Support nullish coalescing operator ?? in mathjs expression language

[gwhitney]

Describe the suggested feature
Currently x ?? 0 is a syntax error. It would be handy if this meant the nullish coalescing operator denoted by ?? in JavaScript. For example, one could then do object lookup with a fallback : {foo: 7, bar: 3}["baz"] ?? 0.

Current workaround
nullish(x, y) = (x == null or x == undefined) ? y : x; nullish(null, 0)

I am not aware of a short way to test for null or undefined unlike x == null in JavaScript which is true if x is either null or undefined; in mathjs expression language it is true when x is null and false when x is undefined.

[josdejong]

Having the nullish coalescing operator would be great!

[ikemHood]

Hey @josdejong

I would like to give this a shot

[gwhitney]

As the suggested syntax enhancement has been approved by the head of MathJS, a PR is welcome. Of course be sure that the change does not disrupt the ternary operator x ? 1 : 0 and add tests for variants like x ?? 0, x??0, etc.

[josdejong]

Thanks @ikemHood , please let us know if you need any pointers.

[Anuragyadav622003]

I'd love to work on this as I have experience with parsers and expression evaluators. I'll add ?? support by updating the tokenizer, parser, and evaluator with proper precedence and tests.

[gwhitney]

I believe @ikemHood is working on it; you should check with that person to avoid duplicating effort.

[ikemHood]

Yes. @gwhitney. made a PR (#3497)

waiting for a review