# [tex-k] minor errors in TeXbook Appendix G concerning genfrac

Karl Berry karl at freefriends.org
Wed Dec 12 01:02:53 CET 2018

Hi Sophie,

1. TeXbook page A444 line 18 from the bottom mentions "let
$(\lambda, \rho)$ be the left and right delimiters". However it
never uses those names $\lambda$ and $\rho$ again, instead only
mentioning the "left delimiter" and "right delimiter" in step 15e on
page A445.

Well, they are trivially used at the end of item 15:
The values of $\lambda$ and $\rho$ are null unless
the fraction is with delims.''
But your point is taken nevertheless. I will consult.

2. TeXbook page A445 line 13 says to replace "the generalized
fraction by an Inner atom...". I believe this text is meant to
instruct replacing the genfrac by an *Ord* atom.
...
3. Relatedly, TeXbook page A445 line 14 (end of Rule 15e) does not
indicate how to proceed after this processing. In contrast, Rules 1
through 14 all end with an instruction ...

Ack, thanks. --karl.

P.S. Are you reimplementing math typesetting in some new system? Just
curious how you ended up here.