User blog comment:Hyp cos/R function II/@comment-5529393-20150405161701

A few questions:

You refer to "braces not a separator". What exactly constitutes a separator?

Are you allowed to have {} or {+m} with nothing inside?

If not, how is B3 ever invoked? Before an innermost right brace there will always be some number, so we will scan that before we ever get to case B3. If we did invoke B3, then scanning the first ⊙ will be no use, since we already scanned past that and didn't find anything.