Updated State of the Lambda

[Brian Goetz]

Because it just doesn't carry its weight.  The alternate version you 
propose is one token shorter.  That would be adding incremental 
complexity for no incremental benefit.

If I had to guess, I would think what you're really getting at is that 
it is annoying to have to declare them as actual interfaces (and worse, 
one class per file), instead of as a local type alias of sorts in the 
class file that uses it.  Is that what you're getting at?



> What about defining a new syntax for declaring functional interfaces, so
> that the interface as well as its implementation can address the
> vertical problem? Something like:
>
>     interface MyComparable<T> = int compareTo(T other);
>
>
> Which would be equivalent to:
>
>     interface MyComparable<T> {
>          int compareTo(T other);
>     }
>
> Apologies if this is also covered ground. I searched for java + lambda
> [dev] + delegate, since this seems a bit similar to C#'s delegate syntax.
>
> On Fri, Dec 9, 2011 at 3:32 PM, Brian Goetz <brian.goetz at oracle.com
> <mailto:brian.goetz at oracle.com>> wrote:
>
>     Yes, this is well-covered ground.  What you're asking for is
>     "function types" (or arrow types, or algebraic function types, or
>     structural functions types.)  The short answer is "no".
>
>     Function types are the "obvious right way" to represent the type of
>     a lambda, until you realize that they will end up getting
>     implemented using generics, which means they will be erased.  Erased
>     function types are the worst of both worlds.
>
>     Instead, we use functional interfaces in APIs, and then users can
>     use named classes, anonymous classes, or lambdas to create instances
>     of the functional interfaces.
>
>
>
>     On 12/9/2011 1:44 PM, Yuval Shavit wrote:
>
>         By the way -- and I apologize if this has already been covered,
>         I did
>         some searching and nothing came up -- is there any thought as to
>         whether
>         methods will ever be able to declare lambdas as arguments?
>           Something like:
>
>             public <T> void myFilter(Iterable<? extends T>, (? super T ->
>             boolean) predicate ) { ... }
>
>
>         This function could then take either a lambda of the same type,
>         or any
>         reference typed as a functional interface which could be
>         expressed as a
>         corresponding lambda.
>
>         Thanks,
>         Yuval
>
>         On Fri, Dec 9, 2011 at 1:28 PM, Brian Goetz
>         <brian.goetz at oracle.com <mailto:brian.goetz at oracle.com>
>         <mailto:brian.goetz at oracle.com
>         <mailto:brian.goetz at oracle.com>__>> wrote:
>
>             An updated State of the Lambda is available here:
>
>         http://cr.openjdk.java.net/~__briangoetz/lambda/lambda-__state-4.html
>         <http://cr.openjdk.java.net/~briangoetz/lambda/lambda-state-4.html>
>
>
>
>