{tex-core} is for questions that are independent of formats and macro packages. Such questions usually relate to low-level TeX programming or the behaviour of TeX at an underlying level. Note that even Plain TeX is a format in itself; for questions about it, use {plain-tex}.

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13
votes
1answer
211 views

How to find out if a math list consists of a single character?

When accents are placed, the TeX engine gives single characters a special treatment; see the TeXbook, Rule 12 on page 443. See also this question and its accepted answer for details. Thus, ...
13
votes
4answers
638 views

File copy without expansion

What is the command for file copy? I want to copy the contents of one file into another without any command expansion. The operative system would use copy source target I tried reading the contents ...
13
votes
3answers
2k views

How to use \valign?

I just bumped into a interesting command called \valign. It seems to be the sister of \halign, but the TeXbook seems to be rather shy on explaining its use. As is the TeX by Topic. They only mention ...
12
votes
4answers
967 views

Making efficient use of \writes

I'm currently trying to compile my thesis using LaTeX and have run up against the old ! No room for a new \write . problem. After some googling it seems the only way to actually resolve this problem ...
11
votes
1answer
545 views

How to do \scantokens inside \edef without triggering “Runaway definition”

I'm trying to find a way to use the e-TeX \scantokens command inside [the equivalent of] an \edef (well, actually an \xdef, but presumably this does not make any real difference since that's just the ...
10
votes
5answers
775 views

Teach me how to use \loop…\repeat constructs, etc

The following code snippet is a part of the solution given here: \def\IncludeOutput#1{ \parskip=2mm \def\examplename{#1} \pdfximage{\Directory/\examplename.pdf}% ...
9
votes
2answers
859 views

How to avoid underfull vbox in combination with \vsplit?

In the following example I am using the command \vsplit. I can't see the reason why \vsplit produced an overfull \vbox \documentclass{article} \parindent0pt \def\exampletext{Text Text Text Text Text ...
8
votes
6answers
901 views

Function like macro?

If you have programmed in a high level programming language, you must be familiar with the concept of functions, subroutines which return a value. For example, if you write in C, you can write a ...
5
votes
3answers
224 views

Possible CSS type features?

Hi I am doing a project for my 10th grade Graphic design class and we have to make up an inspirational type thing with the emotion words Bold, in a bigger size and capitalized and I was wondering if ...
4
votes
5answers
617 views

Continuously-sizable fonts?

Why are we stuck with a finite number of font sizes in LaTeX? Modern fonts are fully vector-based and scalable - why can't LaTeX do this? Or maybe it can, and I just don't know how. Also see the ...
24
votes
3answers
842 views

How to know whether or not we need \expandafter?

The following is quoted from Peter Grill's answer on question LaTeX dynamic macro definition. The \expandafter is requried as the \newcommand needs to be dealt with after the \csname. As a ...
23
votes
2answers
503 views

Backward definition of (La)TeX commands

Again and again I see, that TeXnicians define commands and do several things with them in the reverse order, I would do this as amateur. See this example: In his answer to scrpage2: Three ...
22
votes
6answers
3k views

What is \iffalse for?

So this is something I've wondered about for a while. What use is a conditional that always evaluates to false? I guess it's a neat way to "hide code from LaTeX" but apart from that, is it ever ...
22
votes
2answers
1k views

What’s behind \over?

Typically a TeX command have arguments coming after it. But the command \over, which is used to produce fractions, can access the token before it. How exactly is it implemented and can I define a ...
16
votes
2answers
3k views

What's the difference between \tolerance and \badness ?

I'm having some difficulty understanding this sentence on page 29, Chapter 6 of Knuth's TeXbook: Run TeX again, and begin this time by saying \hsize=2in \tolerance=1600 \input story ...
15
votes
4answers
548 views

Selectively suppress generation of typeset output

Is it possible put TeX into a "mute" mode in which all typesetting is suppressed? \documentclass{article} \pagestyle{empty} \begin{document} \suppress This text will not be seen in the generated ...
15
votes
2answers
1k views

How to add a hook to a macro

LaTeX uses hooks extensively, one method employed is the command g@addto@macro. It is defined in source2e as: \long\def\g@addto@macro#1#2{% \begingroup \toks@\expandafter{#1#2}% ...
10
votes
1answer
326 views

Interwoven alignment preambles are not allowed - what exactly does this mean?

