[texhax] Some puzzling TeX (\@sptoken)

[Uwe Lueck]

"Philip TAYLOR (Webmaster, Ret'd)" <P.Taylor at Rhul.Ac.Uk> wrote 01.06.2011 21:48:38:
> Uwe Lueck wrote:
>> The essential "thesis" of my earlier posting (below) was:
>>
>> an explicit definition of<optional spaces> does not provide
>> an explicit definition of<one optional space>
>
> <one optional space>\is<space token>\alt<empty>
>
> The quantity ^\<space token>, which was used in the syntax of \<optional
> spaces> above, stands for an explicit or implicit space.

Yes, as the rule for <one optional space> cannot be derived
from another rule like <optional spaces>, the TeXbook is so
astonishingly careful to state it separately, cf.

    http://tug.org/pipermail/texhax/2011-June/017598.html

that I was summarizing.

That line declaring <one optional space> appears 1.5 pages
after <optional spaces>, after 10 rules concerning numbers,
7 pages before <let assignment>. Appelt!

Cheers,

    Uwe.