Y combinator using lambda and method references

[Arul Dhesiaseelan]

Ah, that makes sense, it was just curiosity rather than application. Thanks
Brian for the cooler version of YC.

On Sat, Oct 27, 2012 at 11:55 AM, Brian Goetz <brian.goetz at oracle.com>wrote:

> The inference rules are still under development so it is not surprising
> that the IDE and the static compiler do not yet agree.  When the spec
> settles, hopefully both will agree :)
>
>
> On 10/27/2012 5:20 PM, Arul Dhesiaseelan wrote:
>
>> I attempted to port this Y combinator [1] using Java 8 lambdas. The
>> closest
>> I can make it work is shown here [2].
>>
>> It looks like intellij code inspection suggests I can still reduce this
>> further by using 2 method references and 1 lambda as shown visually here
>> [3], but I run into problems with those conversions.
>>
>> # 1 Applying the first inspection (line # 19) to a method reference fails
>> in a compile error:
>> error: cannot find symbol variable f
>>
>> #2 Applying the second inspection (line # 22) to a method reference
>> compiles just fine, but runs into a StackOverflowError. May be this is a
>> problem with the code itself.
>>
>> #3 Applying the third inspection (line # 31) to a lambda fails in a
>> compile
>> error:
>>
>> error: method Y in class YFact cannot be applied to given types;
>> required: Func<Func<T>>
>> found: (final Fun[...] - 1)
>> reason: cyclic inference - cannot infer target type for given
>> lambda/method
>> reference expression
>> where T is a type-variable:
>> T extends Object declared in method <T>Y(Func<Func<T>>)
>>
>> I am not sure if this is a case where the editor is incorrect in detecting
>> compilation errors. I believe the editor should reject these if the
>> compiler cannot infer the target type.
>>
>> Please apologize if this does not belong here.
>>
>> - Arul
>>
>> [1] http://www.arcfn.com/2009/03/**y-combinator-in-arc-and-java.**html<http://www.arcfn.com/2009/03/y-combinator-in-arc-and-java.html>
>> [2] https://gist.github.com/**3965968 <https://gist.github.com/3965968>
>> [3] https://dl.dropbox.com/u/**3274664/java/yfact-idea-**inspections.png<https://dl.dropbox.com/u/3274664/java/yfact-idea-inspections.png>
>>
>>