Reified Lambda Functions

[Howard Lovatt]

Hi Neal,

Sorry for taking so long to reply, I was on holiday with limited
connectivity.

Yes there is a bug in the specification, I have updated section 2.1, 4.3.1,
4.3.2, 5.2.2, and 5.3.2 and added sections 4.4 and 5.4 - thanks. (At the
same time, but unrelated, I have added section 1.1 and changed the
topographical convention used, swapping the roles of _ and $.)

With the updated specification the reified lambdas are little different than
any other example with generics. Contrast:

  static <T> List<T>[] makeArrayOfList(final int size) { return
(List<T>[])new List[size]; }

  static void makeArrayOfStringListTest() {
    final List<String>[] arrayOfList = makeArrayOfList(1);
    arrayOfList[0] = new ArrayList(1);
    arrayOfList[0].add("Hello from a List");
    System.out.println("ArrayOfStringList(0) = " + arrayOfList[0].get(0));
  }

With:

  static <T> #T()[] makeArrayOfLambda0(final int size) { return #T()[size];
}

  static void makeArrayOfStringLambda0Test() {
    final #String()[] arrayOfLambda0 =
Examples.<String>makeArrayOfLambda0(1); // I doubt the type inference will
cope, hence qualification
    arrayOfLambda0[0] = #String() ("Hello from a Lambda0");
    System.out.println("ArrayOfStringLambda0[0].call() = " +
arrayOfLambda0[0].call());
  }

Which is translated to:

  static <T> _Callable_0<? extends T>[] makeArrayOfLambda0(final int size) {
return (_Callable_0<? extends T>[])new _Callable_0[size]; }

  static void makeArrayOfStringLambda0Test() {
    final _Callable_String[] arrayOfLambda0 =
_Array_From_0_String__To_String.instance(Examples.<String>makeArrayOfLambda0(1));
    arrayOfLambda0[0] = new _Callable_String() {
      @Override public String call() { return "Hello from a Lambda0"; }
    };
    System.out.println("ArrayOfStringLambda0[0].call() = " +
arrayOfLambda0[0].call());
  }

Thanks again for pointing out the problem,

 -- Howard.


2010/1/8 Neal Gafter <neal at gafter.com>

> On Fri, Jan 8, 2010 at 2:19 PM, Howard Lovatt <howard.lovatt at iee.org>
> wrote:
> > I am not sure what you have in mind, do you have an example I could try
> > coding up.
>
> <T> #T()[] makeArray(int size) {
>  return new #T()[size];
> }
>
> and a client
>
> #String()[] array = makeArray(20);
>
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-- 
 -- Howard.