Current State of Closures

[Dr Andrew John Hughes]

Will the following be possible now or in the future as part of Project Lambda?

public class TestClosures
{
  public static #Integer(Integer) partial(#Integer(Integer, Integer)
func, int arg1)
  {
    return func.(Integer.valueOf(arg1));
  }

  public static void main(String[] args)
  {
    #Integer(Integer,Integer) pow = #(Integer x, Integer y)(x * y);
    #Integer(Integer) part = partial(pow, 2);
    System.out.println(part.(2));
  }
}

i.e. being able to supply a partial set of arguments to a method so
that a new method is returned.

In Haskell,

> :t (\x -> \y -> x * y)
(\x -> \y -> x * y) :: (Num a) => a -> a -> a
> :t (\x -> \y -> x * y) 2
(\x -> \y -> x * y) 2 :: (Num a) => a -> a

Currently this gives:

TestClosures.java:5: lambda expression cannot be applied to given types
    return func.(Integer.valueOf(arg1));
                ^
  required: Integer,Integer
  found: Integer
-- 
Andrew :-)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

Support Free Java!
Contribute to GNU Classpath and the OpenJDK
http://www.gnu.org/software/classpath
http://openjdk.java.net

PGP Key: 94EFD9D8 (http://subkeys.pgp.net)
Fingerprint: F8EF F1EA 401E 2E60 15FA  7927 142C 2591 94EF D9D8