path: root/info/digests/tex-implementors/message.42

Date:	  11 Sep 93				Message No:	042

To:	  TeX implementors and distributors

From:	  Barbara Beeton

Subject:  TeX 3.1415 and other updates -- file 2 of 2


########################################################################

Commentary from Don Knuth

>>> DEK message accompanying shipment
					[ received 6 Jun 93 ]

Barbara, I don't know when (if ever) you plan to put out another
supplement to TUGboat containing TeX errata.  But I did make some
changes to errata.tex that you should know about:

    New file errata.eight contains the changes subsequent to
    errata.seven that are in the "final" publication form of
    Volumes A-E (and the TeXbook and MFbook paperback variants).

    Henceforth errata.tex contains the changes subsequent to the
    final versions.  The final versions will not be updated in
    future printings.  But I will keep my electronic copies up
    to date in preparation for future electronic publication.

Plain format 3.1415 includes two inportant changes regarding the \b
accent in slanted fonts and the \upbracefill \downbracefill macros.

Please encourage everybody to install this version ASAP.  It is
documented in errata.tex; five pages of the TeXbook are slightly
affected, but (as I say) the hardcopy versions will no longer be
updated.

Similarly everybody needs plain.mf version 2.71 (it has two important
corrections to the cutdraw macro).

						don

encl:	errata.tex
	errata.eight

************************************************************************

>>> TeXbook / MFbook bugs

Date: 26 Jan 1993 18:19:09 +0100
From: Roegel Denis <Denis.Roegel@loria.fr>
Cc: roegel@pandore.loria.fr
Subject: bug in TeXbook

Mrs Beaton,

I noticed a few weeks ago that you have the privilege to
report bugs to the Grand Wizard. Here is a small one that
appears in my printed edition of volume A (tenth printing)
as well as in the files dated may 1991:

page 320, answer to exercise 17.12: there is either a parenthesis
too much or one lacking.
[ dek:								$2.56
]

Denis (roegel@loria.fr)
-------

[ the following are in consequence of repagination; a paragraph that
  was formerly broken between pp.271-272 is now complete on p.271.
  it is certain that other index items are involved as well.
]
[ dek:						<chardef token>
]
Date: 19 Feb 1993 12:21:42 +0100
From: Roegel Denis <Denis.Roegel@loria.fr>
Subject: TeXbook bugs (cont'ed) ?

Mrs Beeton,

Yesterday, when I was reading in the TeXbook the entries related to
\mathchardef, I found that there are two slightly wrong entries in 
the index, viz.,

  On page 471, \mathchardef points to page 272, but I think 271 was meant.

  The same problem happens for \chardef: 272 instead of 271.
[ dek:								$2.56
]
Well, that's all!

Denis (roegel@loria.fr)
-------

Date: Thu, 09 Apr 92 00:16:21 BST
From: Chris Thompson <CET1@UK.AC.CAMBRIDGE.PHOENIX>
To: Barbara Beeton <BNB@COM.AMS.MATH>
Cc: Robert Hunt <REH10@UK.AC.CAMBRIDGE.PHOENIX>
Subject: TeXbook (chapter 26) error from Robert Hunt

Barbara,

Here is a TeXbook bug report from Robert Hunt:

> (a) TeXbook error: chapter 26 ("Summary of Math Mode") claims that
> \unhbox is an invalid command (and so generates an error) in maths
> mode. In fact, it is allowed so long as the box being unboxed is void!
> (The \S and \P macros make use of this fact.)

This is right, I think. \unhbox and \unhcopy are not mentioned in
Chapter 26, explicitly or implicitly, in the current texbook.tex,
and so would fall into the "none of the above" on page 293. But they
are in fact allowed in math mode provided the box register is void
[ dek:								$2.56
]
(tex.web section 1110, |unpackage|: this case is actually mentioned as
change 232 in tex82.bug, TeX version 0.999). The fact that \leavevmode
is allowed in math mode (doing nothing) depends on this. (It is called
from \S and \P, hence Robert's mention of them above.)

Chris Thompson
-------

Date: 3 Feb 1993 09:58:52 GMT
From: schwab@lamothe.informatik.uni-dortmund.de (Andreas Schwab)
To: tex-news@SHSU.EDU
Subject: Typesetting bugs in The TeXbook and The METAFONTbook

There are some typesetting bugs in The TeXbook (March 1992) and The
METAFONTbook (February 1992):

1. In the last line of page 358 in The TeXbook there is too much space
between `that' and `give'.
[ dek:		(and it talks about "the proper spacing"!)	$2.56
]
2. In the middle of page 296 in The METAFONTbook there is one comma
too much after `tension 4..'.
[ dek:								$2.56
]
3. Likewise in The METAFONTbook, on page 299, second text line, the
name `Bernshte\u\in' is misspelled.  I don't know the correct
spelling, but `Bernshtein' occurs three times and `Bernstein' only two
times. On the other hand, one of the occurences of the latter form is
in the index...
[ dek:	His name usually transliterated with just ...stein but when
	I'm transliterating an original Russian mane I aim to be
	consistently sh for {\cyr sh}.  The recent printings have
	this corrected.
]

--- texbook.tex~	Wed Mar 25 20:40:20 1992
+++ texbook.tex	Fri Jan  1 20:07:40 1993
@@ -20089,5 +20089,5 @@
 After defining characters ^|\ldotp| and ^|\cdotp| that act as math
 punctuation, it is easy to define ^|\ldots| and ^|\cdots| macros that
-\vadjust{\penalty-50} % fairly good breakpoint (on July 27, 1983)
+\vadjust{\penalty-50}% fairly good breakpoint (on July 27, 1983)
 give the proper spacing in most circumstances. Vertical and diagonal
 dots (^|\vdots| and ^|\ddots|) are also provided here:
--- mfbook.tex~	Wed Mar 25 20:17:08 1992
+++ mfbook.tex	Fri Jan  1 18:00:58 1993
@@ -15944,5 +15944,5 @@
 With slight changes to this code, you can get weird effects.
 For example, if the definition of |rp| is changed to `|]..tension 4..|',
-^^{tension}, and if `|scaled|~|5pt|' is inserted before `|withweight|',
+^^{tension} and if `|scaled|~|5pt|' is inserted before `|withweight|',
 the image will be an ``^{almost digitized}'' character:
 \displayfig Daa (18.5mm)
@@ -16099,5 +16099,5 @@
  (1-t)^{n-k}t^{k-1}u_k,$
 \enddisplay
-a Bernste{\u\i}n polynomial of order $n-1$.)
+a Bernshte{\u\i}n polynomial of order $n-1$.)

 Our problem is to change the meaning of \MF's ^{brackets} so that
--
Andreas Schwab
schwab@ls5.informatik.uni-dortmund.de
-------

[ these may already have been sent, but i can't find them quickly. ]
Date: 23 Feb 1993 20:17:58 +0100 (MEZ)
From: Joachim Schrod <schrod@iti.informatik.th-darmstadt.de>
Subject: errors in TeXbook

Hi barbara,

isn't this the time DEK works on TeX again? Have you forwarded him
the following errors/problems, which I mentioned to you a year ago?
(All apply to the Oct 89 edition, 9th hardcover printing.)

 ----------------------------------------------------------------------

On p.368 it is specified: ``After ^^ TeX simply adds or subtracts '100
from the character immediately following.'' The example is given with
^^j. Aren't lowercase letters in the range a-f and digits forbidden
due to the new hex input of chars >"7f ?
[ dek:	Page 368 is correct (but not complete).  Page 370 likewise.
	Also you can et p with ^^0 if no hex digit follows (but the
	full rules are on p47)
]

 ----------------------------------------------------------------------

On p.226 it is mentioned that two whatsit-nodes are realized as
extensions to TeX. \language is the third.
[ dek:	Again, page 226 does not claim "two and only two".  Page 455
	mentions the other case.  (I've changed the index entry for
	whatsit, so you win $2.56 for that) p481
]

 ----------------------------------------------------------------------

Exercise 8.7 is printed twice.
[ dek:		(Known)
]

This should be mentioned against AW, not against DEK. It's obviously a
printer's error.
[ dek:	Well, I didn't communicate successfully enough or check it
	well enough
]

 ----------------------------------------------------------------------

Joachim

************************************************************************

>>> The TeX program

    +++ Comments at the top of tex.web / mf.web

Date: Mon, 23 Mar 92 18:04:08 GMT
From: Chris Thompson <CET1@phx.cam.ac.uk>
Subject: A small oversight in MF.WEB 2.71

Barbara,

    Line 23 of mf/mf.web at labrea (i.e. the new official MF 2.71) reads

% Version 2.71 fixed bug in draw, allowed unprintable filenames (not yet released).

I imagine Don forgot to update it when making 2.7a into 2.71 (they are
identical apart from the banner change)! Perhaps someone could draw his
attention to this.

Chris Thompson
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk
-------
(reply, 23 Mar 1992)
chris,
i noticed that too.  similarly in tex.web, in that the date given
is september '91.
-------

 ----------------------------------------------------------------------

    +++ Changes in kerning in 3.141

Date: Thu, 19 Mar 92 15:55:26 GMT
From: Chris Thompson <CET1@phx.cam.ac.uk>
To: Barbara Beeton <BNB@MATH.AMS.COM>,
 Brian {Hamilton Kelly} <TeX@rmcs.cran.ac.uk>
Subject: Bug (?) report on TeX 3.141 by Wayne Sullivan

I have received the following message from Wayne. I am not in a
position to do *any* testing for the next few days, but it sounds
as though he's saying that the bug in TeX 3.14a hasn't been entirely
stopped up in TeX 3.141 (although it did seem to be in 3.14b). Can
anyone check?

