[scala] Eta expansion and function values

[Jesper Nordenberg]

The following came up after a discussion in the IRC channel:

List(Some(1), None) flatMap identity[Option[Int]]

works fine, but:

val id = identity[Option[Int]] _
List(Some(1), None) flatMap id

doesnt work. "(id(_))" works though.

I can understand the reason why this happens, but still I find it
confusing and inconsistent. Can the implicit conversion rules for
function values and eta expansion be made more consistent?

/Jesper Nordenberg

[tmorris]

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Jesper Nordenberg wrote:

> The following came up after a discussion in the IRC channel:
>
> List(Some(1), None) flatMap identity[Option[Int]]
>
> works fine, but:
>
> val id = identity[Option[Int]] _ List(Some(1), None) flatMap id
>
> doesnt work. "(id(_))" works though.
>
> I can understand the reason why this happens, but still I find it
> confusing and inconsistent. Can the implicit conversion rules for
> function values and eta expansion be made more consistent?
>
> /Jesper Nordenberg
>
>
>

Hi Jesper,
I was about to "WTF!? That shouldn't type-check!", then I realised
List.flatMap is broken. Maybe this has something to do with it. You
could write a repaired example for any difference perhaps?


- --
Tony Morris
http://tmorris.net/

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