Proposal for a simplified syntax for invoking @FunctionalInterface methods

Christoph Engelbert me at noctarius.com
Thu Mar 23 14:01:49 UTC 2017


Hey guys,

Comments inline:

> On 23. Mar 2017, at 06:54, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
> 
> This is a question for lambda-dev.
> 
> Something like this was present in the very first draft of the lambda language support [1] - syntax aside, the main issue with this avenue, is that Java has separate namespaces for methods and fields. That is, you are able to declare a field AND a method whose type is 'doubleString'. So, if you start treating fields in a more method-y way, the namespace issue might pop up, and ambiguities might ensue.

But wouldn’t that just be another layer of name shadowing like we already have on fields? I think it’s all about precedence of field over method or method over field. Do I miss something here (I probably do :-))?

> 
> [1] - http://cr.openjdk.java.net/~mr/lambda/straw-man/
> 
> Maurizio
> 
> 
> On 02/03/17 15:10, Timothy Fagan wrote:
>> I'm not sure if this is the appropriate forum, or if this idea has been
>> proposed elsewhere, but I'd like to suggest a simplified syntax for
>> invoking @FunctionalInterface methods.
>> 
>> The idea is that if:
>> *  foo is a object reference (field, local variable or parameter) whose
>> type is a @FunctionalInterface
>> *  there is a statement or expression where foo is used as if it were a
>> method name
>> *  the formal parameters of the statement or expression match the formal
>> parameters of the abstract method on the @FunctionalInterface
>> *  the formal parameters of the statement or expression do NOT match the
>> formal parameters of any other method in scope named foo
>> Then:
>> *  the statement or expression is compiled as an invocation of the
>> @FunctionalInterface abstract method on foo's type.
>> 
>> E.g.
>> 
>> Function<String, String> doubleString = s -> s + s;
>> 
>> // prints "hellohello"
>> System.out.println(*doubleString*("hello"));
>> 
>> -Timothy
> 



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