> Accepted:  15:25:12 19 Mar 92
> Submitted: 15:04:28 19 Mar 92
> IPMessageId: -unspecified-
> From: "Wayne G. Sullivan" <WSULIVAN@IE.UCD.IRLEARN>
> To: Chris Thompson <CET1@UK.AC.CAMBRIDGE.PHOENIX>
> Subject: TeX 3.141
>
> I got the WEB file for 3.141 and adapted my MS-DOS CHG file: The resulting
> EXE's give no problem with the TRIP test, but as a extra check, I ran off
> my test version of TEXMAN. The DVI file produced by my 3.141 that of
> an '89 version differs at only one point: the index entry for `box memory,'.
> The new version has a kern between the `y' and ',' as there should be for
> cmr8. However, Knuth has made the comma active for the index so that the
> usual inner loop does not insert kerns (there are several instances of
> `y,'). The new DVI file only inserts one kern. Is there something in the
> new mechanism that could cause the tokens to be rescanned in this single
> case so that a kern is inserted? The full entry in the index is
>
>         box memory, 300, 394.
>
> Of course it could be a bug in my new version, but it is hard to see how
> it could cause something like this to happen.
>                     Wayne Sullivan

Chris Thompson
Cambridge University Computing Service
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk
-------
Date: Fri, 20 MAR 92 18:35:49 GMT
Reply-to: Brian {Hamilton Kelly} <TeX@rmcs.cranfield.ac.uk>
From: TEX@rmcs.cranfield.ac.uk
Subject: RE: TeX 3.141

In a message to BHK of Fri, 20 Mar 92 13:03:51 GMT, 
"Wayne G. Sullivan" <WSULIVAN@IE.UCD.IRLEARN> wrote:

> In testing an MS-DOS version of TeX 3.141, I noticed an example where
> the DVI file produced by 3.141 differs from that produced by 3.14. The
> test file I used is over 1 Mbyte, but I have been able to produce the
> same problem in a much smaller file. I thought Knuth always tried to
> make upgrades of TeX downward compatible, so 3.14 and 3.141 should
> not yield different DVI files in this case. It is possible that the
> difference is due to something I have done to my CHG file -- but the
> CHG files for 3.14 and 3.141 are nearly the same. Could you check to see
> whether your VAX versions of TeX produce different DVI files for
> the input file included below?
>  
> %% 3.141 DVI file includes a kern between `y' and `,' in `memory,'
> %%           but not in `display,' .
> %% 3.14  DVI file does not have a kern in either case.
>  
> \let\comma=,%
> \let\period=.%
> \raggedright \tolerance=5000 \hbadness=5000 \parfillskip 0pt plus 3em
> \hsize=17.5pc
> \catcode`\,=\active \def,{\tenrm\comma}
> \catcode`\.=\active \def.{\tenrm\period\par\hangindent 2em }
> \parindent0pt\relax
> box display, 66, 75, 79, 158--159, 302, 455.
> box memory, 300, 394.
> \bye

I can confirm this phenomenon: moreover, the additional kern first
appears at V3.14a, and is also present in V3.14b.  Goodness alone knows
why just this one manifestation occurs in such a huge test file.  The
point is: should DEK fix it?

Brian
PS My mailer ain't very clever: this was REPLYed to Wayne, and copied to
bnb and Chris Thompson
-------
Date: Sun, 22 Mar 92 02:23:46 GMT
From: CET1@phx.cam.ac.uk
To: tex-implementors@MATH.AMS.COM
Cc: Wayne Sullivan <WSULIVAN@IRLEARN.UCD.IE>,
 Brian {Hamilton Kelly} <TeX@rmcs.cran.ac.uk>, Barbara Beeton <BNB@MATH.AMS.COM>
Subject: A feature(?) of TeX 3.141 discovered by Wayne Sullivan

Wayne Sullivan has discovered a situation in which TeX 3.141 gives
different character spacing from TeX 3.14. I think it is probably a
`feature', but maybe it is a `bug': read the following and judge for
yourselves. The change was in fact already present in the alpha test
versions 3.14a and 3.14b, but Brian and I failed to discover it.

Here is Wayne's original report to me

> I got the WEB file for 3.141 and adapted my MS-DOS CHG file: The
> resulting EXE's give no problem with the TRIP test, but as a extra
> check, I ran off my test version of TEXMAN. The DVI file produced by
> my 3.141 that of an '89 version differs at only one point: the index
> entry for `box memory,'. The new version has a kern between the `y'
> and ',' as there should be for cmr8. However, Knuth has made the comma
> active for the index so that the usual inner loop does not insert
> kerns (there are several instances of `y,'). The new DVI file only
> inserts one kern. Is there something in the new mechanism that could
> cause the tokens to be rescanned in this single case so that a kern is
> inserted? The full entry in the index is
>
>         box memory, 300, 394.
>
> Of course it could be a bug in my new version, but it is hard to see
> how it could cause something like this to happen.

and later he provided the following stripped down test case

> Yet a simpler file displaying the problem. With 3.141 one `y,' has no
> kern (display,) while the other does (memory,). 3.14 has no kern for
> both cases.
>
> \let\comma=,%
> \let\period=.%
> \raggedright \tolerance=5000 \hbadness=5000 \parfillskip 0pt plus 3em
> \hsize=17.5pc
> \catcode`\,=\active \def,{\tenrm\comma}
> \catcode`\.=\active \def.{\tenrm\period\par\hangindent 2em }
> \parindent0pt\relax
> box display, 66, 75, 79, 158--159, 302, 455.
> box memory, 300, 394.
> \bye

The fact that the comma is active is significant only in that it
generates a "\tenrm" between the "y" and the ",". This causes TeX
(in |main_control|) to think they are in separate words and so the
usual implicit kern doesn't get generated. There is no change here
in TeX 3.141.

In TeX 3.14 and earlier, if automatic hyphenation was later applied
to the horizontal list, no change was made here. In TeX 3.141, however,
automatic hyphenation re-asseses the relationship between the last
letter of the word and subsequent punctuation, and reinserts the
implicit kern. (TeX 3.141 has changes in this area to fix bugs
associated with right boundary characters, discovered by Brian HK.)
The effect can be demonstrated by a simple test:

    % TeX 3.141 (3.14a,3.14b) test following Wayne Sullivan.
    \ Display\tenrm,\par
    \ Display{}.\par
    \pretolerance=-1 % now force a hyphenation pass
    \ Display\tenrm,\par
    \ Display{}.\par
    \showboxbreadth=255 \showboxdepth=255 \showlists
    \bye

In TeX 3.14 the kerns never reappear, in TeX 3.141 they reappear just
in the last two cases.

Note: I am relying on Wayne and Brian in saying that the effect happens
in TeX 3.141; at the moment I only have 3.14a and 3.14b available. But
I don't believe there is any significant change between 3.14b and 3.141.

Of course, we are used to the fact that TeX's automatic hyphenation
recalculates ligatures and implicit kerns within a word. We know that
it is not sufficient to write `shelf{}ful', but that we must must use
`shelf\/ful' (say) instead. The change in TeX 3.141 extends this state
of affairs slightly. So: `feature' or `bug' ?
[ dek:			  ^^^^^^^
	Chris' explanation is lucid and correct, as usual.  But nobody
	has explained why TeX would try hyphenation for `box memory'
	(the short line) _rather_ than `box display' (the long line)!
	The reason is that the index is typeset with special parfillskip
	that tries to avoid short last lines.  So `box display' turns
	out to meet pretolerance but `box memory' doesn't.  Even more
	interesting is the index entry `beauty, 1.' which spectacularly
	fails to meet pretolerance [badness 2913] yet it does _not_
	gain a kern.  The reason is that TeX finds no hyphenation points
	in `beauty' so does not bother reconstructing its kerns.
	[Please communicate this to Chris and the others.  By the way,
	shelf\-ful is better than shelf\/ful on two counts: (1) it
	hyphenates; (2) it works in italics.]
]

Chris Thompson
Cambridge University Computing Service
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk
-------
Date: Sun, 22 Mar 1992 22:42 GMT +0100
From: Frank Mittelbach <MITTELBACH@MZDMZA.ZDV.UNI-MAINZ.DE>
To: CET1@PHX.CAM.AC.UK, BNB@MATH.AMS.COM, WSULIVAN%IRLEARN.BITNET@vm.gmd.de,
 TEX@RMCS.CRANFIELD.AC.UK
Subject: Re: bug or feature in 3.141

> Note: I am relying on Wayne and Brian in saying that the effect happens
> in TeX 3.141; at the moment I only have 3.14a and 3.14b available. But
> I don't believe there is any significant change between 3.14b and 3.141.

I checked that the effect doesn't happen with 3.14 as distributed by
ArborText so it was most certainly introduced with the last changes.

> Of course, we are used to the fact that TeX's automatic hyphenation
> recalculates ligatures and implicit kerns within a word. We know that
> it is not sufficient to write `shelf{}ful', but that we must must use
> `shelf\/ful' (say) instead. The change in TeX 3.141 extends this state
> of affairs slightly. So: `feature' or `bug' ?

I would vote for feature, not that I like this particular one :-) but
the new behavior seems in my eyes more consistent then TeX's behavior
before. The whole area of loosing information when reconstructing the
horizontal list after hyphenation is something I think is a
(mis)feature since it depends on side effects of other areas.

