Syntax decision

[Ali Ebrahimi]

Hi,
I think with great support for type inference the need for casting lambas
(unless for disambiguating overloaded methods,... ) would be low.
And this ambiguity can be solved by applying some precedence in favor of
lambdas or versa.

Best Regards.

On Wed, Sep 28, 2011 at 6:11 PM, Brian Goetz <brian.goetz at oracle.com> wrote:

> The nilary syntax is still a thorn.  But the obvious solution outlined
> below -- allow elision of the () -- leads to a syntactic ambiguity.  If
> -> { statement; } were a valid lambda, then is:
>
>   (identifier) -> { statement; }
>
> a one-arg lambda with inferred type, or a cast of a nilary lambda?
>
> If people have brilliant other suggestions for nilary lambda syntax,
> we'd consider it.
>
>
>
> On 9/28/2011 2:03 AM, Howard Lovatt wrote:
> > Personally I am glad you have decided to go with -> since I have had
> > trouble reading Scala code, however this is not my main point in this
> > post which is have you decided if you require () for no arguments or if
> > you plan to allow a 'naked' -> e.g.:
> >
> > shortCutAnd( -> size >= 0, -> size < max ); // Example equivalent
> > to size >= 0 && size < max, but user written
> >
> > On 28 September 2011 05:18, Brian Goetz <brian.goetz at oracle.com
> > <mailto:brian.goetz at oracle.com>> wrote:
> >
> >     Update on syntax: the EG has chosen to stick with the -> form of the
> >     arrow that the prototype currently uses, rather than adopt the =>.
> >
> >     You could think of this in two ways (I'm sure I'll hear both):
> >
> >       - This is much better, as it avoids some really bad interactions
> with
> >     existing operators, such as:
> >
> >         x => x.age <= 0;                 // duelling arrows
> >     or
> >         Predicate p = x => x.size == 0;  // duelling equals
> >
> >       - What a bunch of idiots we are, in that we claimed the goal of
> doing
> >     what other languages did, and then made gratuitous changes "just for
> the
> >     sake of doing something different".
> >
> >     Obviously we don't think we're idiots, but everyone can have an
> >     opinion :)
> >
> >     In the end, this was viewed as a small tweak to avoid some
> undesirable
> >     interactions, while preserving the overall goal of "mostly looks like
> >     what lambdas look like in other similar languages."
> >
> >
> >
> >     On 9/8/2011 4:07 PM, Brian Goetz wrote:
> >      > This just in: the EG has (mostly) made a decision on syntax.
> >      >
> >      > After considering a number of alternatives, we decided to
> essentially
> >      > adopt the C# syntax.  We may still deliberate further on the fine
> >     points
> >      > (e.g., thin arrow vs fat arrow, special nilary form, etc), and
> >     have not
> >      > yet come to a decision on method reference syntax.
> >      >
> >      > The C# syntax is:
> >      >
> >      >     lambda = ArgList Arrow Body
> >      >     ArgList = Identifier
> >      >               | "(" Identifier [ "," Identifier ]* ")"
> >      >               | "(" Type Identifier [ "," Type Identifier ]* ")"
> >      >     Body = Expression
> >      >               | "{" [ Statement ";" ]+ "}"
> >      >
> >      > Here are some examples of lambda expressions using this syntax:
> >      >
> >      >     x =>  x + 1
> >      >     (x) =>  x + 1
> >      >     (int x) =>  x + 1
> >      >     (int x, int y) =>  x + y
> >      >     (x, y) =>  x + y
> >      >     (x, y) =>  { System.out.printf("%d + %d = %d%n", x, y, x+y); }
> >      >     () =>  { System.out.println("I am a Runnable"); }
> >      >
> >      > The decision to choose this syntax was twofold:
> >      >    - The syntax scores "pretty well" on most subjective measures
> >     (though
> >      > has cases where it looks bad, just like all the others do).  In
> >      > particular, it does well with "small" lambdas that are used as
> method
> >      > arguments (a common case), and also does well with large
> >      > (multi-statement) lambdas.
> >      >
> >      >    - Despite extensive searching, there was no clear winner among
> the
> >      > alternatives (each form had some good aspects and some really not
> >     very
> >      > good aspects, and there was no form that was clearly better than
> the
> >      > others).  So, we felt that it was better to choose something that
> has
> >      > already been shown to work well in the two languages that are
> >     most like
> >      > Java -- C# and Scala -- rather than to invent something new.
> >      >
> >      > A compiler implementation should be available soon.
> >      >
> >      >
> >      >
> >
> >
> >
> >
> > --
> >    -- Howard.
> >
>
>