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<div>I am quite certain that the use of \def, \edef, \xdef or \let was not meant, but rather that the expansion of the macros was meant. The passage is a restatement of how macro languages in general work: tokens are expanded until they can't be expanded anymore and the remaining primitives or "terminal symbols" are then passed to the compiler.</div>
<div>Ulrich is correct, primitives are not only control sequences, they are also plain characters, the beginning-of-group and end-of-group tokens, the enter-math-mode and exit-math-mode characters, etc. It's another way of putting what he otherwise describes as TeX's "mouth" and "stomach" (perhaps not his most appetizing image) --- what other people call scanning and parsing.</div>
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<div style="margin: 0 0 10.0px 0;"><b>Gesendet:</b> Samstag, 10. Dezember 2022 um 18:29 Uhr<br/>
<b>Von:</b> "Yannis Haralambous" <yannis1962@gmail.com><br/>
<b>An:</b> ud.usenetcorrespondence@web.de<br/>
<b>Cc:</b> tex-k@tug.org<br/>
<b>Betreff:</b> Re: [tex-k] Bug-report for the TeXbook: Not all non-primitive control-sequences are defined, ultimately, in terms of the primitive ones.</div>
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<div>I think the debate is about the semantics of the verb "to define" and of the expression "in terms" in Don's text.
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<div>If by "defined" he meant "defined through the \def or the \let command" and if by "in terms" he meant that</div>
<div>"strictly only that" then Ukirch might have bern right.</div>
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<div>But IMHO this is not what Don meant.</div>
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<div>What he meant is that in the expansion of commands you can use many things including primitive and non-primitive</div>
<div>commands, but if you continue expanding you will end up with having no non-primitive commands.</div>
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<div>If he meant otherwise he would use neither "in terms" nor "ultimately". This statement is not part of a formal grammar,</div>
<div>it is just a comment about the special status of primitive commands.</div>
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<div>Le 10 déc. 2022 à 16:18, ud.usenetcorrespondence@web.de a écrit :</div>
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<blockquote>***All other control sequences are<br/>
| defined, ultimately, in terms of the primitive ones.***</blockquote>
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<div>Yannis</div>
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