When one like to call this a bug then only in the respect that \tenrm
interrupts the construction of ligatures or kerns and this fact is not
mentioned in the book (so probably $2.56 :-) or is it?
[ dek:						^^^^^ it is (page 286)
]

Frank

 ----------------------------------------------------------------------

    +++ \language and \setlanguage

Date: 16 Jul 1992 15:23:11 -0300 (BST)
From: Chris Thompson <CET1@phx.cam.ac.uk>
To: Rainer Schoepf <Schoepf@sc.ZIB-Berlin.de>
Subject: Re: [\language and \setlanguage -- the story continues]

Rainer,

   I am copying this reply to Barbara, and for her benefit I will
include your original message here:

> I've just spent some time tracing down a strange behaviour with
> multiple hyphenation patterns. Have a look a the following simple
> file:
>
> ---
> \language=1
>
> \scrollmode
>
> \showhyphens{zwischen}
>
> \setbox1=\hbox{B\"ohme Robert,}
> \setbox0=\hbox{Der Lykomide : Tradition und Wandel
>         zwischen Orpheus und Homer :}
>
> \hsize=10.2cm
> \vsize=7,8cm
>
> \vbox{\unhbox1 \space\unhbox 0}
>
> \eject
>
> \bye
> ---
>
> The hyphenation patterns inside the \vbox are that of \language=0.
> However, if I put one character at the very beginning of the \vbox, it
> uses \language=1.
>
> The reason is rather simple: the procedure new_graf sets the variable
> clang to 0, and it is set to the value of language ony later, when a
> character is contributed to the current list. \unhbox does not change
> the value clang. Of course, I can get around it using \setlanguage.
[ dek:							and \everybox
]
>
> I think this is a bug, since \setlanguage should only be needed when
> working with more than one language. I think new_graf should initialize
> clang to the current value of \language. What do you think?

There is no doubt that the current setup gives favoured treatment to
the \language=0 case. However it certainly wouldn't be right to simply
modify |new_graf| as you suggest. There are three places which have to
be kept consistent:

Module 891: <Initialize for hyphenating a paragraph>
  The value which |cur_lang| is initialised to.
Module 1091: |new_graf|
  The value which |clang| is initialised to.
Module 1200: |resume_after_display|
  The value which |clang| is initialised to.
[ dek:	and consistent with TeXbook p455 on which people have been
	told they can rely.  However, I guess the rule makes absolutely
	no difference in any reasonable application, so i have a chance
	to change page 455.
]

Currently all the initialisations are zero, and therefore consistent.
If modules 1091 and 1200 were to use the value of \language, then this
value has to be remembered somewhere so that module 891 can use it
(clearly the value of \language when module 891 comes to execute
is not what is wanted). Note that the values of \lefthyphenmin and
\righthyphenmin have to be remembered in the vertical mode |nest| entry
*below* the |nest| entry for the paragraph itself, as the latter no
longer exists when module 891 executes.

A possible line to take would be that whenever unrestricted horizontal
mode is started (modules 1091 and 1200), a \setlanguage whatsit should
be automatically generated if \language is non-zero. This would make
these values more like first-class citizens: one could view the special
arrangements for remembering \lefthyphenmin and \righthyphenmin
in |nest| as merely an optimisation for the common case when \language
is zero. But there are potential problems with this: for example, is
the whatsit to be inserted before or after the \everypar tokens are
scanned? If before, the \everypar{\setbox0=\lastbox} mechanism will
no longer work: if after, what if the \everypar does something like
your \unhbox'ing?

Whatever Don may want to do about the above, I think the following is
definitely a bug:

> \language=0 % throughout
> \hsize=1in
> \tracingparagraphs=\maxdimen
>
> \lefthyphenmin=1 \righthyphenmin=1
> This is the moment in time for all good men,
> \lefthyphenmin=2 \righthyphenmin=3 \setlanguage\language
> to come to the assistance of the party.
> $$ x\sp n+y\sp n \ne z\sp n $$
> as Pierre Fermat announced to all and sundry, although he
> couldn't fit the proof into his margin.
>
> \bye

The text after the displayed equation reverts to being hyphenated
with (left,right)hyphenmin=(1,1), even though that immediately before
the equation has (2,3). This is because |resume_after_display| in
module 1200 doesn't set |lhmin| & |rhmin| in the way that module 1091
does, but instead leaves the values set by the original |new_graf|.
I think this is just wrong, even though changing \{left,right}hyphenmin
without changing \language is, perhaps, a rather unusual thing to do.
[ dek:	True; I shall have to fix this in 3.415			$20.48
	And then I have to essentially contradict page 455 because
	I'm resetting clang to 0 after every displayed equation, not
	only at beginning of paragraph.  So the rules stated in
	TeXbook are faulty.
]

Chris Thompson
Cambridge University Computing Service
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk
-------
Date: 16 Jul 1992 17:48:17 +0200
From: schoepf@sc.ZIB-Berlin.DE (Rainer Schoepf)
To: Chris Thompson <CET1@PHOENIX.CAMBRIDGE.ac.uk>
Subject: Re: [\language and \setlanguage -- the story continues]

Chris,

(A copy of this message goes to Barbara.)

 > There is no doubt that the current setup gives favoured treatment to
 > the \language=0 case. However it certainly wouldn't be right to simply
 > modify |new_graf| as you suggest. There are three places which have to
 > be kept consistent:
 > 
 > Module 891: <Initialize for hyphenating a paragraph>
 >   The value which |cur_lang| is initialised to.
 > Module 1091: |new_graf|
 >   The value which |clang| is initialised to.
 > Module 1200: |resume_after_display|
 >   The value which |clang| is initialised to.
 > 
 > Currently all the initialisations are zero, and therefore consistent.

I agree that they are consistent with each other but, in my opinion,
not consistent with the setting of language. The conclusion is that
you cannot globally set language to a value different from 0, since
TeX will sometimes use the hyphenation patterns for language 0.
[ dek:	The intent was to have language 0 be the user's "global"
	language [not to have it be English].  But I guess this
	requires more .fmt files (one for each home language)
]

 > If modules 1091 and 1200 were to use the value of \language, then this
 > value has to be remembered somewhere so that module 891 can use it
 > (clearly the value of \language when module 891 comes to execute
 > is not what is wanted). Note that the values of \lefthyphenmin and
 > \righthyphenmin have to be remembered in the vertical mode |nest| entry
 > *below* the |nest| entry for the paragraph itself, as the latter no
 > longer exists when module 891 executes.

I'd argue that cur_lang should be set to the value of language that
was in effect at the beginning of the paragraph. I haven't thought
this completely through yet, but wouldn't it be just sufficient to set
cur_lang to clang in module 891? When this code is executed, the
semantic nest has already been popped, so that clang is the value that
was in effect just before the call to new_graf. On the other hand, if
there was a change to \language in between, then a setlanguage whatsit
will be present, and cur_lang be set appropriately.

   Rainer Schoepf
   Konrad-Zuse-Zentrum                       ,,Ich mag es nicht, wenn
    fuer Informationstechnik Berlin            sich die Dinge so frueh
   Heilbronner Strasse 10                      am Morgen schon so
   W-1000 Berlin 31                            dynamisch entwickeln!''
   Federal Republic of Germany
   <Schoepf@sc.ZIB-Berlin.de> or <Schoepf@sc.ZIB-Berlin.dbp.de>
-------
Date: 17 Jul 1992 14:38:53 -0300 (BST)
From: Chris Thompson <CET1@phx.cam.ac.uk>
To: Rainer Schoepf <Schoepf@sc.ZIB-Berlin.de>
Subject: Re: [\language and \setlanguage -- the story continues]

Rainer (& Barbara),

> I agree that they are consistent with each other but, in my opinion,
> not consistent with the setting of language. The conclusion is that
> you cannot globally set language to a value different from 0, since
[ dek:^^^^^^^^^^^^^^^
	you can just say \everyhbox{\setlanguage 1}
	(Agreed that this is not 100% efficient!)
]
> TeX will sometimes use the hyphenation patterns for language 0.

I wasn't saying (I think) that they shouldn't be changed, just that
they need to be changed consistently.

> I'd argue that cur_lang should be set to the value of language that
> was in effect at the beginning of the paragraph. I haven't thought
> this completely through yet, but wouldn't it be just sufficient to set
> cur_lang to clang in module 891? When this code is executed, the
> semantic nest has already been popped, so that clang is the value that
> was in effect just before the call to new_graf. On the other hand, if
> there was a change to \language in between, then a setlanguage whatsit
> will be present, and cur_lang be set appropriately.

No, this is confused. |clang| is part of the |aux| field in a |nest|
entry, and is only defined when the mode is horizontal. The current
mode is vertical when module 891 is executing. Notice how |lhmin| and
|rhmin| are set *before* the |push_nest| in |new_graf|, while |clang|
is set *after*.

The |lhmin| and |rhmin| fields exist in every |nest| entry (although
only used in a few). It would be perfectly possible to add a new field
to the structure to save the initial \language value, in the same way:
this would be the cleanest thing to do and I should have mentioned it.
But it would mean increasing the size of each |list_state_record|.

 --- Pause ---

Ah ha! There is something one could do to achieve this effect *without*
increasing the size of |list_state_record|, and indeed reclaiming the
2 quarterwords |lhmin| and |rhmin| that were added to it in TeX 3.0. The
|prev_graf| field exists in all |nest| entries but contains meaningful
information only for those with vertical mode. Use a redefinition of
this field for the unrestricted horizontal mode entry to hold the
*initial* values of \lefthyphenmin, \righthyphenmin, *and* \language
in |new_graf| and |resume_after_display|; they would fit easily enough.
Then break the values out into local variables in |line_break| *before*
the |pop_nest| (module 816), so that they are available to module 891.

I rather like this scheme.

Chris Thompson
Cambridge University Computing Service
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk
-------
[ dek:	OK, it's in.
	No advantage to the old rule and no reason to assume anybody
	made use of it in ways that are incompatible with the new one.
]

 ----------------------------------------------------------------------

    +++ Cramped style inconsistencies

[ i forwarded this to chris thompson, but received no reply. ]
Date: 17 Sep 1992 14:06:57 -0400 (EDT)
From: herschor@math.mcgill.ca (Michael Herschorn)
To: BNB@MATH.AMS.ORG
Subject: Is it a bug?

