Hello,
There is a discussion on Slack (and in the Patterning spec) about how Observation Operators and Qualifiers interact. I'm bringing it here to have a full SC discussion.
Link to Patterning Spec:
The question is, do Qualifiers (REPEAT or WITHIN or START/STOP) apply to the immediately preceding Observation _expression_, or to all preceding Observation Expressions?
The spec has it as not greedy, option 2 below.
1) Qualifiers are greedy and apply to all preceding expressions (have low precedence than ALONGWITH/FOLLOWEDBY) : `[ a ] ALONGWITH [ b ] REPEAT 5 TIMES` results in 5 a's and 5 b's (to get other result, you need to use: `[ a ] ALONGWITH ([ b ] REPEAT 5 TIMES)`)
2) Qualifiers are not greedy and only apply to the immediately preceding _expression_ (have a higher precedence than ALONGWITH/FOLLOWEDBY): `[ a ] ALONGWITH [ b] REPEAT 5 TIMES` results in 1 a and 5 b's. (to get other result, you need to use: `([ a ] ALONGWITH [ b ]) REPEAT 5 TIMES)`).
There is also the point that some qualifiers make sense to be greedy, REPEAT and START/STOP, while WITHIN be non-greedy as it doesn't make sense to apply to only one Observation _expression_. I would prefer NOT to split these as it will confuse writers and readers of these patterns. Yes, they could be described w/ a simple precedence table, but that would just add another rule that people have to memorize.
I do not have a strong preference for one or the other. I personally think that 2 makes slightly more sense, as if you write a long pattern w/ multiple qualifiers, you'll end up using less parens than the other way.
Thanks for your input.
John-Mark