[Haskell-cafe] list comprehension doesn't work

Daniel Díaz Casanueva dhelta.diaz at gmail.com
Tue May 14 17:24:44 CEST 2013


Well, definitely, isSqrt should be called isSquare.


On Tue, May 14, 2013 at 5:22 PM, Daniel Díaz Casanueva <
dhelta.diaz at gmail.com> wrote:

> You can always write it like this:
>
> listPairs = [ (x,y) | x <- [6 .. 499] ,  y <- [0 .. 1000] , isProduct x ,
> isSqrt y , mod y x == 0 ]
>
> So you have the bounds for x and y, and then the conditions. You then need
> to define isProduct and isSqrt with types
>
> isProduct :: Int -> Bool
> isSqrt :: Int -> Bool
>
> Hopefully, these problems will look easier separately.
>
> Well, it's just an idea.
>
> Good luck,
> Daniel Díaz.
>
>
> On Tue, May 14, 2013 at 4:57 PM, John <knowledge1202 at gmail.com> wrote:
>
>> Hi,
>>
>> I have to write a function which returns a list of all pairs (x,y) where
>> x,
>> y ∈ N AND:
>> –  x is the product of two natural numbers (x = a · b, where a, b ∈ N) AND
>> –  x is really bigger than 5 but really smaller than 500, AND
>> –  y is a squer number (y = c² where c ∈ N) NOT greater than 1000, AND
>> –  x is a divisor of y.
>>
>> My attempt is as follows:
>>
>> listPairs :: [(Int, Int)]
>> listPairs = [(x,y) | x<-[0..], y<-[0..], x<-[0..]*[0..], x > 5, x < 500,
>> (y*y) < 1001, mod y x == 0]
>>
>> However it doesn't work unfortunatly
>>
>> Could anyone tell me where my mistake is?
>>
>> Thanks.
>>
>>
>>
>> --
>> View this message in context:
>> http://haskell.1045720.n5.nabble.com/list-comprehension-doesn-t-work-tp5730158.html
>> Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
>>
>> _______________________________________________
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>
>
>
>
> --
> E-mail sent by Daniel Díaz Casanueva
>
> let f x = x in x
>



-- 
E-mail sent by Daniel Díaz Casanueva

let f x = x in x
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20130514/c6ba82fd/attachment.htm>


More information about the Haskell-Cafe mailing list