On July 21 I sent the appended lengthy submission to Info-Tex, and 
it was automatically posted to comp.text.tex on the net. (Because of 
its length, I do not use the standard quotation indicators.)

I have received no comments; maybe that's because it's much ado 
about not very much. (Since I'm a relative newcomer to TeX, it may also
be because I'm totally "off-track".) Nevertheless, there's at least one 
part of the submission that you are best placed to give an opinion on. It 
reads:

: (I also haven't come across any discussion of a "feature" which turns
: cramping off, viz., prefix the material which TeX would normally
: cramp by an explicit style reminder. Compare, for example,
: $\sqrt{X^2+Y^2}$ with $\sqrt{\textstyle X^2+Y^2}$. However, I doubt
: that this is an intended feature since:
: i) TeX is normally insensitive to redundant style commands, and from
: the user's point of view, this is the way it should be; and,
: ii) cramping will be turned off in midstream by an explicit style
: command (e.g., $\sqrt{X^2+\textstyle Y^2} has X^2 in cramped style
: and Y^2 in uncramped style).
: I am completely out of my depth when it comes to understanding the
: details of The Program, and please, no flames (not even for the
: mixing of metaphors!), but it seems to me that this "feature"
: is a result of the cramped_style calculation in section 702 of The
: Program being ignored while section 703 updates only size-dependent
: quantities.
: Although I reserve my rights to priority for the "finder's fee"
: mentioned in the Preface to The Program, I would like to hear the
: opinions of gurus on the net.)

I would greatly appreciate your comments on these paragraphs, and if 
you care to, on the rest of the posting.

Michael Herschorn

[ dek:	TeX should have had a primitive something like `\cramp' to force
	a cramped style, but it's too late now.  TeX shouldn't preserve
	crampedness when \textstyle comes along because then there's
	no way to override it...  well I guess one could use \hbox but
	again it is too late to make changes.
]


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%%               July 21, 1992 Posting
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Newsgroups: comp.text.tex
Date: Tue, 21 Jul 92 12:25:00 EDT
Organization: Info-Tex<==>Comp.Text.Tex Gateway
From: herschor@math.mcgill.ca (Michael Herschorn)
Subject: CRAMPED STYLES & solution to:fraction spacing default_rule_thickness.
Lines: 374

 At the end of this submission you will find a solution to the
 problem relating to the minimum separation between the numerator or
 denominator of a fraction and the fraction bar, a question raised and
 discussed in several postings last month. I would like
 to begin with a more general problem which provides the tool
 used for that solution.

 PART ONE:

 To measure typeset text from a math list in TeX, the material is
 placed in an \hbox. One must then specify the style of
 the text's "free state" inside the box. The horizontal dimension in
 the free state is affected by "actions at infinity" (glue) and is
 intrinsically uncertain; the height and depth are determined
 "quasi-locally", and are fixed once TeX decides on the current style.
 However, if an item is to be set in a cramped style, absent a TeX
 command \cramp{}, how does one measure its height and depth?

 I have also felt a need for \cramp for aesthetic reasons when there
 is a repetition of an expression close by the original in a line of
 text, once in 
an uncramped style, and once in the corresponding
 cramped style. As well, there is a not insignificant amount of space
 that can be saved in a document with multiple occurrences of, e.g.,
 ${\x}^{{\x}^{{\x}^{\cdot^{\cdot^{\cdot^{\x}}}}}}$, if this could
 be set in a cramped style.
[ dek:	For such a document I would fiddle with parameter \sigma_14
]

 I have most of the standard TeX references, but I haven't come across
 any mention of the possibility of obtaining a cramped style "on
 demand". Thus there may be some general interest in the preliminary
 version of my <cramped.sty> macro, and I append it below.

 (I also haven't come across any discussion of a "feature" which turns
 cramping off, viz., prefix the material which TeX would normally
 cramp by an explicit style reminder. Compare, for example,
 $\sqrt{X^2+Y^2}$ with $\sqrt{\textstyle X^2+Y^2}$. However, I doubt
 that this is an intended feature since:
[ dek:	It is "intended" in the sense that it is rule 3 on page 442
]
 i) TeX is normally insensitive to redundant style commands, and from
 the user's point of view, this is the way it should be; and,
 ii) cramping will be turned off in midstream by an explicit style
 command (e.g., $\sqrt{X^2+\textstyle Y^2} has X^2 in cramped style
 and Y^2 in uncramped style).
 I am completely out of my depth when it comes to understanding the
 details of The Program, and please, no flames (not even for the
 mixing of metaphors!), but it seems to me that this "feature"
 is a result of the cramped_style calculation in section 702 of The
 Program being ignored while section 703 updates only size-dependent
 quantities.
 Although I reserve my rights to priority for the "finder's fee"
 mentioned in the Preface to The Program, I would like to hear the
 opinions of gurus on the net.)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% cramped.sty    Preliminary version           July 21,1992
%
% Enables the typesetting of material in the cramped styles
% D', T', S' and SS'.
%
% \cramp{<foo.bar>} will set <foo.bar> in the cramped version C' of
% the current style C.
%
% \Cramp{\...style}{<foo.bar>} (where you specify the current style)
% has been left accessible.
%
%
% Author: Michael Herschorn
%         Departmentof Mathematics and Statistics
%         McGill University
%         805 Sherbrooke Street West               Phone: 514-398-3825
%         Montreal QC  CANADA  H3A 2K6               FAX: 514-398-3899
%         email: herschor@gauss.math.mcgill.ca
%
% Please email me your comments and suggestions as well as informing
% me directly of any bugs you may find.
%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\catcode`@=11
\def\cramp{\mathpalette\Cramp}%
\def\Cramp#1#2{\setbox0=\hbox{$\m@th#1\cr@mp{#2}$}
% [ dek:  As an alternative, you could reset \nulldelimiterspace here
% ]
     \Ch@p#1 \dimen2=\the\ht0 \advance\dimen2 -\dimen0
     \ht0=\the\dimen2 \box0}
\def\cr@mp{\kern-\the\nulldelimiterspace\radical"380380}%
% [ dek:					^^^^^^^
%		nonexistent characters; better to say \radical 0
% ]
\def\Ch@p#1{\ifx#1\displaystyle
    \dimen0=\the\fontdimen5\textfont2
    \advance\dimen0 -.75\dimen0
% [ dek:  why not say \dimen0=.25\fontdimen5\textfont2
% ]
    \advance\dimen0\the\fontdimen8\textfont3
  \else
%%    \ifx#1\textstyle
    \dimen0=\the\fontdimen8\textfont3
    \advance\dimen0 .25\dimen0
 \fi}%%%%%%%%% If you have "variations" in family 3,
%%%%%% comment out the preceding line and "uncomment"
%%%%%% the 7 lines beginning with "%%".
%%  \else
%%    \ifx#1\scriptstyle\dimen0=\the\fontdimen8\scriptfont3
%%    \advance\dimen0 .25\dimen0
%%  \else \dimen0=\the\fontdimen8\scriptscriptfont3
%%    \advance\dimen0 .25\dimen0
%%  \fi\fi\fi}
\catcode`@=12
\endinput
%%
% end of file cramped.sty
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[ dek:	The same idea
	but using TeX more fluently:
	\def\Cramp#1#2{\setbox0=\hbox{\nulldelimiterspace=\z@
				@\m@th#1\radical0{#2}$}%
	    \ifx#1\displaystyle
		\dimen0=\fontdimen8\textfont3
		\advance\dimen0 .25\fontdimen5\textfont2
	    \else \dimen0=1.25\fontdimen8
		\ifx#1\textstyle\textfont
		\else\ifx#1\scriptstyle\scriptfont\else\scriptscriptfont
		    \fi\fi 3 \fi
	    \advance\dimen0-\ht0 \ht0=-\dimen0 \box0 \relax}

	(He uses \the' unnecessarily and doesn't factor \if...\fi)

	This works.  (worth publishing in TUGboat)
	----
	Note that \cramp{x^{\cramp{y^2}}}
	causes TeX to typeset y^2 16 times!
	The same is true whenever a \mathpalette is inside a \mathpalette
]


 PART TWO:

