# Re: multi-symbol variables

• From: Miller, Bruce R. (Fed) <bruce.miller@nist.gov>
• Date: Fri, 8 Oct 2021 16:55:03 -0400
• Message-ID: <e6a354d2-460a-1b1a-09eb-07c7614e5173@nist.gov>
```On 10/8/21 3:00 PM, Neil Soiffer wrote:
> To return to some of the examples. If someone uses a prime, double prime, etc, a literal
> reading "x double prime" doesn't need anything special

Deyan addressed the question of what a "natural" reading of primes may or may not be.

I want to emphasize a different point about specialized pronunciation & "defaults".

In real life, I've encountered things like "f' = x' + ....",
where for example f is a function and prime means to take its derivative,
while x' is a unique variable, presumably some transformation of x.

If we *never* are going to concern ourselves with output other than the literal:
"eff prime equals ecks prime dot dot dot"
and leave it to the hearer to figure it out, then there's no issue.
(but that seems not to be your POV)

If, on the other hand, we are expecting to say something different for
a derivative (whatever it might be), then the two instances will *have*
to be distinguished.
If there were no defaulting, we would simply assert that f' is a derivative.
(but that seems not to be the POV of several folks)

But if there are contexts & defaults applied, you have to make sure
that x' is *not* treated as a derivative (by whatever means).

The point is that we not only have to provide a way to assert what
something *is* (or how it should be pronounced), but in the presence
of defaulting, we essentially have to say what it's *not*.

bruce
--
bruce.miller@nist.gov
http://math.nist.gov/~BMiller/
```

Received on Friday, 8 October 2021 20:55:22 UTC