TeX, LaTeX and Friends

7:51 AM

@PhelypeOleinik no, you're right, my memory was tricking me again :( Yesterday evening was no good day for me and my TeX skills :)

Paulo Cereda

8:39 AM

quack

Skillmon

8:57 AM

\int_new:N \l__bitset_tmpa_int
\prg_new_protected_conditional:Npnn \__bitset_test_int:n #1 { TF }
  {
    \tex_afterassignment:D \__bitset_test_int:w
    \l__bitset_tmpa_int = 0 \tl_trim_spaces_apply:nN {#1} \tl_to_str:n
    \__bitset_test_int_end:
    \use_i:nnn \if_false:
    \__bitset_test_int_end:
    \if_int_compare:w \c_zero_int < \l__bitset_tmpa_int
      \prg_return_true:
    \else:
      \prg_return_false:
    \fi:
  }
\cs_new_eq:NN \__bitset_test_int_end: \exp_stop_f:
\cs_new_protected:Npn \__bitset_test_int:w #1 \__bitset_test_int_end: {}

@PhelypeOleinik ^^^ a slightly faster variant of your test...

(takes roughly 40% of the time of your test to test 123 and 12a)

Ulrike Fischer

@Skillmon I have lots of tea and cookies here (but no popcorn) ;-)

Paulo Cereda

@UlrikeFischer ooh

Jairo A. del Rio

@PauloCereda Eendenvlees

Skillmon

@UlrikeFischer good idea, I'll go and make me a coffee :)

daleif

@campa just wondering, why did you delete your answer to that flashcard vs align question yesterday?

Joseph Wright

9:12 AM

@Skillmon Will commit shortly

Skillmon

@JosephWright also, maybe the name should be changed to test_number, as it doesn't really test for an int in the meaning of expl3, as that would also be a valid \numexpr.

Ulrike Fischer

@Skillmon or perhaps test_digits? @JosephWright

Skillmon

@UlrikeFischer it's internal, so I guess it's not too bad if the name doesn't fit perfectly, but test_int sounds wrong... So, yes, that would be fine, too :)

campa

9:28 AM

@daleif I wasn't entirely happy with it. The overfull \hbox kept showing up and I had no time to work out where the issue is. I'll look into it later.

@daleif And I wasn't completely sure that I had picked out the best \hbox\bgroup\vbox\bgroup orgy ;-)

daleif

9:45 AM

@campa that seems fair.

Faheem Mitha

In the following file

\documentclass[12pt]{scrlttr2}
\begin{document}
\begin{letter}{}
  \opening{To whom it may concern}
\closing{Yours sincerely,}
\end{letter}
\end{document}

I get the error

 LaTeX Error: There's no line here to end.

Why does this error happen, exactly? It goes if I put anything inside the second arg of \begin{letter}.

campa

@FaheemMitha Use \begin{letter}{\strut}

Faheem Mitha

@campa Actually, \phantom{} works. And doesn't seem to add anything, as far as I can see.

But my question is, what does this error mean?

campa

@FaheemMitha Uh, I had looked into it but I honestly forgot. You get that error when you have `\` in vertical mode. Was the test for emptiness of the recipient not entirely safe? Could be, but I might be wrong.

Faheem Mitha

@campa Ok. I just thought it would be helpful to know why it happens.

campa

9:55 AM

I meant \\ in vertical mode

Faheem Mitha

Helpful and instructive. Should ask a question?

@campa Where does `\\` appear?

campa

@FaheemMitha Newlines are used when the recipient's address is set.

Faheem Mitha

@campa I see.

This is probably not the best place to ask for an analysis. Should I ask a question? It might be a dupe.

campa

@FaheemMitha There are a couple of related questions but as far as I can see no one investigates the cause. It might be worth a question, though I think it's more an "academic" issue.

Faheem Mitha

@campa An "academic" issue?

BTW, the same error appears with the vanilla letter class.

campa

10:01 AM

@FaheemMitha Well, how often does it happen that you write a letter without an addressee? :-) That's what I meant. As TeX question it's legitimate and interesting.

Faheem Mitha

@campa Actually, I did have one. That's why I'm asking the question.

Not all letters need an address. What does \strut do?

@campa So you think it's a reasonable question to ask?

