[tex-k] potential errata in The TeXbook and TeX: The Program, Jubilee editions

Karl Berry karl at freefriends.org
Thu Nov 2 22:57:18 CET 2023

Hi Doug,

    which perhaps help elucidate DEK's original motivation for the separate

Thanks for mentioning that.

    logically, what is so untoward about opening group contexts
    one side of the tab mark, and closing them in a balanced way on the
    other? Wouldn't that be a feature, not a error?

Well ... since every cell in the table is implicitly in a group (as you
know), as both an author and macro writer, I can report that I am glad
that a group can't be opened in one cell and closed in another :). In
your scenario, I guess the implicit } to the left of the & would close
the last explicit {, and the implicit { to the right of the & would get
matched by the first explicit }. My mind is pretty boggled just writing
that description :).

I guess I could imagine some possible use for it (did you have something
specific in mind?), but the feature of catching misplaced groups at &
markers, i.e., getting errors sooner, seems more clearly useful to
me. It's already hard enough to debug alignments ... Just MHO.

Happy aligning,

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