith Sheppard wrote:
>
>> OK, I think I went off on a tangent that isn't very useful anyway
>>
>> thanks
>> -Keith
>>
>> On Wed, Jun 17, 2009 at 6:32 PM, Lennart
>> Augustsson<lennart at augustsson.net> wrote:
>>>
>>> The creators of Haskell didn't pick any particular representation for
>>> numbers.
>>> (Well, literals are kind of In..tegers.)  You can pick what types you
>>> make instances of Num.
>>> Some of them are lazy, some of them are strict.
>>>
>>> On Wed, Jun 17, 2009 at 11:05 PM, Keith Sheppard<keithshep at gmail.com>
>>> wrote:
>>>>
>>>> In lambda calculus numbers are just functions and you evaluate them
>>>> just like any other function. Haskell could have chosen the same
>>>> representation for numbers and all evaluation on numbers would be lazy
>>>> (assuming normal order evaluation). I think that would have been the
>>>> "Purist Lazy" way to go. That is not the way the creators of Haskell
>>>> designed language though... am i missing something?
>>>>
>>>> On Wed, Jun 17, 2009 at 4:05 PM, Lennart
>>>> Augustsson<lennart at augustsson.net> wrote:
>>>>>
>>>>> What do you mean by "literals are strict"?  Strictness is a semantic
>>>>> property of functions, and while literals can be overloaded to be
>>>>> functions I don't know what you mean.
>>>>>
>>>>> On Wed, Jun 17, 2009 at 9:50 PM, Keith Sheppard<keithshep at gmail.com>
>>>>> wrote:
>>>>>>
>>>>>> Haskell's numeric literals are strict. You wouldn't want that to
>>>>>> change right? It seems to me that having sum and product be strict is
>>>>>> consistent with this.
>>>>>>
>>>>>> -Keith
>>>>>>
>>>>>> On Wed, Jun 17, 2009 at 11:15 AM, Thomas Davie<tom.davie at gmail.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> On 17 Jun 2009, at 13:32, Yitzchak Gale wrote:
>>>>>>>
>>>>>>>> Henk-Jan van Tuyl wrote:
>>>>>>>>>
>>>>>>>>> reverse
>>>>>>>>> maximum
>>>>>>>>> minimum
>>>>>>>>
>>>>>>>> Oh yes, please fix those also!
>>>>>>>
>>>>>>> import Prelude.Strict?
>>>>>>>
>>>>>>> Honestly, these functions are ones that I've *deffinately* used lazy
>>>>>>> versions of, in fact, in the cases of minimum/maximum I've even used
>>>>>>> ones
>>>>>>> that are super-lazy and parallel using unamb.
>>>>>>>
>>>>>>> It would be extremely odd to randomly decide "most people would want
>>>>>>> this to
>>>>>>> be strict" based on no knowledge of what they're actually doing.
>>>>>>>  Instead,
>>>>>>> why don't we stand by the fact that haskell is a lazy language, and
>>>>>>> that the
>>>>>>> functions we get by default are lazy, and then write a strict prelude
>>>>>>> as I
>>>>>>> suggest above to complement the lazy version.
>>>>>>>
>>>>>>> Bob
>>>>>>> _______________________________________________
>>>>>>> Haskell-Cafe mailing list
>>>>>>> Haskell-Cafe at haskell.org
>>>>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> keithsheppard.name
>>>>>> _______________________________________________
>>>>>> Haskell-Cafe mailing list
>>>>>> Haskell-Cafe at haskell.org
>>>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>>>>
>>>>>
>>>>
>>>>
>>>>
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>>>
>>
>>
>>
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