[tex-k] glaring error in Chapter 23 of The TeXbook

[胡亚捷 (Hu Yajie)]

The TeXbook, page 252, line 6 says that you can customize TeX's output routine
by ``redefining the control sequences \headline and \footline''. But \headline
and \footline are token list registers, not macros. You are supposed to change
their content, not to redefine them with \def (which messes plain TeX's output
routine), \toksdef or \newtoks (which wastes allocation space).

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Previous reports:
https://github.com/dine2014/texbook-mfbook-bugs/blob/master/bugs.md