TeX, LaTeX and Friends

1:40 AM

@Anthony Hello.

Hello.

General query to the (largely absent) world:
Normally, I think of \input{file} as equivalent to putting the contents of file in place of \input{file} i.e. it makes no difference whether the code is in another file, inputted, or whether it is in the main file. However, if expl3 syntax is active, it seems that it does make a difference: \file_input:n {file} is not equivalent to including the contents of file in its place. In particular, the latter ignores spaces (as expected), whereas the former does not (as not expected). This is quite handy for me, but I'm not sure why it works or what is g…

@XiaodongQi Hello.

@cfr \file_input:n preserves the \ExplSyntaxOn

@cfr Are you a developer for TikZ package?

I am just curious when you made a comment under my question on TeX.SE.

Not for me. That is, I don't understand...
\documentclass{article}
\begin{filecontents}{\jobname ABC.tex}
ABC and XYZ
\end{filecontents}

\usepackage{expl3,xparse,etoolbox}

\ExplSyntaxOn
\NewDocumentCommand \myin { m }
{
\file_input:n { #1 }

XYZ ABC
}
\AtBeginDocument{
\myin{\jobname ABC}

XYZ ABC
}
\ExplSyntaxOff

\begin{document}

123

\end{document}

@XiaodongQi No!

@XiaodongQi Why would that comment make you think I might be a developer?

1:54 AM

@cfr Seems to me you wanted to dig into that bug of TikZ. Anyway, I want to but don't know how to report bugs to TikZ team.

@cfr well, if you move \ExplSyntaxOff after \begin{document}, the spaces disappear. \file_input:n does not do anything with the catcodes, so if you're inside ExplSyntax, spaces disappear, and they do not otherwise.

@yo' I sort of understand why. I guess the \myin is not expanded until after the syntax is switched off, whereas the XYZ ABC is expanded prior to that. So you get spaces preserved in the file input but not in the rest. Still, it is counterintuitive to me... because I don't understand this well at all.

@XiaodongQi Look in the manual, find the project page for TiKZ, open web page, proceed to report? It is a sourceforge project, so sure to have a bug tracker.

@cfr "whereas the XYZ ABC is expanded prior to that" -- this part is wrong. It gets expanded at \begin{document}, but it preserves its catcodes from wherever it was written. It's written inside ExplSyntax, where spaces are ignored (by setting their catcode to the ignore value)

@yo' But then the input stuff is treated differently because that uses catcodes at the point it gets expanded rather than the point at which it is written.

@cfr well, it gets the catcodes at the moment where it's scanned. And yes, it is different.

Actually, this is something that beamer uses for fragile frames: it writes them into a file and re-reads them again

2:03 AM

@yo' Interesting. It also is a way of dealing with TiKZ stuff in a class file which switches expl3 syntax on...

But it is still counter-intuitive to me, because I don't understand the underlying TeX stuff well enough...

@cfr well, IMHO the proper solution to this problem is to create a .sty file that contains these things, and just \RequirePackage it.

@XiaodongQi You should also use the bug tracker to check it is not already reported.

@cfr Yes, it is on sourceforge. I am sending the ticket. Thanks.

@cfr I only found this report after some search effort: sourceforge.net/p/pgf/bugs/331 Seems it is still open.

@yo' I don't see why. I need to input the TiKZ stuff (1) as part of certain document commands; and (2) \AtBeginDocument to set up the contents of certain boxes which are used in document commands. If I push all of that to a separate package, I'll still have all of the inputs but now I'll have to use TeX or 2e boxes in the class rather than expl3 boxes. That seems to introduce unnecessary complications.

@cfr you should be able to do \def\myboxcontents{\fill[red] (0,0) rectangle (1,2);} and then \cs_new:Nn \cfr_box_one: {\begin{tikzpicture}\myboxcontents...}

ah well, you can do that even inside the class of course!

... my expl3 stuff ...

\ExplSyntaxOff

\newcommand\mybox { tikz code here }

\ExplSyntaxOn

.... more of my expl3 stuff ......

2:17 AM

@yo' But what's the gain? I try to keep TiKZ code in separate files anyway, so that I don't have picture code cluttering up either class code or document source. (Can compile the pictures standalone etc.) And I don't want to put the box in the picture. I want the picture in the box. And I can't do any of this until after the preamble, to be safe because the contents of the pictures uses colours which may be redefined in the preamble.

@XiaodongQi Seems so. If you can provide more information or a patch, it might get dealt with quicker. No guarantees of course.

@cfr well, I don't see your issue with ExplSyntax then, probably because it's 03:18 and I try to do some maths, too :)

@yo' I just wanted to check the behaviour was expected, because I wasn't sure why it worked and I didn't want to rely on something which might be due to my doing something idiotic at 02:00 or so ;). Sorry, I probably wasn't very clear.

[That's why I said that it was 'handy for me'. Very handy.]

@cfr well, don't worry. The thing to remember: \file_input does nothing with the catcodes. So it's better to set them properly inside the file, or inside the loader.

@cfr I am no expert in TikZ, but I think it is a good package to work with. Some of us here are thinking of re-implementing the Qcircuit package in TikZ, which was originally done in xyz-pic. I don't know if you have any suggestions? Here is the discussion post on GitHub.

@everyone Can I raise your attention on this question on how to draw ellipse on the surface of a sphere? The example code of drawing a sphere does not even work on the new version of TikZ, but I want to finish it ASAP... Thank you.

2:40 AM

@yo' Hmm... Yes. I think it is OK because it is all being used after \begin{document}. Thanks for explaining. (I asked because I was so sure that \input should not have that effect, so I'm kind of glad that I was not entirely mistaken about that, at any rate.)

@XiaodongQi I've never worked on a TiKZ package and have never used Qcircuit. Or, for that matter, any TiKZ package involved with doing anything similar. So I'm pretty much unqualified on every possible count. Good luck with it!

@cfr Good man. Thank you anyway.

@XiaodongQi Try breaking it down and asking questions about the specific things you are having trouble with. Right now, you have a whole bunch of different tasks involved in the question. For example, try starting with a question about just the first problem you've come across. Leave out all the other stuff. (Link this question for background information, but make sure your question stands on its own.) Make the code as simple as you can and focus the question on a single thing you need to do.

@cfr Thanks. I would try to make the sphere work and then back for further questions.