{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
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2answers
685 views

How to use tex -ini, tex -fmt, initex and fmtutil?

What are the roles of each of these commands? What is the good command to create a new format ?
13
votes
2answers
249 views

Difference between one glue and two glues after each other

Is there a difference between A\hskip 1pt \hskip 0pt plus 1fil B and A\hskip 1pt plus 1fil B ? Are these two glues the same in terms of spacing and (line-)breaking? Or do they just add up, as I ...
13
votes
1answer
4k 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, ...
13
votes
1answer
138 views

Difference between “hbox group” and “adjusted hbox group”?

eTeX's \currentgrouptype distinguishes two types of \hbox group types \hbox{\showthe\currentgrouptype} % 3 "adjusted hbox group" \noindent \hbox{\showthe\currentgrouptype} % 2 "hbox group" Looking ...
13
votes
1answer
221 views

Array functionality in TeX?

I've been using LaTeX for a while, but only recently I made myself a mission to create a class. I needed to learn the details of TeX, and I couldn't find answers to some of my questions. One of them ...
13
votes
4answers
501 views

How does one change the math style to one of the “primed” styles?

Background TeX typesets each portion of a mathematical expression in one of 8 styles: display, display', text, text', script, script', scriptscript, or scriptscript'. Knuth calls them, D, D', T, ...
13
votes
3answers
3k 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 ...
13
votes
2answers
195 views

Which TeX procedure removes trailing tabs?

From reading the TeX source, it seems that the input_ln procedure is responsible for removing trailing spaces from lines upon input (before category codes are considered). A very short excerpt from ...
13
votes
1answer
167 views

Does tex know its own command line arguments?

Is it possible to test within the document what commandline arguments were passed to tex? The particular case that prompts this is the question Tabs in output file written by xelatex and pdflatex are ...
13
votes
1answer
1k views

uppercase and \spacefactor

Apparently, \uppercase forgets about the \spacefactor at the end. For example, {What is the spacefactor?} \the\spacefactor. returns What is the spacefactor? 3000. while \uppercase{What is ...
13
votes
1answer
153 views

What is considered a token for non-standard input encodings?

When I use an input encoding to (La)TeX that allows me to directly input characters such as é and ä (such as by declaring \usepackage[utf8]{inputenc}), how is a token defined? Specifically, is it ...
13
votes
1answer
233 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
0answers
153 views

What type of Chomsky hierarchy is TeX? [duplicate]

There are four types of chomsky hierarchy (specified for formal languages): Type-0 Recursively enumerable Type-1 Context-sensitive Type-2 Context-free Type-3 Regular I consider that, it should ...
12
votes
3answers
638 views

How could the macro xii.tex be simplified into a better readable form

I was reading some TeX guides from where I have found this source: \let~\catcode~`76~`A13~`F1~`j00~`P2jdefA71F~`7113jdefPALLF PA''FwPA;;FPAZZFLaLPA//71F71iPAHHFLPAzzFenPASSFthP;A$$FevP ...
12
votes
3answers
415 views

TeX command with argument BEFORE the command

Is it possible to do some TeX magic to get a command \mycmd which takes one argument before the command and one afterwards. So something like <arg1>\mycmd<arg2>. I tried ...
12
votes
4answers
366 views

Ratio arithmetic in plain TeX

I would like to calculate the ratio between two dimensions and produce a dimensionless quantity for use in further calculation in the process. I seem to be unable to do so. Specifically, I run into ...
12
votes
2answers
877 views

Where to find official (!) and extended documentation for tex/latex's commandline options (especially -interaction modes)?

Today I tried to learn more about the several interaction modes for tex/latex/pdflatex etc. The manpages turned out to be not very helpful: $ man tex ... -interaction mode Sets the ...
12
votes
2answers
540 views

How is \unexpanded defined?

I was wondering how \etoolbox's \expandonce does what it does. So I looked up how it was defined and found \unexpanded\expandafter{#1} But no matter where I look, I cannot find a definition for ...
12
votes
2answers
199 views

What would be a suitable replacement for ifcsname in a non-etex situation?

From the pgfkeys.code.tex file: % This is useful: \def\pgfkeys@ifcsname#1\endcsname#2\else#3\fi{\expandafter\ifx\csname#1\endcsnam e\relax#3\else#2\fi}% \ifx\eTeXrevision\undefined% \else% ...
12
votes
5answers
2k 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}% ...
12
votes
3answers
198 views

Useful applications of \edef with macro arguments

Well, it's been in my head for some time, but I haven't got anything out of it, so I ask here. At what places could be useful to have \edef\foo#1{..}? What applications could it have? Is it useful at ...
12
votes
5answers
817 views

Test if token is a control sequence

Sometimes more complex (La)TeX macros test the next input token and branch dependent on its type. I'm aware how to test for catcodes and character codes, but sometimes I like to handle control ...
12
votes
2answers
155 views

Document equivalence

What is the best way to determine, for two arbitrary input files, if they will result in the same compiled document (disregarding timestamp information and external files)? Context I'm attempting to ...
12
votes
2answers
208 views

Can I detect whether a footnote has been split?

Title sez it all: Can I detect, hopefully by inspecting \box\footins, whether a footnote has been split at page-breaking? I found the package fnbreak but it uses labels, which is much too delayed for ...
12
votes
2answers
833 views

Tricks to make macros expandable

Expandable macros are useful (I find working in the lion's mouth super cool). But they are difficult to write. Can more experienced users give hints that help achieve expandability? For example, we ...
12
votes
1answer
205 views

How to get the natural width of the last box in a paragraph?

