[Haskell-beginners] Function to compute the mean

[Tarik ÖZKANLI]

Hello,

In standard usage there is not much difference. But in Haskell, people
prefer to write in curried form (first implementation of yours) which has
the advantage of using partially applied form when suitable.

Regards.

Tarık Özkanlı


On Sat, 8 May 2021 at 12:43, Joe King <joeking1809 at yahoo.com> wrote:

> Greeetings I am new here and pretty new to Haskell.
>
> I was wondering what are the relative advanatges/disadvatnages of
> specifying a mean function in these two ways:
>
> mean :: [Double] -> Double
> mean xs = sum xs / fromIntegral (length xs)
>
> and
>
> mean1 :: (Real a, Fractional b) => [a] -> b
> mean1 xs = realToFrac (sum xs) / genericLength xs
>
> I understand that mean1 has the advantage that it can be called with lists
> of any Real type, so would work with things like
>
> foo :: [Int]
> foo = [1,2,3]
>
> mean foo
> -- type mismatch error
>
> mean1 foo
> -- no error
>
> But suppose that I know I will only ever use lists of Double, is there
> still any advantage (or disadvantage of using mean1). For example is there
> any performance benefit by using mean in that case since mean1 has
> additional function evaluation.
>
> Are there any other considerations ?
>
> Thanks in advance
> JK
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