Dmitry Soshnikov wrote:
Will the "Existential Operator" for properly accessors be something
interesting to consider for ES7 spec? Currently CoffeeScript uses it well.
Please see
http://esdiscuss.org/topic/sept-18-tc39-meeting-notes#content-2
and find "ARB: This is non-compositional". Citing text for reader
convenience:
Existential Operator (strawman discussion)
(Presented by Brendan Eich, Mozilla)
Significant desire include a null and undefined check in syntax/operator
form (a la coffeescipt)
| o = {}
r = o?.p.q.r
r = o?.p?.q.r
|
Mixed discussion about the needs and use cases as they apply to
coffeescript code.
ARB: This is non-compositional
| o = {}
r = o?.p.q.r
r = (o?.p).q.r
r = o?.p.q.r()
|
Results in…
| var o, r;
o = {};
r = o != null ? o.p.q.r : void 0;
r = (o != null ? o.p : void 0).q.r;
r = o != null ? o.p.q.r() : void 0;
|
Non-starter.
DH: Why not an operator that needs to be explicit?
| o?.p?.q?.r
|
LH: Why would you ever even use it on the first?
BE: Forget all of the problems with coffeescript's impl, the need exists.
YK: In the common cases, where it works, it works well. Where it
doesn't, it falls apart unexpectedly.
WH: What about other contexts such as p?[x], p?.q[x], and p?(x) ? [Note
that grammar problems arise for some of those.]
General agreement.
*Conclusion/Resolution* Seems useful, but not now. Semantics are unclear
---
The notes ended a bit too optimistically in my view! "Non-starter".
/be
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