[tex-k] Index Entry of \not in The TeXbook

Sebastian Miele sebastian.miele at gmail.com
Sun Nov 17 04:04:43 CET 2019

In the index chapter, knuth-dist/tex/texbook.tex contains the following

|\not| ( $\not$ ), @133, +358, @436--437.

In plain.tex, \not is \mathchardef'ed to a zero witdh character that
protrudes to the right. In e.g. just ( $\not$ )\bye processed by pdftex,
the character protrudes through the closing right parentheses.

In my (quite old) print version of The TeXbook, it protrudes, too.
manmac.tex contains no occurrence of \not. So it is quite probable that
it is not redefined there. I did not find a redefinition in texbook.tex,
too, although the search for it was rather superficial.

After some hesitation I took the liberty and ran texbook.tex through
pdftex. In the result the character protrudes through the closing
parentheses, too.

This may be considered an "aesthetics bug".

Best wishes

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