[tex-k] Bug-report for the TeXbook: Not all non-primitive control-sequences are defined, ultimately, in terms of the primitive ones.

[ud.usenetcorrespondence at web.de]

> Hi Don,
> I must admit that I don't understand what's unclear. As far as I
> understand Knuth's statement there are primitives which allow you to
> write your own macros (other control sequences). You can't write
> your own macros without primitives like \def, \edef, \csname, etc.
> 
> Regards,
> Reinhard


If Knuth's statement had been meant as it is now put, he would not
have elaborated on the \accent-primitive, but on those primitives
whose purpose is performing assignments.


> On Dec 9, 2022 at 10:00:42, Reinhard Kotucha <reinhard.kotucha at gmx.de>
> wrote:
>
> > On 2022-12-09 at 04:51:56 +0100, ud.usenetcorrespondence at web.de wrote:
> >
> > > Probably this has not yet been reported.
> > >
> > > TeXbook, Chapter 3: Controlling TeX says:
> > >
> > > | About 300 of TeXÕs control sequences are called primitive; these
> > > | are the low-level atomic operations that are not decomposable
> > > | into simpler functions. ***All other control sequences are
> > > | defined, ultimately, in terms of the primitive ones.*** For
> > > | example, \input is a primitive operation, but \Õ and \" are not;
> > > | the latter are defined in terms of an \accent primitive.
> > >
> > > I doubt that ***all other control sequences*** are defined,
> > > ultimately, in terms of the primitive ones.
> > >
> > > For example, with
> > >
> > > \def\mymacro{word}
> > >
> > > the control sequence \mymacro is not defined in terms of "the
> > > primitive ones" at all.
> >
> > \def is a primitive.

\def does not occur in the meaning of \mymacro.

If Knuth's statement had been meant as it is now put, he would not
have elaborated on the \accent-primitive, but on those primitives
whose purpose is performing assignments.

Ulrich