 Michael Downes <MJD@MATH.AMS.COM> (22 Jun 1992, Info-TeX@shsu.edu)
 wrote:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+Dan Luecking wrote (19 Jun 1992, Info-TeX@shsu.edu):
+
+> Michael Barr posted a query a while back about the separation
+> between the numerator/denominator of a fraction and the fraction bar.
+>
+> I have not seen a response, so having tried to understand the
+> TeXbook on this point and made some headway in doing so I thought
+> I might discuss the problem.
+
+> ... I have run into it several times and would like to know if
+> anyone has defined a fraction making command to deal with it. One
+> way is to insert a 0 width rule extending below the numerator and
+> above the denominator, but I do not see a good way to make this
+> automatic. A way I have considered, but rejected, is to increase the
[ dek:		clever thought
]
+> relevant parameter, (something like \fontdimen8\textfont3=1pt
+> instead of 0.4pt) and then define all \frac's using \above (in which
+> the thickness of the rule is explicitly given). The problem is that
+> default_rule_thickness is used in several internal calculations
[ dek:	\overline is screwed up but could be handled as special kind
	of \radical (with new font)!
]
+> including the positioning of sub/superscripts.
[ dek:	rule 18e, not too bad if increased
]
+>
+> Does anybody have anything to say about this?
+
+  I have observed the same problem in Amer. Math. Soc. publications,
+  although the examples I've happened to notice involved letters with
+  descenders such as p and q, rather than vertical bars. Your analysis
+  of the problem corresponds closely to what I found in some cursory
+  investigations.
+
+  The problem seems to be slightly worse than you suggest---or maybe you
+  just didn't bother to amplify on results of your experiments: The most
+  significant drawback of the rejected solution of setting \fontdimen 8
+  \textfont 3 to a larger value and using \above instead of \over is
+  not the internal calculations you mention but the fact that the fraction
+  bar thickness and the space around it are always dependent, even in
+  \above, so that if we say $1\above.4pt 2$ the space around the
+  fraction bar is calculated from the .4pt, not from \fontdimen 8 of
+  \textfont 3, and we're back where we started from.
[ dek:					Oh, right!
]
+
+> ... Is it worthwhile suggesting
+> that a major macro package try do something about it? Have any done
+> anything?
+
+  If my understanding of the problem is correct, it's impossible for a
+  macro package to provide any reasonable solution. The only reasonable
+  solution is to change TeX, the program. (And my definition of
+  `reasonable' is pretty extreme when it comes to macro writing; I have
+  done or contemplated doing things at the macro level that any
+  `reasonable' programmer would consider unreasonable.)
+
+> Is there any real problem at higher resolutions (i.e., does
+> everything look OK printed at 1000dpi)?
+
+  In my opinion, there is not enough space around the fraction bar in
+  the problematic combinations (textstyle fractions, vertical bars,
+  letters with descenders), even at high resolution. I'd rather have
+  some control to adjust the space slightly.
[ dek:	For these you are probably best off tuning the \sigma's...
	although it's probably OK to teach keyboarders what I actually
	do 	[see next comment]
]
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 The Grand Wizard made his design choices a.e. optimally, and I would
 stick with his implementation of 15d in Appendix G of The  TeXbook.
 Apparent differences between the letter-base levels in the numerators
 and in the denominators of fractions in the same line spoil the
 appearance of the line; shifting the numerator up or the denominator
 down in a fraction with adequate clearance so as to match the letter-
 base levels of another fraction in the line introduces ugly white
[ dek:	I am occasionally unhappy with fractions, much more often
	unhappy with \root's, and guilty of overlooking several
	fontdimens in false belief that I was getting more
	unity/elegance.  So I occasionally use ^{\mathstrut} in
	denominators (or superscripts therein), often in \root's,
	_{\mathstrut} in numerators (or subscripts therein).
]
 space.  The more I understand the problem, the better I like the GW's
 balancing act.

 Nevertheless, as pointed out by Dan Luecking, Berthold K.P. Horn and
 Michael Downes, it would have been nice to have a free parameter to
 adjust in special circumstances. ("Just so you shouldn't need to
 use it", as the Yiddish expression puts it.)

 Once we have <cramped.sty>, it becomes a simple hack to solve this
 problem (and other similar ones). I wrote (and attach a copy of)
 <spreadfraction.sty> as an illustration. (The coding is not elegant,
 but it works.) It should be used only when absolutely necessary,
 and even then, it should be used sparingly.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% spreadfraction.sty        Preliminary version           July 21,1992
%
% If used in a non-cramped context, \xfrac{#1}{#2}{#3} produces
% {#1\over #2} exactly as TeX would, except that the minimum clearance
% that will be tolerated between the numerator or denominator of this
% fraction and the bar line is #3 times the default rule thickness.
% (See Rule 15d in Appendix G of The TeXbook. TeX hardwires in
% #3=3 in \displaystyle and #3=1 in the other styles; spreadfraction.sty
% allows the use of arbitrary values. In other words, .phi. is replaced
% by #3 times the default rule thickness, everything else is kept
% constant.)
%
% In a cramped context, i.e., if the entire fraction is a Rad atom
% (under a root sign), an Over atom (from \overline), in the denominator
% of another fraction, is a subscript, or is a superscript to an
% entity in cramped style, \xfracc{#1}{#2}{#3} should be used instead
% of \xfrac{#1}{#2}{#3}. (I may automate the selection of \xfracc in a
% future version; since spreadfraction.sty is intended for touch-up use,
% I don't consider automation a priority (and it may be like putting a
% tiara on a baglady!)).
%
% \Xfrac{\...style}{}{}{} (identical to \xfrac{}{}{}, except
% that you specify the style) and \Xfracc{\...style}{}{}{} (DITTO),
% have been left accessible to the user.
%
% To obtain a version of spreadfraction in which the minimum clearances
% are #3 times the hardwired ones, declare \DEKtrue after inputting
% spreadfraction.sty
%
%
% Author: Michael Herschorn
%         Departmentof Mathematics and Statistics
%         McGill University
%         805 Sherbrooke Street West               Phone: 514-398-3825
%         Montreal QC  CANADA  H3A 2K6               FAX: 514-398-3899
%         email: herschor@gauss.math.mcgill.ca
%
% Please email me your comments and suggestions as well as informing
% me directly of any bugs you may find.
%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\newif\ifDEK
\input cramped.sty
\catcode`@=11
\def\xfrac#1#2#3{\M@thpalette\Xfrac{#1}{#2}{#3}}
\def\M@thpalette#1#2#3#4{%
       \mathchoice{#1\displaystyle{#2}{#3}{#4}}%
        {#1\textstyle{#2}{#3}{#4}}%
        {#1\scriptstyle{#2}{#3}{#4}}%
        {#1\scriptscriptstyle{#2}{#3}{#4}}}
\def\Xfrac#1#2#3#4{\ifx#1\displaystyle
       \def\C@rr@ntF@nt{\textfont}
        \let\@djSt@le=\textstyle
         \L@rgeS@ze#1{#2}{#3}{#4}
          \else
           \ifx#1\textstyle \def\C@rr@ntF@nt{\textfont}
            \let\@djSt@le=\scriptstyle
             \N@rmalS@ze#1{#2}{#3}{#4}
          \else
           \ifx#1\scriptstyle
            \def\C@rr@ntF@nt{\scriptfont}
             \let\@djSt@le=\scriptscriptstyle
              \N@rmalS@ze#1{#2}{#3}{#4}
          \else
            \def\C@rr@ntF@nt{\scriptscriptfont}
             \let\@djSt@le=\scriptscriptstyle
              \N@rmalS@ze#1{#2}{#3}{#4}
           \fi
         \fi
       \fi}
\def\L@rgeS@ze#1#2#3#4{\dimen1=\the\fontdimen8\textfont2
              \dimen2=\the\fontdimen11\textfont2
              \N@mer@tor#1{#2}{#3}{#4}}
\def\N@rmalS@ze#1#2#3#4{%
              \dimen1=\the\fontdimen9\C@rr@ntF@nt2
              \dimen2=\the\fontdimen12\C@rr@ntF@nt2
              \N@mer@tor#1{#2}{#3}{#4}}
\def\N@mer@tor#1#2#3#4{%
              \dimen3=\the\fontdimen22\C@rr@ntF@nt2
              \dimen4=\the\fontdimen8\C@rr@ntF@nt3
              \dimen5=#4\dimen4
       \ifDEK\ifx#1\displaystyle\advance\dimen5 2\dimen5
           \else
         \fi
           \else
          \fi
              \advance\dimen4 -.5\dimen4
              \setbox1=\hbox{$\m@th\@djSt@le{#2}$}
              \dimen0=\dimen1 \advance\dimen0 -\the\dp1
              \advance\dimen0 -\dimen3
              \advance\dimen0 -\dimen4
       \ifdim\dimen5>\dimen0 \advance\dimen1 \dimen5
              \advance\dimen1 -\dimen0
              \D@nomin@tor#1{#3}
           \else
              \D@nomin@tor#1{#3}
        \fi}
\def\D@nomin@tor#1#2{%
              \setbox2=\hbox{$\m@th
              \@djSt@le\Cramp\@djSt@le{#2}$}
              \dimen0=\dimen2 \advance\dimen0 \dimen3
              \advance\dimen0 -\the\ht2
              \advance\dimen0 -\dimen4
        \ifdim\dimen5>\dimen0 \advance\dimen2 \dimen5
              \advance\dimen2 -\dimen0 \Qu@ti@nt#1
            \else
             \Qu@ti@nt#1
       \fi}
\def\Qu@ti@nt#1{%
         \ifdim\wd1<\wd2 \dimen9=\the\wd2
               \setbox3=\hbox to \the\dimen9{%
               $\m@th\hfil\box1\hfil$}
               \setbox1=\box3  \dimen8=\dimen9
         \else \dimen9=\the\wd1
               \setbox3=\hbox to \the\dimen9{%
               $\m@th\hfil\box2\hfil$}
               \setbox2=\box3
         \fi
               \advance\dimen1 -\the\dp1
               \advance\dimen1 -\dimen3
               \advance\dimen1 -\dimen4
               \dimen6=\dimen2 \advance\dimen6 -\the\ht2
               \advance\dimen6 \dimen3
               \advance\dimen6 -\dimen4
               \kern\the\nulldelimiterspace
               \raise-\the\dimen2 \hbox to\the\dimen9{%
               \vbox{\box1\kern\the\dimen1\hrule
               \kern\the\dimen6\box2}}
               \kern\the\nulldelimiterspace}
\def\Xfracc#1#2#3#4{\ifx#1\displaystyle
        \let\@djSt@l@=\textstyle
         \G@toResult{#1}{#2}{#3}{#4}
      \else
        \ifx#1\textstyle \let\@djSt@l@=\scriptstyle
         \G@toResult{#1}{#2}{#3}{#4}
      \else
           \let\@djSt@l@=\scriptscriptstyle
            \G@toResult{#1}{#2}{#3}{#4}
           \fi
        \fi}
\def\G@toResult#1#2#3#4{%
           \Xfrac#1{\Cramp\@djSt@l@{#2}}{#3}{#4}}
\def\xfracc#1#2#3{\mathchoice
      {\Xfrac\displaystyle{\Cramp\textstyle{#1}}{#2}{#3}}%
      {\Xfrac\textstyle{\Cramp\scriptstyle{#1}}{#2}{#3}}%
      {\Xfrac\scriptstyle{\Cramp%
       \scriptscriptstyle{#1}}{#2}{#3}}%
      {\Xfrac\scriptscriptstyle{\Cramp%
          \scriptscriptstyle{#1}}{#2}{#3}}}
\catcode`@=12
\endinput
%%
%% end spreadfraction.sty
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 I would appreciate comments and feedback by email and shall
 summarize and post.

