Negative/Negation Sign

[Asmus Freytag]

On 10/29/2022 7:18 PM, Gabriel Tellez via Unicode wrote:
>
>     interestingly enough, one of the sources cited for the Wikipedia
>     article actually has a mapping to U+203E (spacing overline). 
>
> You mean... it's contested?!?!

Meaning whatever you like. In the source document the comments give what 
is effectively a numeric character entity that supposedly can be used to 
achieve the same appearance. However, the appearance of the glyph in the 
bitmap font clearly does not match that of U+203E (the latter is both 
longer and placed higher in the character cell).

So, I would call it a mistake.

If it had been the case of some other code point that also looks similar 
to what is actually displayed on the calculator, I would be more 
comfortable with considering it the result of a reasonable difference in 
opinion of how to best map the character.

>     These characters were in Unicode from very early on. Unlike some
>     of the later additions there is no link to a particular citation
>     "in the wild". Instead, the original repertoire collected a
>     superset of then existing character sets in reasonably wide usage.
>     If any of their members violated Unicode encoding principles, they
>     were added as compatibility characters (to facilitate round trip),
>     otherwise as ordinary characters.
>
>
> Compatibility characters from what set?
>
>     APL contents itself with U+207B SUPERSCRIPT MINUS
>
>
> No? Other then on one Wikipedia Page, most places I looked (including 
> the APL wiki) used ¯ U+00AF MACRON.

Because that was available before Unicode. There's nothing wrong with 
it, if that's a notation you like, but it doesn't match the look of the 
symbol in the TI bitmap fonts.

So, for example, U+203E and U+00AF are much closer in appearance than 
either is with U+207B. It might be that the suggested character entity 
was chosen to make the notation look more like APL.

That's not unreasonable, per se. However, for a plain-text mappings 
(unlike display effect of using a character entity in a suitable 
environment) it would have been better to either stick with something 
that matches the original appearance or something that matches some 
other plain text format that uses a comparable notation.

It all depends. Are you simply interested in round tripping data through 
Unicode? Are you interested in passing text of to some existing 
mathematical interpreter? Or are you interested in creating a text 
stream that somewhat looks like what the calculator is showing, perhaps 
for discussing results or programming techniques?

All three may conceivably have different mappings, but none of these 
cinches the case for adding something new to Unicode at this point.

A./


>
> On Sat, Oct 29, 2022 at 8:18 PM Mark E. Shoulson via Unicode 
> <unicode at corp.unicode.org> wrote:
>
>     The APL language used a high-minus for negative numbers and a normal
>     hyphen-minus for the operator, monadic or dyadic.  The high-minus was
>     syntactically part of the number, while the regular minus operated
>     on a
>     number (which would affect its precedence.) Come to think of it, when
>     they were teaching us negative numbers in grade school I think my
>     math
>     book initially used a high-minus sign and then introduced the concept
>     that negation was an operation that can be done to numbers and
>     from then
>     on used the regular minus sign.
>
>     Non-typographically, Lojban mathematical syntax (mekso) distinguishes
>     {vu'u}, the subtraction operator, from {ni'u}, the negative-number
>     indicator.  The latter is syntactically considered a *digit*,
>     while the
>     former is an operator.
>
>     Unicode has a long history of tolerating the typographic weirdness of
>     APL (all those APL symbols).  That there isn't an APL high-minus sign
>     already would indicate to me that APL contents itself with U+207B
>     SUPERSCRIPT MINUS and that's Just Fine.
>
>     ~mark
>
>     On 10/28/22 18:10, Doug Ewell via Unicode wrote:
>     > Gabriel Tellez wrote:
>     >
>     >> Is superscript minus use for this?
>     > Is *anything* used for this, outside of the TI-83 and TI-84
>     machines, other than an ordinary minus sign or hyphen-minus?
>     >
>     > There are actual mathematics experts on this list, but my
>     understanding is that normal mathematical notation—as used both by
>     experts and the general public—uses the same symbol for both unary
>     and binary minus. The TI calculators may have distinguished
>     between the two to make input or internal parsing easier.
>     >
>     > --
>     > Doug Ewell, CC, ALB | Lakewood, CO, US | ewellic.org
>     <http://ewellic.org>
>     >
>
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