{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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4
votes
1answer
34 views

testing parameter values with \ifx

Let's say that I would like to redefine \@seccntformat so that whenever the section counter is printed, it is prefixed by Section, but other counters should no be changed. Here is my failed attempt: ...
2
votes
0answers
24 views

Page breaks and memory

Note the following passage in the TeXbook (p. 110) TeX breaks lists of lines into pages by computing badness ratings and penalties, more or less as it does when breaking paragraphs into lines. ...
1
vote
1answer
51 views

Vertical bar appearing except on top of page

I want a command \shybar which prints a \textbar except if it would be the first character on the page. In this case, it should do nothing. Because of this question, I tried the following code: ...
49
votes
3answers
1k views

Advantages and disadvantages of fully expandable macros

As I currently understand them, fully-expandable macros are analogous to pure/effect-free functions in functional programming. Correspondingly, things that are not expandable, such as \def, are ...
9
votes
4answers
831 views

Writing Roman numbers in Equation

What is the command for writing roman numerals like I, II, IV etc. in an equation ? To be noted that my requirement is to write them within $$ ...$$ and not as counters or page numbers. Any light on ...
20
votes
2answers
583 views

The role of %&latex at the beginning of a source latex file

Could someone please explain what is the role of %&latex which is put in a source LaTeX file before \begin{document} command?
6
votes
1answer
110 views

Stopping the accidental absorption of digits into literals

I recall that I was once writing some TeX code, and I encountered something like this \count\foo \foo=2\otherMacro [\the\foo] If \otherMacro was defined as something like \def\otherMacro{9 cats is ...
7
votes
4answers
260 views

Removing duplicates from a list

Is there a LaTeX kernel command to remove duplicates from a list? The list has the structure \def\alist{john,mary,george,australia,australia}
0
votes
1answer
30 views

Automatic parsing/extraction of single-argument commands from input (for use in new environment)?

I'm not sure whether this is in principle possible, so let me try to explain; consider this MWE: \documentclass{article} \usepackage[showframe]{geometry} \usepackage{tikz} \usetikzlibrary{calc} ...
9
votes
6answers
1k 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 ...
9
votes
1answer
116 views

vbox disappearing inside hbox

I don't understand why a vbox disappears when it's surrounded by two \hss, for instance in: \hbox to 0pt{\hss abc\hss} \hbox to 0pt{\hss\vtop{def}\hss}% doesn't work \hbox to 0pt{\vtop{ghi}\hss}% ...
11
votes
1answer
73 views

Measure total glue in a box

Someone gives me a box, and my goal is to know as much as possible about the amount of glue inside that box. I can assume that the box is not huge, but it may contain arbitrary stuff (so I cannot ...
6
votes
2answers
45 views

What Pascal procedure inserts \mathon and \mathoff?

TeX surrounds inline math formulae with \mathon and \mathoff, which appear to be nodes. For instance, running TeX on $ $\showlists\bye gives ### horizontal mode entered at line 0 \hbox(0.0+0.0)x20.0 ...
32
votes
3answers
734 views

Why doesn't TikZ's \foreach iterate over the last element of the list?

This code \documentclass{report} \usepackage{tikz} \begin{document} \begin{tikzpicture} \draw[dashed] (1,-1) -- (1,2) node[above] {$1$}; \draw[dashed] (2,-1) -- (2,2) node[above] {$2$}; \foreach ...
60
votes
2answers
9k views

When should one use \begingroup instead of \bgroup?

Is there ever a case when the use of \begingroup is preferred to \bgroup? Obviously, \bgroup is necessary in cases where you need to have balanced braces and thus cannot use {, but when is it ...
11
votes
3answers
163 views

Command delimited by return or blank line

I have this document \documentclass{scrartcl} \long\def\quotenextparagraph#1 {\begin{quote}#1\end{quote}} \begin{document} Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod ...
14
votes
2answers
626 views

Active characters let to a (non-active) character

It seems that if I \let\amp&, the alignment tab & can be replaced by \amp everywhere (e.g., in the preamble and in the body of an \halign). It is also possible to make the character & ...
5
votes
3answers
147 views

