Re: multi-symbol variables

On 10/9/21 12:10 AM, Neil Soiffer wrote:
> I think I must not be getting your gist in:
> 
>     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*.
> 
> 
> The point of having defaults is precisely so that you know when adding intent is required 
> to convey some specific meaning that differs from the default. If software doesn't know 
> what a default is, then it should generate an intent value.

That's exactly what makes using defaults a bit tricky: To annotate a document
accurately, you'll need to know exactly which rules will be applied to know whether
or not they will need to be overruled.

> In case it isn't obvious, defaults should be simple, but not necessarily trivial. For 
> example, I think saying "msup" defaults to power is too trivial, but a simple rule like 
> "msup is a power except when the base is an <mi> and exponent is an <mo> , in which case 
> it is an identifier name." (feel free to pick holes in this -- it is just meant to be an 
> example showing that one can add a few special cases to a default to make it more useful. 
> This doesn't help for derivative, or transpose, or many other notations, but it does cover 
> x^*, the x^' examples in the math counts problems, along with it being a power.

Right. But I'm thinking that it would be perfectly reasonable for, say, a calculus
or dynamics context's rule set to say that
   <msup> <anything> <mo>prime</mo> </msup>
gets a default intent of derivative (in whatever syntax).
That would match *both* the f' and x' in the example.

>      Neil
> 
> 
> 
> On Fri, Oct 8, 2021 at 1:56 PM Miller, Bruce R. (Fed) <bruce.miller@nist.gov 
> <mailto:bruce.miller@nist.gov>> wrote:
> 
>     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/
> 


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

Received on Saturday, 9 October 2021 11:41:12 UTC