Willing to bet it's either "sonst" or "andernfalls"... I'd suspect the latter, the former is a little bit too informal for mathematicians. Both of these are commonly used for case enumerations in math.

As a research mathematician, I happily use "sonst" in e.g. case distinctions (well, in my undergrad lecture notes; papers are written in English ) and wouldn't use "andernfalls" as it is simply too long :-). Moreover, if they had looked up "andernfalls" in a dictionary, they would have found "otherwise" as translation. For "sonst", the number 1 translation in all dictionaries I have around or found online, is "else".

So I firmly believe they used "sonst".

Maybe. On the other hand, "andernfalls" is a bit long as a keyword.

Except that you’d then have to make all the operators postfix to match how German puts the verbs at the end of subordinate clauses :-p

“wenn a b ==...”

ah but it's more complicated because only the main verb is at the end of the sentence, so if you need an auxiliary or you have a copular construction like "ist gleich", you need to split the verb phrase...

in fact, Germans would say (and do say, e.g. in mathematics) "wenn a gleich b" as a shorthand for "wenn a gleich b ist".

Interesting. Seems sorta like the English shorthand "if a less-than b, do this" (as opposed to "if a IS less than b, do this"). "Equal" is almost a different story since it works as a verb as well as an adjective.

Yes, in English has the verb "to equal", which German doesn't. The verb "gleichen" doesn't work, because it means "to be similar to".

Thanks for the insider German knowledge!