[Haskell-beginners] what space leak could happen here?

[Dimitri DeFigueiredo]

Thanks!

I don't quite understand the last sentence, though. So, it is a leak 
just because it needs to evaluate an element that may not be required? I 
thought a space leak implied we would be changing the "Big O" asymptotic 
order of space usage. How would the extra evaluation would change that?

Thanks again,

Dimitri

On 21/09/14 13:20, Chaddaï Fouché wrote:
> On Sun, Sep 21, 2014 at 7:05 PM, Dimitri DeFigueiredo 
> <defigueiredo at ucdavis.edu <mailto:defigueiredo at ucdavis.edu>> wrote:
>
>     I don't understand why we need to "make every element in the
>     'intersperse'd list available as soon as possible to avoid space
>     leaks." Could somebody shed some light on what could cause a space
>     leak here? In particular, would this simpler version cause problems?
>
>
> This is delicate but basically your version needs to force the second 
> element of the list (to check if it's []) before it produce the first 
> element of the result while the base version doesn't, check with "take 
> 1 . intersperse ',' $ 'a' : undefined".
>
> The leak can occur when you only need the first element of the result 
> to start producing but the second one is expensive to produce and 
> store, the base version avoid the problem by being maximally lazy.
> -- 
> Jedaï
>
>
>
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