I admit that this post is purely idle curiosity. But I recently stumbled upon a little factoid saying that the TeX error "Interwoven alignment preambles are not allowed" has the following explanation ...
10
votes
5answers
1k views

Can I see a plain TeX source file please?

all the LaTeX-tutorials tell me how LaTeX is an extention simplifying the building of TeX documents. Understandably, no one uses plain TeX anymore, right? But I seem to learn better when I grasp the ...
9
votes
1answer
991 views

Origin and formation to the ERROR ‘Dimension too large’

When I tried to compile: \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \draw[very thin, red] (0,0) circle (2); \foreach \i in {0, 1, 2, ..., 46} \draw[very thin, ...
9
votes
1answer
626 views

Trapping LaTeX error/warning

Is there a way to trap an error/warning in LaTeX during compile time? I'm thinking of something similar to the VB script On Error Goto <blah>, but this time for LaTeX in something like ...
7
votes
2answers
114 views

Is there a way of defining a command \nullifyifmoved{arg} that will normally act like its argument but act like a no-op if the macro is “moved”?

I'm interested in a macro \nullifyifmoved that takes one argument arg and acts like arg in normal contexts, except it acts like a no-op wherever it is written to a file. Some background: Martin ...
7
votes
5answers
318 views

What sequence of documents should I read to know “all of” TeX and then LaTeX?

I know that there are a already number of questions on this site about good instructional (La)TeX materials for users at different levels. What I am interested in, though, is what set of documents ...
4
votes
2answers
201 views

alternative syntax of subscripts using tex

I would like to sometimes write subscripts using different syntax, instead of $u_{xx} blahblah$ write something like $u⎵xx blah blah$, or even $u⎵xx+blah blah$ where either space following the x ...
4
votes
2answers
344 views

What is the ConTeXt or plain TeX equivalent of \nolinebreak?

The command \nolinebreak[4], if placed between two characters, should prevent a line break from appearing in that location. This command does not seem to be defined in ConTeXt. Is there an equivalent ...
15
votes
3answers
3k views

What is the difference between \ifx\somecommand\undefined and \ifdefined\somecommand\else?

What is the difference between \ifx\cyrdash\undefined and \ifdefined\cyrdash\else? \cyrdash is any macro.
12
votes
1answer
250 views

Test if a number is in a comma separated range/list of numbers

Martin Scharrer posted a very elegant answer for the question "Creating a zebra effect using listings". I want to extend that code to highlight only lines given in a comma separated list. The ...
10
votes
1answer
285 views

Macro delimiter

I'd like to have a macro to split up another macro content, with field separator being a space. So: \def\mytext{foo bar} \def\secondof#1 #2{#2} \secondof\mytext What? What do you mean: "runaway ...
9
votes
4answers
564 views

How do I get the category code of a character that is the value of a control sequence?

How can I get the category code of a character that is the value of a control sequence? If I do this The catcode for A is \the\catcode`A. I get The catcode for A is 11. If I do this \let\abc=A ...
8
votes
2answers
152 views

Commands that disable everything except the counters

what I'm looking for... I'm looking for a couple a commands, \disableAllButCounters and \enableAll that would do the following: Everything between \disableAllButCounters and \enableAll would ...
7
votes
3answers
342 views

Making mathmode obey spaces

I know this is kind of blasphemic thing to ask, but is there a way to make mathmode obey spaces? Preferably in Plain with XeTeX.
6
votes
1answer
347 views

Equation tag in twoside-mode outer

At the moment I thinking about the following think. When I use the twoside mode to write a book I want to print the number of the equation outer. I can modify it manually with these two commands: ...
6
votes
2answers
300 views

Is there a way to dissect math lists?

In the course of trying to answer this question, I now realize that I need to be able to construct a math list and then check if it consists of a single character atom. What I would like to be able ...
5
votes
1answer
320 views

What is the proper way to prevent text from splitting across columns and pages?

