On May 21, 2014, at 5:56 AM, Andreas Rossberg wrote:
> On 21 May 2014 14:33, Claude Pache <claude.pa...@gmail.com> wrote:
>>
>> I have thought about the right semantics (and the issues) of the existential
>> operator.
>>
>> user.getPlan?().value?.score;
>>
>> The intended semantics of `?` is that, whenever its LHS evaluates to `null`
>> or `undefined`,
>> the evaluation of the whole expression (or subexpression) is interrupted and
>> return immediately `undefined`.
>> In other word, it may be seen as an abrupt completion, as demonstrated by
>> the following expansion:
>>
>> (do {
>> let result = user // user
>> result = result.getPlan // _.getPlan
>> if (result == null) // _?
>> break // abrupt completion
>
> Drive-by comment: This would break the switch or loop statement
> surrounding the do-expression (or be an error if there isn't any). You
> need to wrap the statements into a labelled block and break that.
Well, completion records are just a specification device and if we need a new
[[type]] of abrupt completion to simplify specifying some semantics we
certainly could add it.
Allen
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