Precedence of otherwise operator

[michaelhkay]

I made a mistake when specifying subsequence-where, caused by misunderstanding the precedence of the otherwise operator: see issue #1001.

In the expression

let $start := index-where($input, $from)[1] 
              otherwise count($input) + 1

I failed to realise that otherwise binds more tightly than +.

I'm opening the issue to solicit views as to whether we have got this right.

One might take the view that the closest thing to otherwise in other familiar language is the ternary conditional operator, which has lower precedence than anything else including and and or; but then, its first operand is a boolean expression while it's relatively unlikely that the operands of otherwise will be boolean. I'm therefore thinking that it might be best to put it between 'eq' and '||`, so

$a eq $b otherwise $c || $d

parses as

$a eq ($b otherwise ($c || $d))

[ChristianGruen]

Yes, that looks like a good choice. I’ve come across a similar problem with the current precedence rules in a project a short while ago.