 Michael Herschorn

***********************************************************************

 Michael Herschorn                  email:herschor@gauss.math.mcgill.ca
 Department of Mathematics and Statistics             fax: 514-398-3899
 McGill University                                  phone: 514-398-3825
 805 Sherbrooke Street West
 Montreal QC CANADA  H3A 2K6

***********************************************************************

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%%              End of July 21, 1992 Posting
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-------
Date: 29 Jan 1993 02:29:26 -0500 (EST)
From: herschor@math.mcgill.ca (Michael Herschorn)

My understanding is that February is the month in which you present
DEK with a list of possible bugs for his consideration.

Since February is almost upon us, I would like to draw your
attention to our previous e-mail exchanges [ ... ]

Perhaps the simplest thing would be to typeset
$${1\over x^2}{1\over\textstyle x^2}$$
$${1\over X^2}{1\over\textstyle X^2}$$
and look closely at the positioning of the exponents in the denominators
(and the denominators themselves).

TIA

Michael Herschorn

************************************************************************

>>> plain.tex (includes one possible TeX bug)

Date: Sun, 10 May 92 15:33:59 EDT
From: "Walter D. Neumann" <neumann@function.mps.ohio-state.edu>
Subject: plain.tex bugs

Dear Barbara,

In creating a style file for a proceedings volume, Larry Siebenmann
and I had collected various plain.tex bugs and written them at various
times to the net, assuming they would find their way to Knuth and be
corrected eventually.  Checking the most recent plain.tex I see some
have (missing m@th in some macros) but others havn't.  Larry suggested
that you are a good clearing house for this sort of thing, so I am
sending our residue to you.  The bugs are in Plain's handling of
inserts.  One bug is actually a TeX bug, and I havn't checked if most
recent TeX fixes it, since we don't have the most recent installed
yet.  That bug is that \lastskip gets lost by an \insert.  For details
[ dek:	   ^^^	not really a bug in \TeX
]
of this, and also the plain.tex problems, see the following file that
I posted to the net about a year ago.  

In my opinion, items 2 (second part), 3, and 5 of the list of
"problems" deserve the name "bugs" while 2 (first part), 1, and 4 are
merely poor choices.

It also seems to me that it is not logical that TeX uses \topskip
instead of \baselineskip at top-of-page if there is a top insertion
("remaining problem" quoted below).  Bug or poor choice? -- take your
pick.

%% newinsert.tex  3/17/91, 4/2/91 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% walter neumann (neumann@mps.ohio-state.edu)
%
% Include with "\input newinsert.tex" to fix following problems
% with plain TeX's handling of \midinsert and \topinsert:
%
% 1. An insert that falls at the top of the page is too high: it's
%    top is at top-of-page rather than top-of-ink.
% 2. Plain uses \bigskip for space around inserts and assumes \bigskip
%    is 12pt plus stretch, so \midinsert misbehaves if \bigskipamount
%    is changed. This space should be an independent quantity.
% 3. Consecutive midinserts that did not float are spaced twice
%    as far apart as consecutive topinserts or floated midinserts.
% 4. Midinserts can get out of order (see Exercise 15.5 of TeXbook).
% 5. \removelastskip fails after a floated insert. This is relevant for
%    an insertion before any construction (such as a proclamation in
%    plain TeX) that does an explicit or implicit \removelastskip.
%
% Remaining problem: TeX uses \topskip instead of \baselineskip for the
% first line of a page after any topinserts. With the default values
% of 10pt and 12pt respectively, this gives 2pt less space between a
% topinsert or floated midinsert and following text than between a 
% middle insertion and following text. To avoid this use:
%
% \topskip=\baselineskip
% [ dek:	the \skip<n> parameter for \insert<n> handles such
%		discrepancies; see pp 122-123 especially Step 1 on page 123
% ]
%
% PARAMETERS:
% Plain.tex puts \bigskipamount of space before and after inserts.
% We provide \insertskipamount for this purpose (default \medskipamount).
% In addition, \inserthardskipamount of glue is added at the top of EVERY
% insert; it remains even at top of page (default 6pt; it should be at
% least \topskipamount-(text height)).
%   These defaults give good balance for figure insertions of the form:
%       \midinsert
%       [Commands to include a graphics file]
%       \medskip \centerline{Figure Title}
%       \endinsert.
%
\chardef\newinsCatAt\the\catcode `\@
\catcode `\@=11
%
%%%%%%%%%%%% Corrected insert macros for plain.tex %%%%%%%%%%%%%%%%%
%
%  New skipamounts:
%
\newskip\insertskipamount\newskip\inserthardskipamount
\insertskipamount\medskipamount         % Change as desired.
\inserthardskipamount 6pt               % Change as desired (see above)
\def\insertskip{\vskip\insertskipamount}
%
%  Save and restore \lastskip:
%
\newskip\LastSkip
\def\SaveLastSkip{\LastSkip\lastskip}
\def\RestoreLastSkip{\nobreak\vskip-\LastSkip\vskip\LastSkip}
%
%  Larry Siebenmann's test for split topinserts:
%
\newcount\SplitTest%        will be set to -1 if a topinsert has split
\def\SetSplitTest{\SplitTest\insertpenalties
  \SaveLastSkip\insert\topins{\floatingpenalty1}\RestoreLastSkip
  \advance\SplitTest-\insertpenalties}
%
%  From here on we modify definitions in plain.tex.
%
% Redefine \midinsert to convert to \topinsert if a topinsert has been
% split, to prevent midinserts getting out of order (cf. TeXbook Exercise
% 15.5). As in plain.tex, a \midinsert still converts to a \topinsert
% (which then splits) if the insert is too big for current page.
%   Was:    \def\midinsert{\@midtrue\@ins}
\def\midinsert{\par\SetSplitTest\ifnum\SplitTest=-1
% [ dek:	would <0 also work?
% ]
  \@midfalse\else\@midtrue\fi\@ins}
% Redefine \@ins to add \inserthardskipamount of glue above.
%   Was:  \def\@ins{\par\begingroup\setbox\z@\vbox\bgroup}
\def\@ins{\par\begingroup\setbox\z@\vbox\bgroup%
  \vglue\inserthardskipamount}
% Changes to \endinsert of plain.tex 3.0:
% - Use \insertskipamount instead of \bigskipamount throughout.
% - Use larger of previous skip and insertskip before middle insert.
% - Add \nointerlineskip to avoid unwanted extra 1pt skip.
% - Save and restore lastskip when an insert floats.
\def\endinsert{\egroup % finish the \vbox
  \if@mid \dimen@\ht\z@ \advance\dimen@\dp\z@
    \advance\dimen@\insertskipamount%            was 12pt (wn)
    \advance\dimen@\pagetotal\advance\dimen@-\pageshrink
    \ifdim\dimen@>\pagegoal\@midfalse\p@gefalse\fi\fi
% Next 3 lines replace:  \if@mid \bigskip\box\z@\bigbreak (wn)
  \if@mid%
    \ifdim\lastskip<\insertskipamount\removelastskip\insertskip\fi
    \nointerlineskip\box\z@\penalty-200\insertskip
  \else%
    \SaveLastSkip%                                  added (wn)
    \insert\topins{\penalty100 % floating insertion
    \splittopskip\z@skip
    \splitmaxdepth\maxdimen \floatingpenalty\z@
    \ifp@ge \dimen@\dp\z@
    \vbox to\vsize{\unvbox\z@\kern-\dimen@}% depth is zero
    \else \box\z@\nobreak\insertskip\fi}% was \bigskip\fi (wn)
    \RestoreLastSkip%                               added (wn)
   \fi\endgroup}
%%%%%%%%%%%%%%%%%% Done correcting insert macros %%%%%%%%%%%%%%%%%%%
%
\catcode `\@=\newinsCatAt
\endinput
%% end newinsert.tex
 
 -- 
 Walter Neumann              Email:    neumann@mps.ohio-state.edu
 Department of Mathematics                  neumann@ohstpy.bitnet
 Ohio State University       Tel: 614-292-4886 (office)
 Columbus, OH 43210           -292-4975(Math. Dept.) -292-1479 (Dept. Fax)
-------
[ dek:	These macros look very good but I cannot change plain TeX
	any more at this late date.  _Ever_._
	(Wish I had thought of them in 1985!)
	He should publish them in TUGboat.
]

************************************************************************

Date: 24 Feb 1993 17:35:03 -0500 (EST)
From: bbeeton <BNB@MATH.AMS.ORG>
Subject: message for don -- trip, volume b glitch

[ don --
  i don't know why i failed to send this one out with the rest; it's
  not as if it would have taken a long time to edit out extraneous
  stuff.
]

>>> Volume B; trip

Date: Fri, 10 Apr 92 13:21:27 GMT
From: Peter Breitenlohner <PEB%DM0MPI11.BITNET@vm.gmd.de>
Subject: message to DEK

barbara, can you please forward the following to Knuth.  Thanks

1. deficiency in TRIP test.
   while doing some optimization for PubliC TeX I had introduced
   a bug in the splittopskip computation in prune_page_top
   In mod.969 the line
      ....... width(temp_ptr):=width(temp_ptr)-height....
   was changed by mistake to something equivalent to
      ....... width(temp_ptr):=width(temp_ptr)+height....
[ dek:	It would be interesting to check the archives to see why
	we failed to cover this -- but I haven't time to do so
	(nor to update trip).
]
   When this bug was finally found by Ulrik Vieth we both
   were much surprised that this error was never detected by
   the TRIP test!