Trim braces from macro content

I'm having macros with a content which may or may not have extra curly braces. I want to trim the extra braces but without expanding the rest of the content, if possible. The following code shows the ...
8
votes
1answer
61 views

weird ifnum with compact syntax [duplicate]

In some packages like tabularx, I find the following syntax in many places {\ifnum0=`}\fi or even \ifnum0=`{\fi} But I can't figure out why this can be useful for? Is ` a register of some kind? ...
5
votes
3answers
102 views

Adding a hrule between hboxes decreases their vertical distance

Using pdftex. Given two sample programs test0.tex \vbox{ \hbox{X} \hbox{Y} } \bye test1.tex \vbox{ \hbox{X} \hrule \hbox{Y} } \bye gives the following outputs. test0.png test1.png So, ...
4
votes
1answer
43 views

How do you define a command to select nested groups?

Assuming a pair structure (2-tuple) is defined using groups {{<tokens1>}{<tokens2>}} is it possible to define a command \first#1{...} (and \last#1{...}) taking the surrounding group as ...
5
votes
1answer
61 views

Struggling to define variable using variable previously defined

new to tikz and am struggling to figure out how to define a variable using variables I have just defined. I think the problem in the code below is coming from the following section: ...
15
votes
1answer
183 views

\def two macros with same name, but different argument syntax

Is it possible to have macros with the same name, but different “syntax”? E.g. we have the primitive \font which could be seen as having 3 arguments(a. without size information; b. giving the ...
3
votes
1answer
34 views

Possible to run a handler / callback function, when a macro (\inputlineno) changes value/definition?

I was thinking about the debugging procedure I went through in How come the tilde ~ sometimes does not behave like non-breaking space? - basically, to find out where did the macro ~ change, I had to ...
1
vote
1answer
62 views

How to derive one TeX-Format from another

Let's say I want to write my own TeX-format for learning purpose, how can I easily derive from plain.fmt (or better xetex.fmt)?
2
votes
0answers
51 views

GNU Readline- like history, for the latex terminal shell?

I find myself more than often willing to use the (pdf)latex shell, and \typeout commands there directly - unfortunately, there is one deal breaker: there is no command line history. I think that in ...
1
vote
1answer
82 views

Why does LaTeX throw an error when I write _ in text mode

Why LaTex return error when I write _ in normal mode (not math mode). Why we have decided to return error, we couldn't just print _. I mean if we write _ in a normal mode it print _ and in normal mode ...
3
votes
1answer
46 views

Why can I not vsplit a parbox? (and fbox alignment, and unvbox syntax)

I was trying to experiment with the code in this answer: Breakable vboxes, and I got something I didn't expect; consider this MWE: \documentclass{article} \usepackage{lipsum} \usepackage{xcolor} % ...
4
votes
4answers
81 views

\vtop vertical top alignment of \vsplit \vbox

Well, I wanted to have a minipage spanning across pages, so first I thought to split a minipage so it can , but I learned you cannot; so I got to breakable vboxes, and in trying that, learned that ...
7
votes
3answers
216 views

How does (or, what happens when) Tex typeset(s) a line and linebreak?

I could not find references to this with a cursory search, so I thought I'd post a question; I'm aware this is probably discussed at length in the Tex book or similar, but unfortunately I don't have ...
34
votes
3answers
737 views

What does the 'etex' package do, exactly?

I was creating a rather large LaTeX project, so I had to use many packages. This gave me an error No room for a new \dimen \newdimen \MPscratchDim while my editor(Kile) opened the file ...
3
votes
1answer
41 views

Variable scoping of edef definitions in a local group (inside an ifx conditional)?

Consider this MWE: \documentclass{article} \def\testswitch#1{ \def\isA{A} \def\firstOpt{#1} \edef\tmpstr{-init-} { % start local \edef\tmpstr{-loc defined-} } % end local ...
7
votes
1answer
204 views

debug No room for a new \write problem

I have a template with an extensive documentation. (See TemplateDocumentation.pdf). It compiled several month ago. Now with updated packages it does not compile anymore because of the famous No room ...
4
votes
1answer
304 views

Generating a catcode table in Latex (with \typeout to terminal)?

