Is there actually a notation and + operator for which 1 + 1 = 2 is ambiguous? Only being semi-rhetorical, I'd be interested to know if there is one. (Modular arithmetic is not considered ambiguous, at least not in the math neck of the woods.)
Not really answering your question, but more to the point of the discussion in my opinion, a() + b() could be ambiguous if a() and b() are functions with side effects and the evaluation order of the +-operator is not specified.
