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Re: A few observations regarding tbl

From: Oliver Corff
Subject: Re: A few observations regarding tbl
Date: Fri, 18 Jun 2021 18:31:08 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

Hi Kurt,

U+2423 is indeed the modern representation of the character OPEN BOX. In
Donald Knuth's metafonts, this symbol is stored, appropriately, in
position 32 (or 0x20) because TeX as such has no awareness whatsoever of
"a blank space". It knows horizontal distances, but doesn't treat 0x20
as a _character_, in true typesetting tradition, and treating 0x20 as a
character implies something visible in that particular position.

So going for U+2423 should be the most appropriate way, and I can best
think of a replacement character for visible spaces in my code
demonstration which is then replaced in the output by U+2423.

Perhaps I am not going to mimick everything in Lesk's text, as I also
want to focus on how a user can construct a large table without too much
chagrin and headache.


On 6/18/21 6:07 PM, T. Kurt Bond wrote:
I would have thought .tr would be of use here, but I can't get it to
translate a space to something else, probably due to how its arguments are
parsed.  (It doesn't strip off a leading double quote, of course.)  Cursory
experiments with .char didn't seem to work either.

So I tried manually replacing spaces with the Unicode character U+2423
(OPEN BOX): ␣ (if that shows up in your mail client).  I remember seeing
spaces represented with a similar glyph in various sources.  That character
is not in the Courier font, but is in DejuVuSansMono, so I installed the
DejaVu fonts (thanks to Peter Schaffter's
<> script) and that
worked ok.  It should be possible to run the tbl source of your tables
through a script that substitutes the OPEN BOX character for all spaces.

I was going to suggest that the script change tabs into the Unicode
Character CIRCLED LATIN CAPITAL LETTER T, but that's not in
DejaVuSansMono.  (Lesk used a T overstruck on a circle.)

And then I got to thinking: If you want something in Courier (so as to not
have to install a font), you might try substituting Unicode Character WHITE
CIRCLE for spaces and WHITE SQUARE for tabs.  That is not mnemonic as the
circled T and OPEN BOX, alas.  Or you could use the groff characters \[ci]
and \[sq]; that would probably be easier than messing with Unicode
characters.  Or you could try overstriking S and T on \[ci], although when
I try that the result has the bottom of the S and T over the bottom of the

Anyway, here's the test document I used:

This is a paragraph.
.ft DejaVuSansMonoR
.ft C
This○is□a◊sentence with Unicode WHITE CIRCLE, and WHITE SQUARE.
This\[ci]is\[sq]a\[ci]sentence with groff characters \\[ci], and \\[sq].
Using "\fC.char \\[overstrucks] \\o'\\[ci]\\s[-4]S\\s0'\fP", etc.
.char \[overstrucks] \o'\[ci]\s[-4]S\s0'
.char \[overstruckt] \o'\[ci]\s[-4]T\s0'
.ft C
This\[overstrucks]is\[overstruckt]a\[overstrucks]sentence with overstruck
characters and .char.
This is a paragraph.

and here is what the output looks like:
[image: image.png]
Does anybody have other ideas?

On Fri, Jun 18, 2021 at 9:16 AM Oliver Corff <> wrote:


I thought over the subject and I decided to write a new introduction to
tbl, akin to Lesk's introduction, but under FLOSS license and with a
focus on the gnu extensions.

For this purpose, I have one obviously uninformed and stupid question.
How do I show code examples in groff (I think I'll opt for the ms macro
set) with the whitespace character 0x20 marked, akin to the \verb*|...|
command in LaTeX? \verb|...| produces the included text in tt courier
(or another fixed-pitch font suitable for displaying code) with spaces
shown as blank, whereas \verb*|...| inserts a special symbol for every
0x20 character.

Does the ms macro package feature an environment for displaying source
code, or do I mimick that with font and margin settings?

Since my introduction will demonstrate things like nospaces, tab
settings etc., it would be nice to show the spaces in the source code.

Thanks a lot, and I am happy to take the beating if this question
demonstrates that I was the last one to ask.