I often need to look up a catcode table, and quick searches on the web are rarely satisfying. So I thought, it must be (in the long term) easier to use a Latex function of sorts, to loop through all ...
41
votes
2answers
4k views

What is the basic mechanism for writing something to an aux file?

I am interested in the basic mechanism behind writing stuff to the .aux file. (Or some other auxiliary file). Let's say I want to write myself a basic package for making notes on my files. (I know ...
1
vote
1answer
15 views

how do you put caption on figures in sweave

I have this sweave code. I need to add caption to the figures. I am doing this but it looks like I see the figure before the section{Data ANALYSIS}: \documentclass[letter,12pt]{article} ...
16
votes
1answer
270 views

Semantics of negative glues

This question is about the semantics of glues like 0pt plus -1fill, where the coefficient in front of the fill is negative. The following minimal example shows my attempt to figure this out ...
26
votes
3answers
1k views

Mathematical description of TeX's infinite numbers?

TeX has things like infinitely stretchable spaces and infinitely bad penalties. Since Knuth is Knuth, I assume these are a carefully thought-out implementation of some well defined non-Archimedean ...
6
votes
1answer
175 views

How do I implement a string buffer in TeX?

I've recently learned how to create a macro to iterate over a token sequence using \afterassignment and \let in TeX. Currently, I'm trying to apply this to a tokenization macro (where "tokenization" ...
6
votes
1answer
56 views

Redefine @ for tabular inter-column specification within \makeatletter \makeatother

I need to use a tabular with a @ inter-column specification within a \makeatletter and \makeatother environment. I. e. I something like \makeatletter %code that uses @ as letter ...
5
votes
2answers
39 views

Free - dereference - release - delete a newdimen length?

Somewhat similar to How to erase/delete a counter, I guess, but for \newdimen... So, consider the MWE: \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} ...
1
vote
0answers
44 views

Untyped character at the end of chapter

Although there is no "f" typed, there exists a "f" character at the end of the chapter when pdf is created. What can be the problem? I can't find it! Even I delete all the text, and just type a ...
2
votes
3answers
47 views

Legitimate “local variable” (argument) command in a macro raising “Undefined control sequence”?

Consider this MWE: \documentclass[varwidth,tightpage,border=1bp]{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \makeatletter \gdef\getMyInfoString{% \let\trfm\relax % ! ...
8
votes
1answer
181 views

Maximum number of counters am I allowed to make/have?

I'm currently working on generating the pentest-reports of the company I work for with tex. I came across the totcounter package which I use for the overview table of the findings. there i'm adding ...
0
votes
0answers
24 views

Protecting / escaping the # (number-sign/hash) in a callable macro? [duplicate]

Consider this MWE: \documentclass{article} \usepackage{tikz} % \gdef\myset{ %* \tikzset{ % mystyle/.style={rectangle}, mycode/.code n args={2}{% \typeout{YEAH! #1 #2} % }, } % end ...
5
votes
2answers
75 views

Implicit \hfil at the end of each paragraph?

Why do Alpha \hfil\ Omega\par and Alpha \hfil\ Omega not flush "Omega" to the right?
5
votes
1answer
85 views

Is there any way to disable automatic ('discretionary break') hyphenation, while allowing/forcing TeX to break some chosen words?

I have a large document with narrower paragraph width than regular (approx 5 average words long), and I want to disable hyphenation short of having the opportunity to allow hyphenation of chosen words ...
7
votes
1answer
104 views

How do you define macros to toggle a character active and define a macro for it?

I'm experimenting with core tex in order to learn some basics. My goal is to define a shorthand environment which makes use of active characters. The general idea is to activate the used characters ...
2
votes
3answers
112 views

Left margin wider than right one

Why is the left margin wider than the right one? Each of them should be 1 inch wide: If you run TEX without modifying the plain TEX format, you get pages that are numbered at the bottom; and each ...
4
votes
2answers
77 views

Is it possible to control the minimum tolerance (allowed space between words)

I have learned to use \pretolerance and \tolerance but sometimes TeX decides to "compress" the broken line of text within the paragraph by simply using less space between the words on the line, and I ...