Paulo Cereda

@JairoA.delRio oh no

campa

@FaheemMitha \strut introduces a \strutbox, basically a box with zero width but height and depth of a parenthesis.

Faheem Mitha

@campa Ok.

I'll go ahead and ask a question. It's a simple enough question.

campa

@FaheemMitha There are some related question but I haven't found anything describing exactly why it goes wrong. I think it's worth a question.

Faheem Mitha

10:07 AM

@campa Ok. Thank you.

Skillmon

3

Faheem Mitha

@Skillmon Congratulations.

Jairo A. del Rio

@PauloCereda Hans told me ducks were once popular in Dutch food. A really weird remark considering I was asking for clarification concerning MetaPost :D

Paulo Cereda

@JairoA.delRio ducks are an interesting subject. :)

3

Jairo A. del Rio

@PauloCereda As TeX (and Lua imho) are :)

Paulo Cereda

10:14 AM

@JairoA.delRio quack :)

Faheem Mitha

@campa Asked question.

campa

@FaheemMitha I've managed to restrict the issue: the macro \opening executes among other things \@addrfield, and this types the addressee followed by a \\, which will cause the error if the addressee is empty. But there are still some details I'm disentangling...

Faheem Mitha

@campa Are you planning to write an answer?

I was thinking of asking the author of KOMA-script to allow blank addresses.

Not sure it's worth the trouble, though.

campa

@FaheemMitha I might, but there is this nasty thing called "work" which also requires some time :-) I won't be able to write one until the late afternoon. Maybe someone else will answer first

Paulo Cereda

@campa This person being @DavidCarlisle :)

campa

10:29 AM

@PauloCereda I was counting on that ;-)

Paulo Cereda

@campa he needs teh rep points. :)

Faheem Mitha

@campa Ok.

I didn't know you could ask TeX to produce an error stack. That's like a traceback?

Paulo Cereda

@FaheemMitha no, it shows the surrounding lines in which the error was found

Faheem Mitha

@PauloCereda Ok. The surrounding lines in the TeX source code?

Paulo Cereda

@FaheemMitha yes

Faheem Mitha

10:35 AM

@PauloCereda I see. Thank you for explaining.

Paulo Cereda

@FaheemMitha NP, David cheats by reading code. :)

Faheem Mitha

I'm not 100% on his explanation. He flagged toname. But isn't toaddress the culprit?

David Carlisle

@PauloCereda didn't see this thread first:-)

@FaheemMitha I didn't flag anything I just showed you what tex reported. The name is probably the first line of the address.

@PauloCereda not really it is more like a stack trace

@PauloCereda no

@PauloCereda no I didn't look at the code just at the stack trace (context lines) of the error. \errorcontextlines controls how many levels of expansion to unwind in the error message not how many source lines are shown.

Faheem Mitha

@DavidCarlisle Probably. But what about the other \\ later on?

David Carlisle

@FaheemMitha Always stop at the first error. There is no "later on".

Paulo Cereda

10:49 AM

@DavidCarlisle vvv

> TeX will show only the top and bottom pairs of context lines together with up to \errorcontextlines additional two-line items. (If anything has thereby been omitted, you'll also see '...'.)

Faheem Mitha

@DavidCarlisle Oh.

Paulo Cereda

@DavidCarlisle sorry, this does not sound like stacktrace

David Carlisle

@PauloCereda well looking at it you see all the macros that were expanded to get from the source line to the eventual error, so literally you see the current input stack of macro replacement texts that are not completed. You do not see more lines of the original source

Paulo Cereda

@DavidCarlisle okay, so blame the TeXbook text.

@FaheemMitha sorry, I stand corrected. ^^

Faheem Mitha

@PauloCereda No problem.

David Carlisle

10:58 AM

Mar 26 '12 at 19:37, by David Carlisle

@Canageek moral of the story: never read the documentation, bad things happen

Paulo Cereda

@DavidCarlisle ooh

Faheem Mitha

@PauloCereda Is \errorcontextlines mentioned in the TeXBook? What does it say?

