Re: Signature of Abstract Methods

On Wed, Aug 15, 2012 at 10:35 PM, Seyed H. HAERI (Hossein)
<hossein.haeri@...> wrote:
> Hi Alex,
>
>  > This is a method, which, when invoked, performs the computation,
> rather than returning a function value.
>
> I see.
>
>  > Methods can be turned into functions automatically (through eta
> expansion) but they're not equivalent.
>
> OK, then, I need to ask what functions are in Scala? I was always
> under the impressions that there are no free functions in Scala and
> all functions are methods. I seem to understand now that that's wrong.
> Would you mind correcting me?

You are mostly correct. Every code executed in Scala is inside a
method or a contructor, no exception. However, Scala hides this for
certain cases.

Specifically, there are traits called Function0 through Function22,
which implement the concept of a function as an object. Scala supports
them in various ways:

* The method "apply" can be omitted, so obj.apply(params) can be
written as obj(params)
* There's syntax for anonymous functions, so that, for example, "(x:
Int) => x * 2" automatically creates an instance of the trait
Function1 with an apply method implemented accordingly.