'Equals' in any-typed code: VERY BIG PROPOSAL

Thomas W twhitmore.nz at gmail.com
Thu Jan 8 04:58:05 UTC 2015


Hi Vitaly,

Thanks for your interest in this area.

> Why do you need language feature for #2? What's wrong with calling a lib
> method that wraps this up for you?

Collections are built on 'eq' and 'hashCode'. It's a fundamental basic
operator on values, and we're now moving to support values. So, change is
here & we have an opportunity to get it right.

You are correct, a static helper/ or EqualsStrategy can also achieve this
for collections.

But for the language more widely & application programming in general, an
'eq' operator would be a great help. As well as being a very simple & clean
solution for specializable Collections.

Here's a demonstration of length:

    if (car.getColor() != null && car.getColor().equals( someColor))) {
    if (ObjectUtils.equals( car.getColor(), someColor)) {
    if (car.getColor() eq someColor)) {

There is a massive difference in the amount of typing, and in clarity.

> Changing the language is a high barrier to entry

Language changes are necessary to have any kind of syntax for
specialization, that is not a rabidly horrible bunch of hacks. So I think
we are over that barrier already.

Millions will cheer & thanks you!

> and personally,  it seems like eq is just shorthand for a generic method
that can deal with this
> just as well.

Logically, 'equals' is an _operator_ not a _method_. Now is the time to get
this right. Alongside specialization, the Java 10 release will be marked
with fireworks, champagne & celebration.

> one language change I'd appreciate is the elvis operator since you can't
emulate that via lib.

Really, we can only consider the most concise & conservative set of
operators -- that will stand on their own, solve the very biggest bugbear,
and not be subject to "scope creep". Having a clear boundary for features
is very important.

I like the Elvis operator too -- and case-insensitive equals for strings --
but I'm putting forward a bounded proposal, prompted by the need for
'equals' in Collections. I want to start with that; it's also the most
common form in Java application development.


Regards,
Thomas


More information about the valhalla-dev mailing list