[Haskell-cafe] Re: ANN: Data.Stream 0.4

[Heinrich Apfelmus]

Bas van Dijk wrote:
> 1) What's the difference between your:
> "tail ~(Cons _ xs) = xs"
> and the more simple:
> "tailStrict (Cons _ xs) = xs" ?
> 
> I know they're desugared to:
> "tail ys = let Cons _ xs = ys in xs"
> and:
> "tailStrict ys = case ys of Cons _ xs -> xs" respectively.
> 
> But aren't they operationally the same:
> 
> "tail undefined = undefined"
> and:
> "tailStrict undefined = undefined"

I concur, a strict  tail  is enough. Writing

   foo xs = bar (tail xs)

has the same effect as

   foo xs = bar (tailStrict xs)

since the evaluation of  xs  is deferred in both cases.


Regards,
apfelmus

--
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