APL Under-bar Characters

[Marcel Schneider]

On 17 Aug 2015 at 18:34, Doug Ewell  wrote [included subsequent exchange]:

> > I have heard that the problem was brought to Unicode consortium
> > before, and the answer was to just use the underline styling, as it is
> > apparently equivalent, but I do not think it is.
> 
> Combining character sequences are not "styling." Combining character
> sequences are plain text. They are not the same as marking a letter or
> word or paragraph in your word processor and clicking a button to make
> that text bold or italic or underlined.
> 
> In layman's terms, each combining sequence (base character plus any
> number of combining characters) should be treated as a unit, regardless
> of whether the sequence has been assigned a name. So these sequences are
> indeed equivalent to the APL-specific "underlined letter" characters
> used in non-Unicode systems.
> 
> > Underline styling usually connects the line from one letter to another
> > l̲i̲k̲e̲ ̲t̲h̲i̲s̲.̲ The under-bar characters do not do such connecting,
> > and are actually only for capital letters. so It would look more
> > L̲ I̲ K̲ E̲ ̲ T̲ H̲ I̲ S̲ (I added the spaces for dramatic effect).
> 
> TUS 7.0, Section 7.9 does say:
> 
> > The characters U+0332 COMBINING LOW LINE, U+0333 COMBINING DOUBLE LOW
> > LINE, U+0305 COMBINING OVERLINE, and U+033F COMBINING DOUBLE OVERLINE
> > are intended to connect on the left and right.
> 
> In that case, despite the text in Section 22.7 that Ken quoted, it seems
> that U+0331 COMBINING MACRON BELOW might be a better choice for APL
> "underlined letters" than U+0332 COMBINING LOW LINE. Compare A̱ḆC̱
> with A̲B̲C̲, noting that your font and rendering engine mileage may
> vary.

As Alex Weiner apparently used formatting in both examples, I didn't notice that the issue was to avoid having underlined capitals looking like if they were underlined with formatting. Indeed I see that APL must use the combining macron below (and good rendering engines).

Alex' concern is probably to be irked seeing all the mathematical alphabets in the SMP and no underlined for APL.

By contrast, following Khaled Hosny's soon reply, Alex' posted concern about character count resolves clearly as an unexpected software behavior, which is to be fixed at implementation level.

 

Marcel
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