Re: multi-symbol variables

On 08/10/2021 04:09, David Farmer wrote:
> Taking this discussion out of GitHub.  I hope this is the right
> place.
> The important point which has arisen, which I believe we had not
> discussed previously, is how to mark a multi-letter string as
> representing a single variable.  For example, on this page:
> it says
> Interest = p \times r \times t .
> Here "Interest" is an 8 character string which represents one
> quantity.
> This is analogous to the situation in our recent discussions,
> where B' is just one quantity which happens to be a string of
> two characters.  The fact that one of the characters is a prime
> is not the main issue.  I mentioned an example where a_1 was a
> (subscripted) string which also is really just a single variable.
> Prior to this week I don't think we had discussed the fact that
> B' is a 2-character quantity, while f' -- assuming that means the
> derivative of f -- is the object f on which ' is acting.
> The only point I am trying to make here is that we need a way to
> indicate that a collection of characters is really in indivisible
> unit which represents a single quantity.  The recent discussions were
> made more difficult by the fact that this had not been discussed
> previously.
> I suggest that " B' " should be handled the same way as " Interest "
> would be handled in the formula above.
> Regards,
> David Farmer
logically I agree that "B'" is the same as "Interest" but typographic 
details don't always follow logic,.

Interest is <mi>Interest</mi> which does the right thing automatically 
due to the rule about multi-letter mi using upright font. So it is easy 
in that case to say the default intent is the single name "Interest"

B'  is <msup><mi>B</mi><mo>&prime;</mo></msup> or arguably 
<msup><mi>B</mi><mo>'</mo></msup> or <mi>B'</mi>

Only the last of these has a natural intent as a single identifier (and 
traditionally mathml has been explicit that that form is not correct)

mathml's traditional solution to this was to allow presentation in 
content mathml token elements so


is unambiguously a variable name B' but we are trying to do without 
content mathml here so..  I think the natural intent to use here would be

<msup intent="B prime"><mi>B</mi><mo>'</mo></msup> if the default intent 
on <mi>Interest</mi> is intent="Interest"


<msup intent="variable-name"><mi>B</mi><mo>'</mo></msup> if the default 
intent on <mi>Interest</mi> is intent="variable-name" (or some other 
known keyword to be decided) that means it's a variable and has natural 
reading just by reading the content.



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Received on Friday, 8 October 2021 07:42:56 UTC