On 17/06/2021 18:46, G. Branden Robinson wrote:
Hi, Oliver!

At 2021-06-15T12:39:02+0200, Oliver Corff wrote:
my huge text project which involved typesetting approx. 1,300 tables,
tiny, small, large and huge, demonstrated that tbl is a remarkably
powerful and reliable tool for this work, and I can say with
confidence that the question which type of table software to use
(LaTeX? (x)html?  others?) was best answered by tbl which helped me
recreate tables with a fidelity so close to the printed sources that
the uninitiated reader could not tell an image of the page from the
typeset reproduction.
That's excellent news!

What is the copyright licensing status of these 1,300 tables?  Is there
a chance we could get a small, potentially simplified subset of them
under a FLOSS license so that we could use them to illustrate GNU tbl's
feature set?  An excellent property of Lesk's tbl paper was the suite of
examples, but we don't have that document in our distribution and the
few examples in our tbl(1) man page compare poorly.

Speaking of the feature set, how much of GNU tbl's feature set do you
figure you ended up exercising by the end of this project?  Was there
anything that you expected to use but ended up not needing?

I came across a few very minor discrepancies between expected and
actual behaviour, though.

1) For the global option "tab(x)", the man page says:

      tab(x) Use the character x instead of a tab to separate items in a
line of input data.

This works as long as x is a 7-bit ascii character, it does not work
with utf-8 characters. E.g.: "tab(|)" (with the pipe symbol) works,
"tab(¦)" does not work and yields the message: "argument to `tab'
option must be a single character".

I suggest either specifying "7-bit ascii character" in the manpage
and/or make the tbl parser utf8-aware.
Hmmm, yes--since tbl parses the table for itself, *roff special
character escapes will not serve as a workaround.  And UTF-8 support
would be a significant undertaking.

I've filed this as <>.

2) The global option "nospaces", according to the manpage, is
described as:

      Ignore leading and trailing spaces in data items (GNU tbl only).

The following point may be a question of correct interpretation of
this statement. Does the underbar "_" qualify as a data item in this
terminology? I positively think so, because the manpage states

      If  a  data  line  consists of only ‘_’ or ‘=’, a single or double
line, respectively, is drawn across the table at that point;

If my data line consists of a single '_', that line is drawn. However,
if that '_' is followed by spurious whitespace, then only the '_'
appears in the first cell, and no line is drawn, or a line spanning
the first cell only is drawn. From a logical point of view, this is
clear, as the statement says "consists of only ...", but the nospaces
option does not seem to work here as expected.
Doug's follow-up to this point seems reasonable.  For me, it reinforces
the principle I espouse that diligent management of one's lexicon is one
of the most important things you can do in a software project.

When revising the tbl(1) man page in the future, I will attend closely
to the uses of the terms "data line" and "data item", and try to make
sure they're correct and consistent.

I once got partway through a rewrite of tbl(1) (the page) once, with
much terminological alteration around "global option", "column
specifier", and "column modifier".  I disfavor the term "global option",
because "global" options don't persist beyond a .TS/.TE table region,
not even in the same document.  I don't think novice users' concept of
something "global" stops anywhere short of the entire file they're

I ran out of steam on that project because there was just too damn much
I wanted to fix about the man page.  Not having a separate document (as
AT&T tbl had) to point the user to for practical examples was a major
problem, hence my request above.  Coming up with a good suite of
examples is itself a significant undertaking, and while I found the
examples contributed by Bernd to be contrived and meager, I couldn't
honestly say that they weren't better than nothing.

In my ideal world, tbl(1) would describe the syntax of the command and
its input (or the latter could be migrated to a tbl(7) page--I suspect
that would win Ingo's support and it wouldn't bother me at all), and
we'd have a separate document chock full of source alongside
rendered examples for users to emulate, experiment with, and build
their expertise with.


Dr. Oliver Corff
-- China Consultant --
Wittelsbacherstr. 5A
D-10707 Berlin
Tel.: +49-30-8572726-0
Fax : +49-30-8572726-2

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