[Haskell-cafe] Application of iterate

[Vincent Kraeutler]

Henning Thielemann wrote:
> On Fri, 23 Mar 2007, Neil Mitchell wrote:
>
>   
>>> my_sqrt t = last (take 20 (iterate (\n -> n/2 + t/(2 * n)) t))
>>>       
>
> http://darcs.haskell.org/htam/src/Numerics/ZeroFinder/Newton.hs
>
> with
>   inverse t (\x->(x^2,2*x)) t
>
>   
>>
>> I don't know how to add it into the one liner though - although I
>> suspect someone here will :)
>>     
>
>
> http://darcs.haskell.org/htam/src/Numerics/Sequence.hs
>
> limitDifference :: (Real a) => a -> [a] -> a
> limitDifference tol xs =
>    case dropWhile ((> tol) . abs . uncurry (-)) $ zip xs (tail xs) of
>       ((_,x):_) -> x
>       [] -> error "limitDifference: Finite sequence, but no element satisfies abort criterion."
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>
>   
as a fellow haskell newbie, i would like to take this opportunity to
encourage library authors to submit their material to the haskell hackage.

the haskell infrastructure is rather big, complex and "organic". (see
e.g. http://darcs.haskell.org/tmp/ for an example) it was only by chance
that i ran across the (rather amazing) htam library a week ago or so. i
hope you agree that these things should not be left to chance ;-)

hoogle, google and hackage tend to be the first places where i look for
fresh meat. i suppose this also applies to other haskell freshmen.

cheers,
v.

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