Implement an Elvis operator

[nikolay]

trafficstars

https://en.wikipedia.org/wiki/Elvis_operator

The above is more explicit than generalizing (or abusing, maybe?) the || operator. It's available in languages like Kotlin.

[anguslees]

Jsonnet is lazy. Why wouldn't regular || short circuit?

[sparkprime]

It does short circuit, but it does not either

1. implicitly cast things to bool
2. In the case that things are not bools, return the original thing instead of "true"

It differs from many scripting languages in this

[anguslees]

Ah, that last comment makes it clear to me that this relies on a notion of "truthy", which we don't have in jsonnet. Perhaps a null-coalescing operator (//) would be more clearly defined and useful in json-land (short circuit based on != null), and perhaps meet the original problem statement?

In related news, I note there is no problem statement in this issue :P

[nikolay]

@anguslees The null-coalescing operator // is nice as //= is possible in some languages and ?:= does not make sense.

[sparkprime]

Unfortunately // is a comment :)

[anguslees]

Unfortunately // is a comment :)

Oh duh :stuck_out_tongue_closed_eyes:

https://en.wikipedia.org/wiki/Null_coalescing_operator has a good survey of the operator in various existing languages. ?? might be a reasonable choice for jsonnet?

However, I say again: I feel like we're iterating a solution that doesn't actually have an associated problem - so we can't actually say if/when we've satisfactorily addressed any original issue.

[tavin]

I'm not a big fan of writing out thing() != null && thing() >= 123 etc. etc. Much nicer would be thing() ?: 0 >= 123 or even std.coalesce(thing(), 0) >= 123. Does that suffice as a problem statement?

[sbarzowski]

You can write your own coalesce function like that, no upstream support required. That said, it would be a valid addition to the stdlib as well.

And maybe coalesce should take an array to allow arbitrary number of values?