Updated State of the Lambda

[maurizio cimadamore]

  On 16/10/2010 06:36, Ali Ebrahimi wrote:
> looks fine. another step to real closures.
>
> but one question. if we can not improve the inference scheme to support
> following sample code?
>
Hi Ali
I think the new semantics of this is very polished and removes many 
complex interactions between the lambda body and the target type which, 
in turn should allow for better inference. That alone, however, won't be 
enough to make this example work. In this specific case I think that the 
inference changes required in order to make things work are deeper than 
it might seem - as I said in a related post, the problem with inference 
in chained method invocations _is_ a problem in the Java language as 
currently specified, regardless of lambda (i.e. you could write examples 
w/o lambda that exhibit the same problem). With lamba things get a lot 
worse since chained calls are very common in certain kinds of libraries, 
and of course we need a better inference story in order to allow that.

Maurizio
> public class Test
> {
>     public static class Customer {
>        public String getName() { return "";}
>     }
>     public abstract static class StringSorter<U>  {
>        abstract String value(U val);
>     }
>     public static interface Select<U, V>  {
>        public V select(U val);
>     }
>     public static class DBSet<T>   {
>        public<U>  DBSet<U>  select(Select<T,U>  x) {return new DBSet<U>();}
>        public DBSet<T>  sortedByStringAscending(StringSorter<T>  x) {return this;}
>     }
>
>     public static DBSet<Customer>  allCustomer()
>     {
>        return new DBSet<Customer>();
>     }
>
>     public static void main(String[] args)
>     {
>        DBSet<String>  result = allCustomer()   //DBSet<Customer>
>           .select(#{c ->  c.getName()})      // This line fails in compile time
>           .sortedByStringAscending(#{str ->  str});
>
>     }
> }
>
>
> On Fri, Oct 15, 2010 at 11:25 PM, Brian Goetz<brian.goetz at oracle.com>wrote:
>
>> An updated draft (Version 3) of the State of the Lambda has been published
>> at:
>>
>>    http://cr.openjdk.java.net/~briangoetz/lambda/lambda-state-3.html
>>
>> Notable differences from the previous draft include:
>>   - 'this' in lambda expressions is lexically scoped
>>   - 'yield' keyword dropped in favor of 'return'
>>   - new syntax
>>
>> Maurizio will be pushing an implementation conforming to this draft soon.
>>
>>
>>