Comments on JDK-8198408 please ?

Stephen Colebourne scolebourne at joda.org
Tue Feb 27 10:20:07 UTC 2018


On 26 February 2018 at 21:46, John Rose <john.r.rose at oracle.com> wrote:
> Even if we support single-level field assignment (as twisted sugar for
> withfield) we should *not* support multiple-level field assignment.
>
> In fact, I'm doubting (again, after several years) the wisdom of allowing
> even the single-level x.a = 11.  It seems to lead the user model into a
> swamp.  And also contains a paradox, that a subexpression on the LHS
> of an assignment gets modified, in addition to the whole LHS.

I think having a.x = 11 "modify" a would be a poor choice. My
preferred approach is something more like this:

 a = a.with(x = 11);

where multiple fields can be set:

 a = a.with(x = 11, y = 12);

And potentially this could be multi-level:

eg. instead of d.c.b.a.x = 11;

 d = d.with(c.b.a.x = 11);

No doubt the solution adopted for values would be similar to that for
records too.

Stephen


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