Re: DEC Technical Character Set summation symbol corners

On 2025-12-25 09:40, [email protected] via Unicode wrote:

> In L2/98-354 (https://www.unicode.org/L2/L1998/98354.pdf), the 
> following characters were proposed for DEC Technical Character Set 
> compatibility:
>
> * E0AE  Right ceiling corner                   DEC Tech 03/05
> * E0AF  Right floor corner                     DEC Tech 03/06
>
> However, in L2/00-159 
> (https://www.unicode.org/L2/L2000/00159-ucsterminal.txt) which was 
> incorporated into Unicode 3.2, those characters were withdrawn:
>
>    E0AE  Right ceiling corner                       U+2309 (1)
>    E0AF  Right floor corner                         U+230B (1)
>
> (1) These characters were in Unicode all along, but the shape shown in the
>      Unicode book was different from the shape on the terminal.  However,
>      this is not sufficient reason to have two versions of the same symbol.
>
> However, in DEC Technical Character Set (vt100.net) 
> <https://urldefense.com/v3/__https://vt100.net/charsets/technical.html__;!!BDUfV1Et5lrpZQ!Sz6zze1z-M_LTSPW0rIIzWUQNelFKnVEyxjuZ9heR5jLaL5gUpYG6I0qDcmkLRMrcElIb4gqD0QQLkFGildA6qyV$> the 
> usage of those characters is explained as being parts of the summation 
> symbol, and the left side of those characters connect to U+2500.
>
> As far as I know, the floor and ceiling symbols usually have similar 
> height to brackets (with the horizontal stroke being on bottom or top 
> of the bracket height), and are used in pairs of left and right 
> glyphs, which is completely different from the DEC Tech 03/05 and DEC 
> Tech 03/06 characters. Is there any typographical precedent of floor 
> and ceiling symbols being used with a centered horizontal stroke or 
> with a horizontal connection to other characters?

The idea of "typographical precedent of floor and ceiling symbols being 
used with a centered horizontal stroke" seems to me a non-sequitur from 
the content at DEC Technical Character Set (vt100.net) 
<https://urldefense.com/v3/__https://vt100.net/charsets/technical.html__;!!BDUfV1Et5lrpZQ!Sz6zze1z-M_LTSPW0rIIzWUQNelFKnVEyxjuZ9heR5jLaL5gUpYG6I0qDcmkLRMrcElIb4gqD0QQLkFGildA6qyV$>. 
The latter alludes to a 2-d layout system by which parts of a sigma sign 
is assembled from eight graphical components to make a 2x3 or 3x5 
composite graphic. The former talks about formatting of linear plain 
text with general-purpose fonts.

I can see the benefit of providing a mapping between the code units in 
the DEC TCS and Unicode. I don't think that implies that ordinary plain 
text and text formatting mechanisms should be able to perform the 2-d 
layout described by DEC TCS. If I were implementing DEC TCS in a modern 
OS and app, I would either use graphics mechanism to draw the sigma, or 
an app-specific font where the glyphs have the size and relationships 
which the app requires.

Does this answer your question? Or, reject the premise helpfully?  Best 
regards,
      —Jim DeLaHunt