About boundary characters

Didier Verna didier at didierverna.net
Thu Sep 19 14:21:07 CEST 2019

I wrote:

>   I found 24602 fonts in TeX Live 2019 with a non-zero width RBC. Here
>   are a couple of examples.

  Finally, I found 199 fonts with lig/kern instructions for a "left
boundary character", whatever than means (special last instruction in
the lig/kern array). Looking at the output of tftopl for a couple of
those, it appears that this program lists those instructions under the
(unique) BOUNDARYCHAR label, which happens to also be the right boundary
character. I've tested all the TeX Live fonts, and apparently, there are
no fonts for which a lig/kern program for a left boundary character
would be defined (special /last/ instruction in the lig/kern array)
without also having a definition for a right boundary character (special
/first/ instruction in the lig/kern array).

  Conclusion: I'm almost convinced now that the boundary character is
indeed unique, and that the terminology in TeX: the Program [545],
making a difference between left and right, is misleading.

Resistance is futile. You will be jazzimilated.

Lisp, Jazz, Aïkido: http://www.didierverna.info

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