2. missing mini-index entry
   On page 483 of Vol.B there ought to be an entry for off_save.
   In my old book (TeX Version 2.0) there is none. Unfortunately
   I had no possibility to check one of the newer editions.
[ dek:	the newer books have improved indexing software, so this
	should no longer be an issue.  In 1994, get a new Vol B!
	It will be the permanent, good one.
]

Sincerely   Peter Breitenlohner

************************************************************************

>>> Report on TeX 3.14b

Date: Wed, 5 FEB 92 21:57:11 GMT
Reply-to: Brian {Hamilton Kelly} <TeX@rmcs.cranfield.ac.uk>
From: TEX@rmcs.cranfield.ac.uk
To: BNB <@nsfnet-relay.ac.uk:BNB@MATH.AMS.com>
Subject: RE: TeX 3.14b, etc

barbara,

In message <A5343AE79E00E880@UK.AC.CAMBRIDGE.PHOENIX>  of Wed, 05 Feb 92
17:32:30 GMT, Chris Thompson <CET1@UK.AC.CAMBRIDGE.PHOENIX> wrote:

> Some rather hasty and incomplete testing done. I have compiled
> TeX 3.14b and confirmed that it fixes the doubled kern problem
> in 3.14a, and also Robert Hunt's \showbox bug. Test documents
> generate unaltered DVI files.

I can also confirm that it DOES fix my original problem with terminal-
\sigma ligatures with punctuation.  I've also run TRIP and match DEK's
output (apart from the fact that he's obviously gone the whole hog and
called his executable 3.141, because that's how his logs read, rather
than 3.14b.

> MF 2.7a compiled and run through a few tests. Proof mode cmr10
> shows a diff on character "Q" only: this is presumably the result
> of the "fixed bug in draw" (as there is no new mf84.bug in /alpha,
> I don't know what this bug might be). Actually the pixel deltas
> seem to change the "Q" bitmap back to what it was in some earlier
> version of MF (or maybe this is an accident due to some nearly half
> integral coordinate that flips one way of the other on lots of
> changes).

I haven't looked at MF at all yet, mainly because I didn't know what it
was supposed to be fixing!

> Weave 4.4 compiled and tested to the extent of that it generates
> identical output to 4.2 for a few WEB files.

And I can also confirm that it correctly handles wrapped TeX comments;
great!

> I note the existence of a number of changed .mf files for cm fonts
> in /alpha, but as there is no cm85.bug either, I wouldn't know what
> to look for.

Ditto.

Best regards,

Brian
-------
Date: Thu, 06 Feb 92 13:59:36 GMT
From: Chris Thompson <CET1@phoenix.cambridge.ac.uk>
To: Brian {Hamilton Kelly} <TeX@rmcs.cranfield.ac.uk>,
 Barbara Beeton <BNB@MATH.AMS.COM>
Subject: RE: TeX 3.14b, etc

I have also run the new trip and trap tests (snap!) and they pass
(as Brian points out, in the tr(i|a)p test output the banners appear
as "3.141" and "2.71" rather than "3.14b" and "2.7a"). MF 2.7a passes
the 2.7 trap test; TeX 3.14b doesn't quite pass the 3.14 trip test, but
that is no suprise.

Chris Thompson
Cambridge University Computing Service
JANET:    cet1@uk.ac.cam.phx
Internet: cet1@phx.cam.ac.uk

************************************************************************

>>> tangle.web 4.2

Date: Mon, 24 Feb 92 10:42:31 GMT
From: Peter Breitenlohner <PEB%DM0MPI11.bitnet@CUNYVM.CUNY.EDU>
To: Barbara Beeton <bnb@MATH.AMS.COM>
Subject: tangle.web 4.2

barbara,
I retrieved tangle.web 4.2 from labrea.
To my surprise I found that the 'extra "}" bug' I reported some
time ago ist still there, although it was fixed in weave.
Maybe you can clarify this.
peter
%--------------------------------------
Line numbers refer to TANGLE.WEB 4.2 as of March 26, 1991.

@x [13] m.145 l.2664 get_next - bug fix
othercases if c>=128 then goto restart {ignore nonstandard characters}
@y
"}": begin err_print('! Extra }'); goto restart;
@.Extra \}@>
  end;
othercases if c>=128 then goto restart {ignore nonstandard characters}
@z
%---------------------------------------
-------
Date: Mon, 24 Feb 92 15:45:56 GMT
From: Peter Breitenlohner <PEB%DM0MPI11.bitnet@CUNYVM.CUNY.EDU>
To: Barbara Beeton <bnb@MATH.AMS.COM>
Subject: tangle.web 4.2

barbara,
I forgot to mention another longstanding bug? in tangle:

% TANGLE.WEB 4.2 as of March 26, 1991.

@x [4] m.31 l.642 - activate debug_help
@!debug debug_help;@+gubed
@y
@!debug debug_skipped:=debug_cycle;debug_help;@+gubed
@z
%---------------------------------------
[ dek:	I don't know why version 4.2 was still on labrea; version 4.3
	was released September 1991 and fixed the bug in question ...
	Version 4.4 will fix this other (debug cycle) one.
]

cheers peter
-------
Date: Mon, 24 Feb 1992 10:10:36 -0500 (EST)
From: Barbara Beeton <BNB@MATH.AMS.COM>
To: PEB%DM0MPI11.bitnet@CUNYVM.CUNY.EDU
Subject: Re:  tangle.web 4.2

peter,
i've just checked at labrea.
there's no new version of tangle in /alpha so it seems that either
(1) knuth thought that there were no changes, or
(2) he forgot to install it, or
(3) the notes he accidentally sent from sweden by sea mail contained
    some more things to look at and he decided to wait.
i'll follow it up.  thanks.
i still haven't finished transcribing knuth's last set of comments,
that i received before going to england for the uktexug and tug board
meetings.  i may find something there.  maybe today ...
						-- bb
-------
Date: Mon, 24 Feb 92 16:12:49 GMT
From: Peter Breitenlohner <PEB%DM0MPI11.bitnet@CUNYVM.CUNY.EDU>
To: Barbara Beeton <BNB@MATH.AMS.COM>
Subject: Re:  tangle.web 4.2

OK thanks,
the point is that the 'extra "}" bug' is just a minor nuisence
in weave but can lead to a rather mysterious nonsense in tangle's output.
pb

************************************************************************

>>> Reply from Don

Date: 27 Feb 1993 23:48:06 -0800
Subject: note from Don

Many thanks, Barbara, for the notes you sent.

As usual, Phyllis made hardcopy for me, and I scribbled comments on
that, and wrote appropriate checks when monetary rewards were due.
The result will be wending its way to you via snail mail.

TeX version 3.1415 is done and should be available soon by anonymous ftp
from the semi-secret "alpha" [not pub] directory at labrea. A system
guru will probably install it sometime this weekend; I don't have
permission to do that. Look for file ~ftp/alpha/tex3.1415.tar.Z
at labrea.stanford.edu. Uncompressing and untarring will yield
only the crucial files that have changed: tex.web, tripin.log,
trip.log, trip.typ; also new versions of errata.tex and tex82.bug.
I think it's wise to wait awhile before releasing it officially ---
I will be updating METAFONT, some day, if that Sun file name stuff ever
is acted on --- although people are welcome to try it out. Just
a few changes: one which makes it more efficient to have everything
in a nonzero \language, another which affects kerns inserted at
the boundary characters using the smart-ligature mechanism.
(Previously such kerns were not treated consistently or correctly, so
people must not have been using them. Now they act like kerns on
accents, i.e., they do not disappear into line breaks.)

I plan to look at TeX again about 15 months from now. Thanks again for
your most helpful accumulation of pretty-much-noise-free comments.

************************************************************************

>>> Metafont/MFBook

Date: 21 Dec 1992 01:03:42 +0000 (GMT)
From: Chris Thompson <CET1@phx.cam.ac.uk>
To: Barbara Beeton <BNB@MATH.AMS.ORG>
Cc: Robert Hunt <REH10@phx.cam.ac.uk>
Subject: plain.mf bug from REH, etc.

Dear Barbara,

I should have known that Robert Hunt had been quiet for too long...
He has sent me the follo
wing:

> I have found a bug in Plain METAFONT; line 371 of the format file (in the
> definition of cutoff) should read
>   (cut_ scaled (1+max(-pen_lft,pen_rt,pen_top,-pen_bot))
> instead of
>   (cut_ scaled (1+max(pen_lft,pen_rt,pen_top,pen_bot))
>
> The METAFONTbook would also need correcting on pages 151 and 272.

[ dek --							$ 2.56
]

I think he is right that the current code is wrong, but his fix is
insufficiently drastic. The absolute values of all four pen_?
quantities needs to be taken, as they can be of any sign (although
the ones that Robert is assuming are no doubt the most likely).
One for Don's list.

Chris Thompson
-------
Date: 21 Dec 1992 21:25:37 +0000 (GMT)
From: Chris Thompson <CET1@phx.cam.ac.uk>
Subject: More on Robert's plain.mf bug

Dear Barbara,

... Robert Hunt has commented on my remarks:

> Interestingly enough, my suggested alteration
>    (cut_ scaled (1+max(-pen_lft,pen_rt,pen_top,-pen_bot))
> _is_ sufficient, and there is no need for
>    (cut_ scaled (1+max(abs pen_lft,abs pen_rt,abs pen_top,abs pen_bot)).
> This is because (as far as I am aware) the two inequalities pen_lft \le pen_rt
> and pen_bot \le pen_top hold. You'll soon see why my solution is good enough
> if you try coming up with an example where it fails!

and he is quite right---his fix is sufficient.

