close #18092 document elif in case statements

[timotheecour]

close #18092

[alaviss]

Please also document that elif have to come after of. The manual is the language specification so we would want these details documented.

[timotheecour]

done

[Varriount]

While this technically documents "elif" in case statements (and is an improvement), I feel that there should be some additional explanation. Before this PR, I wasn't even aware that case supported elif, and I'm still not sure what it does, and when it should be used.

From the example, appears that elif allows the introduction of an arbitrary condition in a case statement? The example implies that it's only allowed at the end of a case statement, but is that true?

[timotheecour]

i feel it's clear enough and un-ambiguous as written, but feel free to suggest an alternative wording as code review comment.

I'm still not sure what it does, and when it should be used.

exactly what you wrote: From the example, appears that elif allows the introduction of an arbitrary condition in a case statement?

The example implies that it's only allowed at the end of a case statement, but is that true?

within a case statement, yes

[alaviss]

The code example is not the spec, it's... an example.

We already have a decent amount of writing right below it, and I think we should expand the paragraph talking about else to talk about elif as well.

[timotheecour]

The code example is not the spec, it's... an example.

yes and no; in this case I agree (and have updated spec description), but in other cases (in particular description of edge cases in APIs) it may makes sense to treat examples as spec because the alternative would be both non-DRY and add no value for readers compared to a well written (and compiler checked) runnableExamples.

I also mentioned the special case of string and mentioned the spec might change (refs #11474 (comment))

[Varriount]

The behavior an example describes tends to be implicit - my previous comment on elif's behavior was a guess. If not repeating information is a priority here, it would be preferable to go with an explicit description of elif's behavior over an implicit example.

[Araq]

The spec should say something like: "elif" in "case" is handled just like "else: if".

[timotheecour]

PTAL