State of the (Java) Lambda | Hacker News Reader

State of the (Java) Lambda

cr.openjdk.java.net

31 pointsgthank9 comments

Well, at the very least the new syntax is a tremendous improvement upon the previous proposals. (http://cr.openjdk.java.net/~mr/lambda/straw-man/)

Compare the old

  #(int x)(x + x)

To the new

  {x -> x + x}

Much more consistent with the syntax of normal Java. Seems to be borrowing from C#.

I hadn't followed up on it since the previous proposal but....thank goodness.

The pound-sign lambda annoyed me since other lambda capable languages use it to denote comments. It wasn't a dealbreaker, but it certainly was less than preferred.

I agree. I know of no other language where a # is used to denote lambdas. I would prefer one of:

1. a keyword such as fn, fun, function, lambda. (Incidently, my language uses fn)

2. {...} are used to denote code blocks in many languages, including Java

3. -> or => are also used for functions in several languages (IIRC C# uses =>)

# is used for lambda shorthand in Clojure. #(+ % %2) is shorthand for (fn [x y] (+ x y)).

That's a nice shorthand. AIUI, Arc uses [... _ ....] as a terse shorthand for closures, but can only deal with functions that take one argument that way -- though it would be simple to expand Arc so it could say [+ _ _2].

Now I've thought about it, I may add something similar as syntax in Unify: (tn + _ _2) (where tn stands for "terse function")

Is it still part of Java 7 release?

Instead of {x -> x + 1} you could always run clojure on your existing production JVM and write #(+ % 1) to get the same effect.

I find the use of "yield" a little strange. In Ruby yield, yields the execution to the block that was passed in as an argument to the method being invoked. In this proposal it would replace the "return" statement inside a lambda.

In other languages, yield is used for coroutine (continuation) return. Bad choice. There is actually no reason not to use return, or to disallow break and continue. These could all have the same meaning as they do in a SAM implemented with an inner class.

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