I want to get the natural width of the last line in a paragraph. For example, the last line of the following paragraph Georg Friedrich Bernhard Riemann (September 17, 1826 – July 20, 1866) was an ...
12
votes
1answer
1k views

Why does \hss fail?

Please why does the following fail? % \hss -> \hskip 0pt plus 1fil minus 1fil \setbox0=\hbox{a}% \setbox0\hbox to 10mm{\hss\unhbox0\hss} \unhbox0 And what makes LaTeX's ...
12
votes
1answer
503 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 ...
12
votes
2answers
466 views

New lines and TeX: difference between ^^J and ^^M

What is a new line for TeX in the following contexts: When reading from a file. When writing to a file. After having read a % character. In a \scantokens. I am asking in particular because the ...
12
votes
1answer
1k views

What is the function of \noalign?

The use of \noalign is quite common. For example here \noalign is used with \vskip{}to control the height of a table cell. How does \noalign work in general, and how does it work with \vskip? ...
12
votes
1answer
857 views

How to prevent extra spaces between two specific words when justification occurs?

My document contains many short, justified lines, so the lines often appear with many spaces between words, e.g.: These words have a space so that they can fit nicely into the available ...
12
votes
1answer
281 views

\show with fewer lines?

I am writing some macros for general debugging purposes (See Yiannis' question). I am basically expanding a given input step by step, and printing the result to the terminal and log. In order for this ...
12
votes
1answer
111 views

Tight connection of \vbox es

I don't understand why TeX put a thin whitespace between my two vertical boxes: \documentclass{article} \begin{document} \vbox to 1cm {\rule{1cm}{1cm}} \vbox to 1cm {\rule{1cm}{1cm}} ...
12
votes
1answer
431 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 ...
12
votes
1answer
171 views

Hide ^^^^-notation from pdftex

The following example gives when compiled with pdflatex the error ! Text line contains an invalid character. \documentclass{article} \usepackage{ifluatex} \ifluatex \usepackage{fontspec} \fi ...
12
votes
1answer
302 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 ...
12
votes
1answer
151 views

Inserting tokens at end of math mode

One can use \everymath and \everydisplay to insert tokens at the beginning of math mode, but what about inserting tokens at end of math mode? Lets say I want to enclose the math mode material in a ...
12
votes
1answer
950 views

Simple un-obfuscation of some LaTeX internals

Here's an example of some code from LaTeX's \DeclareFontFamily: \def\reserved@a{#3} \global \expandafter\let\csname #1+#2\expandafter\endcsname \ifx \reserved@a\@empty \@empty ...
12
votes
2answers
245 views

Assertions in Latex

I am writing a long latex document and use many macros for defining mathematical symbols. I would like to ensure that there is no clash in the notation. For example, something like ...
12
votes
1answer
365 views

Is Knuth's *The TeXBook* complete?

Suppose I want to learn TeX. Then, is The TeXBook a complete source? Does it cover all relevant aspect of TeX? Or is there something worth learning about TeX which is not present there? Does also ...
11
votes
2answers
562 views

() or {} after a command

I was wondering why for some commands it is "(...)" that follows, while for other commands it is "{...}". For example, "\exp(x)" and "\bar{x}". Are both () and {} for specifying the arguments for the ...
11
votes
3answers
271 views

Treating the contents of a TeX-style group ({\blah …}) as macro arguments

I am trying to make adjustments to a large document that uses TeX-style macros, like this: {\defun SomeFunctionName arg1 arg2} The \defun macro is defined as \newcommand{\defun}{\tt}. Can I ...
11
votes
3answers
505 views

Does the \relax side-effect of \csname…\endcsname still have a use?

I find it annoying that using \csname...\endcsname will define ... to be \relax if ... is undefined, and there is no improved primitive that does not have this side-effect, though there are partial ...
11
votes
4answers
243 views

Partially expanding a command

My \john command is defined like so: \def\john{\DontExpandMe} I would now like to repeatedly change its definition, to keep adding some extra stuff on the front. \foreach\i in {ape,bat,cow,dog} { ...
11
votes
3answers
499 views

Understanding etoolbox \ifdefempty and \ifdefvoid

I am trying to understand the etoolbox \ifdefempty and \ifdefvoid macros. The documentation says that \ifdefempty Expands to true if the control sequence is defined and is a parameterless macro ...
11
votes
3answers
445 views

Parser for decimal numbers in (plain) TeX

I need help writing a parser for decimal numbers using only TeX and plain TeX. The set of accepted inputs is given by the regular expression: (+-)?(0-9)*(.,)?(0-9)+ The parser need not do anything ...
11
votes
2answers
145 views

Does a space belong after pt?

Does a space always belong after pt, e.g. as used in \hskip1pt? If a space is used, are there situations where a space will appear where it is not intended? If no space is used, will pt be ...
11
votes
2answers
217 views

Creating new primitives

Consider the following TeX: \tt ~~~[def]: \meaning\def \par ~~~[let]: \meaning\let \par [define]: \meaning\define \par ~[macro]: \meaning\macro \def\macro#1{some ...
11
votes
4answers
481 views

How can I compare two (not necessarily integer) variables?

After experimenting and researching for hours, I still cannot figure out how to perform a simple equality test between two numbers. More specifically, here, the two numbers in question are the ...
11
votes
5answers
500 views

Basics of scanning

I'm trying to master the art of scanning text one character at a time. The following is what I've discovered so far. Is this as good as it gets? I would really prefer not to do all those \edefs as ...