[tex-k] incorrect explanation of <argument>s in Chapter 25 of The METAFONTbook

[胡亚捷 (Hu Yajie)]

Here's a minor glitch in The METAFONTbook, which I assume you can defer
until the next tuneup.

Page C210, line -13 implies that the <argument>s in the syntaxes of
Chapter 25 stand for "expr" arguments, but they actually stand for
arguments of any kind. In my earlier report
https://tug.org/pipermail/tex-k/2020-July/003263.html
I pointed out that future pen arguments are permitted if you say
"def foo secondary p" instead of "def foo expr p", and Knuth added a
<future pen argument> in the 2021 tuneup, so he clearly had arguments
of any kind (primary/secondary/tertiary/expr/to a for loop/etc.) in his mind.

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My earlier reports:
https://github.com/dine2014/texbook-mfbook-bugs/