[Haskell-cafe] Other instances of Integral
Eugene Kirpichov
ekirpichov at gmail.com
Fri Nov 27 09:00:11 EST 2009
I have not understood what the question is. Are you asking "Why would
one need functions of the form (Integral a) => ...a... if one can just
use ...Integer... or ...Int... explicitly"?
2009/11/27 Tsunkiet Man <temp.tsun at gmail.com>:
> 2009/11/27 Miguel Mitrofanov <miguelimo38 at yandex.ru>
>>
>>
>> Tsunkiet Man wrote:
>>>
>>> Hello,
>>> I would like to ask wheter there are other instances of the class
>>> Integral?
>>
>> Lots of them. You can define a few of them yourself, you know.
>
> Yes, I knew that =).
>>
>>> And I would like to ask what the difference is between the following
>>> functions: SomeFunctionA :: (Integral a) => a -> a,
>>
>> Perfectly correct.
>>
>>> SomeFunctionB (Integer a) => a -> a, SomeFunctionC (Int a) => a -> a.
>>
>> Both incorrect.
>>
>> Integral is a class, but Integer and Int are types.
>>
>>> What I do know is, that the Int can have underflow and overflows, however
>>> I don't actually see the difference (and I can't really find a difference on
>>> Google as it gives me results that aren't really relevant to my question)
>>> between prefering to use an Integral a when I've already got an Integer.
>>
>> Sorry, didn't understand your question.
>
> Was not really a question ^_^
>>
>>
>>>
>>> (Assuming I didn't missed the definiton of a Integral, which has by
>>> definition (I looked it up on Google:
>>> http://www.zvon.org/other/haskell/Outputprelude/Integral_c.html) has two
>>> instances)
>>
>> No. It makes no sense to say "by definition ... has that number of
>> instances". Instances of class are not included in it's definition and could
>> be defined separately.
>
> Ah I see!
>>
>>> Can someone explain to me what kind of advantages and disadvantages I
>>> would get when substituting SomeFunctionB for someFunctionA?
>>
>> Working program would certainly be an advantage.
>
>
>>
>> What if it both works? Should I take the "highest level"?
>>>
>>> Thank you for your help!
>>>
>>>
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>>>
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>
> This is actually all related to my homework problem which I can't seem to
> get a usefull answer out. Cause it tells me that a definition with Integrals
> would be much more general. It can support other instances of the class
> Integral. And then it asks me what the difference the definition has,
> actually it has none. Because I only use functions in de Prelude that are
> defined for Integrals.
>
> Correct me if I'm wrong with this =).
>
> I don't really understand how I should answer this homework question as it
> makes no sense in my opinion give me the answer and then asking me the
> question xD.
>
> Thanks for your quick response!
>
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>
--
Eugene Kirpichov
Web IR developer, market.yandex.ru
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