David Carlisle

@FaheemMitha as @PauloCereda says, it says this:

\ddanger If you use \TeX\ format packages designed by others, your
error messages may involve many inscrutable two-line levels of macro
context. By setting ^|\errorcontextlines||=0| at the beginning of your file,
you can reduce the amount of information that is reported;
\TeX\ will show only the top and bottom pairs of context lines
together with up to |\errorcontextlines| additional two-line items. \ (If
anything has thereby been omitted, you'll also see `|...|'.) \ Chances
are good that you can spot the source of an error even when most of a

Paulo Cereda

@DavidCarlisle \oops

@DavidCarlisle thank you <3

David Carlisle

latex sets it to -1

Faheem Mitha

11:04 AM

@DavidCarlisle What does -1 do?

David Carlisle

@FaheemMitha it shows as little internal detail as possible

Faheem Mitha

@DavidCarlisle Oh, so not even the top and bottom pairs of context lines?

David Carlisle

@FaheemMitha you always get the error message and the original source line but not the intermediate internal expansions. I forget now when it differs from 0 I think it is the handling of showing argument values, it is in any case the smallest error messages possible

Faheem Mitha

@DavidCarlisle More context is generally useful. I'll keep it in mind in the future.

David Carlisle

@FaheemMitha it is simpler for you to try than ask.

By default you get

! LaTeX Error: There's no line here to end.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.5   \opening{}

? x

If you set it to 0 you get

! LaTeX Error: There's no line here to end.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

...
l.5   \opening{}

?

so one extra level of ... so not that useful.

Faheem Mitha

11:09 AM

Ok.

Paulo Cereda

@DavidCarlisle backpropagation in a nutshell?

David Carlisle

@PauloCereda we didn't want to have to admit quite what \latex@error does to format the error message (command names with so many spaces in the name tex does not log them) that is the extra ... in the errorcontextlines=0 case

Paulo Cereda

@DavidCarlisle ooh so can we blame @UlrikeFischer?

David Carlisle

@PauloCereda Alan, I think.

Paulo Cereda

@DavidCarlisle ooh Turing :)

David Carlisle

11:12 AM

@PauloCereda nope this one % \changes{v1.1a}{1994/05/16}{(ASAJ) Completely new error interface.}

Paulo Cereda

@DavidCarlisle ooh

David Carlisle

such a readable command name:

%    %<-------------------do not delete this space!------------------->%
\@err@                                                                 %
}}%

@PauloCereda the command starts \@err and ends at the %

Paulo Cereda

@DavidCarlisle ooh 65 spaces

campa

@FaheemMitha The code executed at \begin{letter} checks if the argument is empty: if it is not, it grabs everything up to the next \\ and uses that as toname, the rest is treated as toaddress. If the argument is empty then both are empty and the error occurs.

Faheem Mitha

@campa So having a non-empty toname suffices?

What's that second \\ in the traceback?

campa

12:04 PM

@FaheemMitha The box is typeset twice, hence the two errors. I've added an answer.

campa

12:31 PM

@daleif Alright, I've (more or less) got it. The overfull \hbox is an artifact of not having declared three flashcards. It's not really worth fixing it, so I removed the related comment and un-deleted my answer.

Faheem Mitha

1:00 PM

@campa Thank you. There are two errors?

campa

@FaheemMitha When you compile your code you get the error twice

Faheem Mitha

@campa Oh? I didn't notice that.

yo'

2:09 PM

3

samcarter_says_quack

2:33 PM

@yo' Maybe @DavidCarlisle could write the alltehthings package?

yo'

@samcarter_says_quack oh definitely :)

Ulrike Fischer

@samcarter_says_quack and blame me for the typo?

samcarter_says_quack

@UlrikeFischer yes (and sorry for the ping)

Joseph Wright

3:30 PM

@UlrikeFischer We are pretty sure we want \pdf_destination:nnnn without any 'content', right?

@UlrikeFischer Also, are you happy with \pdf_destination:nn having two rather different possible types of arguments?

Ulrike Fischer

3:43 PM

@JosephWright well for me in hyperref it is the right thing. And imho it is also more logical: a destination doesn't have "content".

Joseph Wright

@UlrikeFischer OK, altering the backend

Ulrike Fischer

@JosephWright I thought you needed the content there for one of the backends.

@JosephWright you mean the fit, fith, xyz etc and the scale factor?

Joseph Wright

@UlrikeFischer Not if we decide there is no content: I can construct an empty space at the backend level

@UlrikeFischer Yes

@UlrikeFischer I do wonder if we need \mode_leave_vertical:?

