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Date:         Thu, 16 Sep 2010 10:42:07 +0100
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From: Chris Rowley <c.a.rowley@OPEN.AC.UK>
Subject: Re: e-TeX low-level expertise needed Re: Allocation of registers
To: LATEX-L@listserv.uni-heidelberg.de
In-Reply-To:  <19601.55875.121644.485219@morse.mittelbach-online.de>
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Status: R

No intention to be 'hard on Peter'.  Merely a suggestion that, at least in the documentation, something could be done to clarify this.  Whether this is in The Manual or not depends for whom that manual is intended.  TeX itself is always quite good at telling us, somewhere, when tokens are effectively ignored.

More generally, why is there suddenly some 'subjective moral standard' about
what a software system should or need not do?

A vaguer question: Is the level of the relatively efficiency of the types of register of any practical consequence in the 21st century?

chris

-----Frank Mittelbach <frank.mittelbach@LATEX-PROJECT.ORG> wrote: -----

To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
From: Frank Mittelbach <frank.mittelbach@LATEX-PROJECT.ORG>
Date: 16/09/2010 09:50
Subject: Re: e-TeX low-level expertise needed Re: Allocation of registers

Chris,

 > >>
 > I did a few tests. As the e-TeX manual says, you can't \insert beyond 
 > 254. \insert255 gives the special 'You can't \insert255' error (as 
 > without e-TeX), and anything higher is a bad register code. (The 
 > {<stuff>} seems to vanish.)
 > >>
 > 
 > Ah, but is that vanish b: or vanich c: :-) ??   
 > I think we should be told!  I suspect b: (ie the tokens in <stuff> are
 > never processed at all) but what a waste of tokens...!!  And the error
 > message or something should point this out to B.L.Euser 

you shouldn't be too hard on Peter (who I guess wrote that code) --
if eTeX replies with a "bad register code" error then I think that is good
enough even if perhaps not the best error message you can get. And frankly
what happens after a severe error is kind arbitrary so that it really doesn't
matter much in my opinion whether you will be told in the manual exactly how
the program recovers.

So in my opinion, if eTeX manual states that \insert only works on 0-254 and
then also goes and generates an error if you try differently then it does all
that is needed.

A consequence for us seems to me that indeed we can't do much more than
reserve a range for use with inserts at least while we live in coexistance
with code that uses inserts.  The boundary is reserving all lower registers,
but that is most certainly overkill and as the higher registers are supposed
to be less efficient we should probably not waste too much of the main
registers.

For now I think providing an additional 30 inserts is the right level

frank
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