[Haskell-beginners] Square root algorithm

[PATRICK BROWNE]

Why is it the sqrt0 function is so much slower than sqrt1. Does the where
clause allow intermediate values to be stored?
Regards,
Pat
sqrt0 :: Int -> Int
sqrt0 0 =  0
sqrt0 1 =  1
sqrt0 n =   ((sqrt0 (n - 1)) + (n `quot` sqrt0 (n-1))) `quot` 2
-- sqrt0 25 several minutes
sqrt1 :: Int -> Int
sqrt1 n
 | n ==  0              = 0
 | n ==  1              = 1
 | otherwise            = div (k + ( div n k)) 2
 where k = sqrt1(n-1)
-- sqrt1 25 instant


On 9 September 2017 at 05:49, KC <kc1956 at gmail.com> wrote:

> One approach
>
> One function to compute the next iterate
>
> Another function to call the computation function until results are within
> some tolerance
>
> It's usually presented as separation of control and computation 😎
>
> --
> Sent from an expensive device which will be obsolete in a few months
> Casey
>
> On Sep 3, 2017 1:23 AM, "mike h" <mike_k_houghton at yahoo.co.uk> wrote:
>
>> Hi,
>>
>> To help me in learning Haskell I started blogging about some of the
>> things I’ve looked at.
>> One such topic was calculating square roots ‘by hand’ and then deriving a
>> Haskell algorithm.
>> I wrote about the well known  technique here
>> http://gitcommit.co.uk/2017/08/25/the-root-of-the-problem-part-1/
>>
>> and it it is really quite a simple method.
>>
>> The second part of the post will be an implementation in Haskell.
>>
>> I then tried implementing it  and got something that works but really its
>> not very pleasant to look at! And its something I don’t want to post! Some
>> parts are fine but I think I locked myself into the notion that it had to
>> be using State and  really the end result is pretty poor.
>>
>> I know this i perhaps a ‘big ask’ but I’d really appreciate any
>> suggestions, solutions, hints etc. I will of course give full attribution.
>>
>> I’ve created a gist of the code here
>> https://gist.github.com/banditpig
>>
>> Many Thanks
>>
>> Mike
>>
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>>
>>
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