Chris Thompson

[ dek --
  there is another bug in cutdraw too, re the spurts of ink discussed
  on page 112.
  Both of these bugs are corrected in base_version 2.71
]

<<< end items send 23 Dec 1982

************************************************************************

>>> items sent  8 Mar 1993

Date: Mon, 13 Apr 92 12:26:16 GMT
From: Peter Breitenlohner <PEB%DM0MPI11.BITNET@vm.gmd.de>
To: Barbara Beeton <bnb@MATH.AMS.COM>
Subject: message for Knuth and a question

barbara,
Right know I am working on a modified TeX-XeT change file,
inspired by that by Knuth and MacKay published in TUGboat
but different in two essential points:
1. the text direction primitives are treated differently
   in order not to disturbe TeX's linebreaking algorithms for
   pure left-to-right text  (that is to say the new TeX-XeT
   passes the TRIP test in a much better way than the old one)
2. right-to-left text is reversed explicitely and writen to
   a normal DVI (not DVI-IVD) file.
All that is still in progress, but will be finished soon.
Can you propose a good way to make the result widely available
and known?

In doing all that I stumbled on some dubious code in tex.web.
Can you please forward the following (or the whole message)
to Knuth.

Thanks   Peter
%--------------------------------------------------------

Misleading code (or a real bug?) in tex.web V 3.141

In the hlist/vlist_out routines leader boxes are shifted
by their shift_amount. As far as I can see this shift_amount
is always zero and that code should be removed.
[dek --   ^^^^ yes, since 28 Mar 1983!
]

Even worse if there were a possibility to have leader boxes with
non-vanishing shift_amount. Then there would be a real bug since
the value of cur_v/cur_h is not reset to base_line/left_edge after
the leader boxes have been shipped out.

Here is what I think ought to be changed:

% All line numbers refer to TEX.WEB 3.141 as of March 16, 1992.

@x [32] m.628 l.12462 - remove redundant (and misleading) code
begin cur_v:=base_line+shift_amount(leader_box); synch_v; save_v:=dvi_v;@/
@y
begin synch_v; save_v:=dvi_v;@/
@z
[ dek --						$2.56
]
%---------------------------------------
@x [32] m.637 l.12605 - remove redundant (and misleading) code
begin cur_h:=left_edge+shift_amount(leader_box); synch_h; save_h:=dvi_h;@/
@y
begin synch_h; save_h:=dvi_h;@/
@z
%---------------------------------------
[ dek --
	In TeX change 668 (`Errors of TeX'] I decided that these shift
	amounts be zero, but I left the redundant code in case of future
	extensions.*  Now I see your point about the potential "real bug"
	if somebody were to actually _use_ the feature.  So I prefer to
	_leave_ these lines of code but to set
			cur_v:= base_line
			cur_h:=left_edge
	at close of \S628 and \S637

	* not in TeX itself but in private versions, as in \S1340
]

Peter Breitenlohner

************************************************************************

>>> items sent 11 Jun 1993

Date: 30 Apr 1993 22:32:17 -0300 (BST)
From: Chris Thompson <CET1@phx.cam.ac.uk>
Subject: Re: [alpha version, tex 3.1415]

Dear Barbara,

Here is a probably forlorn attempt to get a report in before your
30 April deadline:

 . No bugs found. It passed the usual paranoia tests. I have been
   using it myself (not very intensively) for routine (La)TeXing.
   I have had no adverse reports back from the 2-3 users I tried
   to subcontract the testing to (George Russell, Robert Hunt).

 . I have done a series of tests in respect of change #405 (Rainer's
   \setlanguage and associated problems): I felt I really ought to as
   Don has adopted the scheme I thought up in a particularly inspired
   moment last July (keeping the initial language/hyphenmin info for
   a paragraph in the pg_field)! It really does seem to work...

 . But a minor quibble: \showlists output now leaves no space between
   "language" and "hyphenmin" and the subsequent numbers when displaying
   this data. It used to show only the latter, but left a single space,
   which looked better.

[ dek --
  hmm, there's no accounting for taste
]

 . I *haven't* tested changes #404/#407, to do with boundary character
   logic, in any serious way. (I am rather hoping Brian has been doing
   some tests with his Greek fonts...)

If you want to contact me while while you are in this country, my work
telephone number is 0223 (Cambridge) - 334715.

Chris Thompson


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Date: 02 Apr 1993 14:39:21 +0200
From: Bernd Raichle <Raichle@informatik.uni-stuttgart.de>
Subject: Small Bug in TeXbook: \downbracefill+\upbracefill

TeXbook, Appendix B. Basic Control Sequences (page 357) states that

  The |\upbracefill| and |\downbracefill| macros have restricted
  usage: they must appear {\sl all by themselves\/} in an hbox or an
  alignment entry, except for horizontal spacing.

otherwise the \vrule "makes a heavy black band, which is too horrible
to demonstrate here" (TeXbook, page 331, answer of exercise 21.6, page
225).

In the following example \downbracefill and \upbracefill "appear all
by themselves in [..] an aligment entry":

\halign{#&&\hfil#\hfil\cr
       &\kern 5cm    &\kern 5cm\cr 
       &\upbracefill &\downbracefill\cr 
\strut &\upbracefill &\downbracefill\crcr}

The two \..bracefill in the third line of the \halign with the \strut
in column one produce the mentioned "heavy black band".


To correct the TeXbook, either

1) replace "alignment entry" to "complete alignment line" or something
   similar

   or

2) change the definition of \downbracefill and \upbracefill,
   specifying the height and the depth of the \vrule, e.g.

   \def\upbracefill{$\setbox\z@\hbox{$\bracelu$}\m@th
     \bracelu\leaders\vrule height\ht\z@ depth\dp\z@ \hfill\bracerd
     \braceld\leaders\vrule height\ht\z@ depth\dp\z@ \hfill\braceru$}
[ dek --           [delete \dp, on two lines] ^^^
                     page E89: depth _is_ _zero_ ^^^       $2.56
]

   and correct the statement about the restricted usage.


I prefer change 2, because it allows the use of \..bracefill in normal
text without a \hbox.

[ dek --
  agreed -- see plain fmtversion 3.1415
]

Yours,
  -bernd
__________________________________________________________________________
Bernd Raichle, ISR, Universit"at Stuttgart        | "Le langage est source
home:  Stettener Str. 73, D-W-7300 Esslingen, FRG |  de malentendus"
email: raichle@informatik.uni-stuttgart.de        |  (A. de Saint-Exupery)
 -------
Date: 05 Apr 1993 09:17:17 +0200
From: Bernd Raichle <Raichle@informatik.uni-stuttgart.de>
Subject: Re: Small Bug in TeXbook: \downbracefill+\upbracefill

on 04 Apr 1993 13:42:57 -0400 (EDT), bbeeton <BNB@MATH.AMS.ORG> said:
you> however, he has already completed his annual examination and
you> updated of tex and the texbook, and plans to look next at tex
you> "about 15 months from now" (as of feb 27). (i will forward his
you> comments on the bug reports and updates as soon as the "alpha"
you> version of tex 3.1415 has been vetted and pronounced sound by
you> the testers.)  so you should certainly do what is necessary
you> in the meantime to avoid this problem, if you encounter it
you> again.

This is ok for me.

Btw, I'll checked the alpha 3.1415 version of TeX on labrea and IMHO
there are two missing changes w.r.t. the change of \lefthyphenmin and
\righthyphenmin:
The fields |lhm_field| and |rhm_field| in |list_state_record| are
[ dek --
  ? they're gone ...
  change 405 in tex82.bug says to undo change 373 ...
  errata.tex correction to page B89 dated 27 Feb 93 removes them ...
  so I guess labrea is not up to date
]
unnecessary, because 3.1415 uses the |pg_field| for this purpose.  The
same applies for the definitions of the WEB macros |lhmin| and |rhmin|
in the next section.  (tex.web 3.1415 alpha, \S 212 & 213)


you> do you think this is a problem that might be encountered by
you> others?  it does remind me of a warning published in tugboat
you> a while ago (9 #2, p.183) about the depth of a rule that was
you> incompletely specified, and took on the depth of an element
you> in another cell of an \halign.  in that piece, one recommended
you> solution was to use \leaders -- but since the \*bracefill
you> macros already use \leaders, it looks like that isn't a valid
you> solution.

The TeXbook contains this warning and an explanation of this
behaviour.  (The behaviour of the \..bracefill macros with their
current definition are correct.) But the restriction statement in
appendix B, page 357 is not complete (as I have shown with the example
in my bug report). Additionally the answer of exercise 21.6 (page 331)
says:

  [..] This usually makes a heavy black band, which is too horrible to
  demonstrate here. However, it does work in the ^|\downbracefill|
                             ^^^^^^^^^^^^
[ dek --                                                      $2.56
]
  macro of Appendix~B [..]


The problem with this (mis)behaviour of \..bracefill: LaTeX's
tabular/array environments puts automatically a \strut in column one
of each alignment line making sure that the baseline distances are
equal.  Thus \..bracefill, which may be useful in a LaTeX `array', can
not be used without modifications.


you> i'll have to look over that again, and perhaps a
you> new warning should be published.  if so, i'll give you credit
you> for the report; would you be willing to review such a piece
you> before publication?

Yes.

Sincerely,
	-bernd


########################################################################

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%  Character code reference
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%                       Upper case letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ
%                       Lower case letters: abcdefghijklmnopqrstuvwxyz
%                                   Digits: 0123456789
% Square, curly, angle braces, parentheses: [] {} <> ()
%           Backslash, slash, vertical bar: \ / |
%                              Punctuation: . ? ! , : ;
%          Underscore, hyphen, equals sign: _ - =
%                Quotes--right left double: ' ` "
%"at", "number" "dollar", "percent", "and": @ # $ % &
%           "hat", "star", "plus", "tilde": ^ * + ~
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[ end of message 042 ]