David Carlisle

3:59 PM

Jul 24 '17 at 15:28, by Paulo Cereda

@samcarter you are mean <3

@JosephWright on all destination whatsits?

Ulrike Fischer

@JosephWright it works without it (I tested ...) and some of the hyperref code would error if it would be suddenly added.

Joseph Wright

@UlrikeFischer Ah

@UlrikeFischer That makes life a bit more interesting, I guess: I need to think a little

Skillmon

@JosephWright strictly speaking, the \__bitset_test_digits_end: macro isn't necessary and could as well be \exp_stop_f: directly (since #1 is \detokenized, there is no possibility to reduce stability this way).

Paulo Cereda

@samcarter_says_quack twitter.com/hyxpk/status/1354459158565642261

Ulrike Fischer

@JosephWright this here is more or less the problem: it errors with the \leavevmode:

\documentclass{article}
\usepackage{hyperref}
\makeatletter
\Hy@WrapperDef\new@pdflink#1{%
  \ifhmode
    \@savsf\spacefactor
  \fi
  \Hy@SaveLastskip
  \Hy@VerboseAnchor{#1}%
  \Hy@pstringdef\Hy@pstringDest{\HyperDestNameFilter{#1}}%
  \leavevmode\Hy@DestName\Hy@pstringDest\@pdfview
  \Hy@RestoreLastskip
  \ifhmode
    \spacefactor\@savsf
  \fi
}
\makeatother
\begin{document}

aaa

\refstepcounter{section}

xxx

\end{document}

Ulrike Fischer

4:21 PM

@JosephWright well personnally I think that all this arguments (including the fitr + width +..) is of the same type and describe an instruction how to display the page. It is okay to do the fitr with a special command as it is a box, but I don't see a reason why zoom should be special.

samcarter_says_quack

4:50 PM

@PauloCereda ohh :)

David Carlisle

5:07 PM

@UlrikeFischer youd have to put it first and drop the ifhmode tests but I'm not sure always doing \leavevmode is the right thing

\documentclass{article}
\usepackage{hyperref}
\makeatletter
\Hy@WrapperDef\new@pdflink#1{%
  \leavevmode
    \@savsf\spacefactor
  \Hy@SaveLastskip
  \Hy@VerboseAnchor{#1}%
  \Hy@pstringdef\Hy@pstringDest{\HyperDestNameFilter{#1}}%
  \Hy@DestName\Hy@pstringDest\@pdfview
  \Hy@RestoreLastskip
    \spacefactor\@savsf
}
\makeatother
\begin{document}

aaa

\refstepcounter{section}

xxx

\end{document}

@UlrikeFischer ^

Ulrike Fischer

@DavidCarlisle yes, but as you said: it is not clear if one wants to leave vmode for all the various locations where the hyperref code inserts destination. Also this is not a place where @JosephWright can inject the \leavevmode. The backend would rely on hyperref behaving.

Joseph Wright

5:39 PM

@UlrikeFischer OK, then the question is are we safe with \box_move_... and even more so with \tex_kern:D

@DavidCarlisle, @UlrikeFischer I do wish we could have an interface for \kern

David Carlisle

@JosephWright probably not, do you have an example?

Skillmon

@JosephWright why don't we have an interface for it?

Ulrike Fischer

@JosephWright is it already implemented? I could run a test (but as long as it doesn't error and give a 0-size box it should be fine, it didn't work at all previously with pdftex, so nobody can complain that it changed ...)

Joseph Wright

@DavidCarlisle Not at the moment: I guess I should check how hyperref does stuff

@UlrikeFischer Yes

@Skillmon It's 'typesetting'

Skillmon

@JosephWright so is boxing up stuff.

@JosephWright also, what about packages written in expl3 that use code to typeset things? I never understood why 'typesetting' is not included in expl3.

David Carlisle

5:52 PM

@JosephWright specials in vmode are usually wrong but leavevmode isn't necessarily the best way to avoid it \vbox{<special>\hbox{...}...} might want to be \vbox{\hbox{<special>...}...} rather than \vbox{\leavevmode<special>\hbox{...}...}

Joseph Wright

@DavidCarlisle Indeed

@Skillmon Er, yes: talk to Chris ;)

@Skillmon Well, it's complicated ...

