“Who said anything about {x}?” is an idiomatic equivalent to “Why did you bring up {x} unprompted?” I think you're trying to say that unlabeled formulas are no

“Who said anything about {x}?” is an idiomatic equivalent to “Why did you bring up {x} unprompted?” I think you're trying to say that unlabeled formulas are no better or worse than unlabeled graphs and the like, but calling a formula a “string” is muddling it up. (If that is what you meant.) Because we're talking about floating-point data types, people are likely to think of the string data type.