($.some_non_existent_key != 'anything') evaluates to false

[iiian]

input:

{}

expression:

$.some_non_existent_key != 'anything'

evaluates to

false

:(

[iiian]

I can fix it with

($.some_non_existent_key ? $.some_non_existent_key : null) != 'anything'

Is there a reason why it should be this way from a language design perspective? My initial intuition is that there might be some kind of ambiguity, but if that's true I'd love to know understand what the ambiguity is.

Thanks

[jhorbulyk]

The underlying concept is that undefined behaves like null in SQL and thus

• undefined = 'something' => false
• undefined != 'something' => false
• undefined = undefined => false
• undefined != undefined => false

Which is probably a concept that needs to be added to https://docs.jsonata.org/comparison-operators

[iiian]

Hey @jhorbulyk, thanks for the background, I appreciate it.

undefined != 'something' => false

If you don't mind my challenging a bit (respectfully, of course), what is the use case for this? I don't know a whole lot about SQL 3VL, but the idea that (undefined = 'something') and undefined != 'something' both evaluate to false seems like a logical inconsistency even for a 3VL system, and ultimately something that an end-user has to step around. Would it not be more SQL-esque to have undefined = 'something' evaluate to undefined?