Paulo Cereda

@JosephWright oh no

Joseph Wright

@Skillmon At least in part as the typesetting end of things hasn't to-date been needed for 'kernel stuff'

David Carlisle

@JosephWright but even without typesetting we should probably have basic allocation and kern (dimen) arithmetic to match l3skip

Ulrike Fischer

@JosephWright pdflatex works fine, but xelatex errors:

! You can't use `\lower' in vertical mode.
\box_move_down:nn #1#2->\tex_lower:D
                                     \__box_dim_eval:n {#1}#2

David Carlisle

6:00 PM

hmm that isn't quite what I meant (as they are there..)

Joseph Wright

@DavidCarlisle I refer the gentleman to my previous answer

@UlrikeFischer Ah, that's what I was afraid of ... I'll think a bit more

5 mins ago, by Joseph Wright

@Skillmon Er, yes: talk to Chris ;)

Ulrike Fischer

@JosephWright can't you put it into a \hbox as I did?

Joseph Wright

@UlrikeFischer Sure, I was just aiming to avoid boxes that are not needed ... I'll think a bit

Paulo Cereda

@JosephWright oh no

Joseph Wright

@UlrikeFischer Probably: need to decide at what level it lives

@UlrikeFischer I think you are right: I'll go with that :)

@UlrikeFischer Try now :)

Ulrike Fischer

6:38 PM

@JosephWright sorry had to prepare dinner, I will check now.

Paulo Cereda

@UlrikeFischer oh no?

Ulrike Fischer

@PauloCereda Wiener Reisfleisch. No ducks involved ;-)

Paulo Cereda

@UlrikeFischer phew :)

David Carlisle

@UlrikeFischer there is always tomorrow

Joseph Wright

6:59 PM

@DavidCarlisle /quacks sadly

3

Paulo Cereda

@JosephWright oh

@DavidCarlisle oh no

David Carlisle

@JosephWright you won't feel a thing...

Ulrike Fischer

@JosephWright I get a missing number error with xelatex:

\__kernel_backend_literal:n #1->\__kernel_backend_literal:e {\exp_not:n {#1}}
#1<-pdf:dest (section.1)[@thispage/FitR @pdf_section.1_llx @pdf_200.75pt_lly @x
pos @ypos]

! Missing number, treated as zero.
<to be read again>
                   s
<argument> s
            ection.1
\__pdf_backend_destination_aux:nnnn ..._kern:D -#2
                                                  \scan_stop:

Joseph Wright

@UlrikeFischer Hmm, I must have mixed up the arguments

@UlrikeFischer Should now be fixed

Ulrike Fischer

@JosephWright no error, but the destination doesn't look right. it creates this:

[3 0 R/FitR 7 0 R 8 0 R 333.77 683.21]

the object 7 0 is fine, but 8 0 is null:

8 0 obj
null
endobj

Joseph Wright

7:05 PM

@UlrikeFischer Just dvipdfmx, right?

Ulrike Fischer

@JosephWright yes (I didn't test dvips yet, will do now)

Joseph Wright

@UlrikeFischer Fixed I think

@UlrikeFischer We will get there soon :)

Ulrike Fischer

@JosephWright latex has also the missing number error.

Joseph Wright

@UlrikeFischer Oh drat

Ulrike Fischer

@JosephWright dvips now: /D [5 0 R /FitR 133.768 683.215 333.768 883.215] all good ;-)

@JosephWright I'm not sure if everything is good. I get different values:

pdflatex /D [5 0 R /FitR 133.768 633.325 333.768 833.325]
xelatex     [3 0 R/FitR  133.77  433.33 333.77 633.33]
dvips   /D  [4 0 R /FitR 133.8   444.240021 333.72 644.28]

Why are the dvi backend by 200 down?

Ulrike Fischer

9:18 PM

@JosephWright something is wrong if a destination has a depth, then it inserts space with xelatex and latex+dvips:

\documentclass{article}
\usepackage{l3pdf}
\begin{document}
abc

\ExplSyntaxOn
x\pdf_destination:nnnn {test2}{150bp}{100bp}{200bp}
\ExplSyntaxOff

\end{document}

Joseph Wright

@UlrikeFischer Drat

user27286

10:32 PM

@barbarabeeton Thanks

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$TeX - LaTeX$ TeX, LaTeX and Friends