I have some description environments which I do not wish to have split across columns or pages. Is there some command which can be placed around an item to ensure that it will never be split across ...
5
votes
1answer
188 views

How can I reverse the order of letters/tokens?

I want a simple way to have: \reverseit{abc defg \mycommand} yield \mycommand gfed cba ? (Yes, the original motivation is related to Hebrew and RTL languages, but that can sort of be solved ...
4
votes
1answer
215 views

Luatex os.execute not working

I've hooked luatex's stop_run callback so I can do some processing on the output pdf after it is generated. To process the pdf I need to call os.execute. When doing so I an error saying "All command ...
3
votes
3answers
238 views

Retain side-effects but discard command output

The following code works, although I have a feeling my \settowidth method of discarding the output is not how it should be done: \documentclass{article} \newlength{\trashlength} ...
2
votes
3answers
99 views

Conflict with packages in printing out ƒ in \begin{equation} mode

The initial thread solved the main problem, but there is now some conflict with packages that I do not understand. My tex code \documentclass{article} \usepackage{amsmath, amsfonts, amssymb, ...
2
votes
2answers
277 views

An expandable 'character scanning' command?

Please consider the following MWE, for a "character scanning" command "\looper" which utilizes \@tfor: \documentclass{minimal} \usepackage{trace} \makeatletter \newcommand\looper[1]{% % ...
36
votes
4answers
2k views

How does your mind bend \expandafter to its will?

Expansion is often cited as one of the most arcane aspects of TeX, more akin to witchcraft than to something easily picked up by the newcomer. There are many great questions and great answers about ...
34
votes
1answer
3k views

Is it \catcode or \catcode`?

I've noticed that \catcode is poorly documented in the TeXbook. The primitive is defined as \catcode but every time it is used, it is used as \catcode` ... the backquote is never discussed. ` itself ...
20
votes
3answers
8k views

LaTeX @ (at) symbol [duplicate]

Possible Duplicate: Why do LaTeX internal commands have an @ in them? What does the @ symbol mean in LaTeX? I'm looking at the source of apa.cls, and there's a declaration: ...
42
votes
4answers
1k views

What is “expansion”?

I'm relatively new to (La)TeX, but I have a reasonable amount of experience with computational programming languages. Until I began learning (La)TeX, I'd never heard of "expansion"... So, what is ...
41
votes
3answers
857 views

Why/When should I pay attention to warnings?

I often see warnings in the compilation-log of my tex-files. I searched in the internet and did not find a good answer to this question. And in my opinion there must be a reason why tex warns me about ...
37
votes
2answers
443 views

How to implement (low-level) arrays in TeX

Update: I have revised my question based on the comment by Bruno Le Floch and some further research. As some may know, I'm implementing a huge TeX macro package which has to do a lot of internal ...
25
votes
4answers
561 views

Why isn't a command defined by \newcommand with an optional argument expandable?

In trying to fix a problem with a nested macro repeatedly calling itself, I tried expanding the inner call before passing it as an argument to the outer one. This failed miserably because the macro ...
21
votes
6answers
754 views

LaTeX Markup Options?

I was wondering what prevented the implementation of a MarkDown system in (La)TeX? I know that pandoc does a conversion of MarkDown with extra features to LaTeX. I also know that many are happy with ...
21
votes
5answers
980 views

More Modern Reimplementations of TeX

There is no doubt that the original Pascal/WEB implementation of TeX is a masterpiece and I have learnt a lot reading through the source code (both weaved and tangled) but it definitely shows its age. ...
19
votes
3answers
526 views

Whatsits: when are they used in practice?

This question came up in discussions surrounding the question How to replace a large block of text by an empty block of the same size?, which basically asks for a vmode analog of \phantom. My question ...
31
votes
2answers
692 views

No \makeatletter required?

In typing up some small examples that might create errors in LaTeX (for Documents with typical LaTeX errors), I tried the following: \documentclass{article} \def\my@macro#1{-#1-}% This is magic ...