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Message-ID:  <20210420080026.GA823@polynum.com>
Date:         Tue, 20 Apr 2021 10:00:26 +0200
Reply-To:     Mailing list for the LaTeX3 project
              <LATEX-L@LISTSERV.UNI-HEIDELBERG.DE>
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From:         LARONDE Thierry <tlaronde@POLYNUM.COM>
Subject: LaTeX required primitives: some questions
To:           LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
Precedence: list
Envelope-To: <rainer.schoepf@gmx.net>
Status: R

Hello,

I have started to look at the implementation of the LaTeX required
primitives supplementary to TeX + e-TeX ones and I have some questions.

Note: I work with the definitions found in the pdfTeX manual and will
not look at the code since it is GPL'ed one and I don't want someone
later to claim that my code shall be released under GPL because my eyes
have touched GPL code.

PDF only primitives that I will not implement (correct?):

\pdfpageheight
\pdfpagewidth

Primitives that seem highly linked to PDF and that, to be implemented,
would need to draw in not ISO C routines but POSIX or MS specific
because they are linked to filesystems:

\pdfcreationdate
\pdffilemoddate

Primitives that seem highly linked to PDF but that can be implemented
using ISO C routines:

\pdffiledump
\pdfmdfivesum
\pdffilesize ? (size can be more than integer accepted by TeX)

Primitives whose output seem unclear:

\pdfnormaldeviate
\pdfuniformdeviate

said to generate "an integer" and, afterwards said to expand "to a list
of tokens". Do they provide, on each call, one integer with the defined
property or a series of a defined cardinal of such integers or an 
infinite series of such integers until interrupted?

General question:

What is the behavior expected on error (syntax error; out of range)?

Modifications:

The pdf prefix exists because the primitives were added to TeX in pdfTeX
but it is unfortunate because it seems to link the primitives to the
PDF format. I'd like to implement them without the pdf prefix and
provide simply a file for compatibility with \let statements. Would it 
be OK?

Primitives I plan to add (RFC):

\engine: a read-only ASCII token identifying the engine: ex.: e-TeX;

\apimajor: a positive or nul integer identifying a definite list of
	primitives provided;

\apiminor: a positive or nul integer identifying a definite behavior
	(nature, parameters, output, errors) of the primitives;

\apirevision: a positive or nul integer identifying an implementation
	of the (major, minor) combination---the major and minor identify a
	contract; the revision identifies a modification of the
	implementation of the contract including a correction because the
	implementation didn't actually provide the contract. I.e.: bug
	fixes, optimizations etc. without any contract modification. The
	contract is theoretical.

\outfmtlist: a series of ASCII tokens identifying the output format
	supported by the engine. Ex.: DVI1.0 (traditional DVI), PDF1.3 etc.
	The default format shall be listed first. (Note: I plan, some day,
	to extend DVI.)

\outfmtset: setting the output format, that shall be amongst the formats
	supported. If not, it returns an error and set the output format to
	the default one. Shall be set before \shipout and errors if used
	after output has started.

\outfmt: a token identifying the current output format.

Note: I will work progressively on this when I have a sufficient slot 
of time. So no timeline set.

Best,
-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
                       http://www.sbfa.fr/
Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C