{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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11
votes
3answers
278 views

Expandable 'character scanning' command that preserves spaces

David Carlisle recently offered a clean and rather elegant TeX solution to a question about expandable 'character scanning' commands. Unfortunately, David's solution does not preserve spaces in the ...
11
votes
5answers
658 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 ...
11
votes
5answers
1k 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}% ...
11
votes
3answers
169 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 ...
11
votes
4answers
110 views

A question about macro matching

Consider the following macro definition, and subsequent invocation: \def\foo #1 #2 \bar{stuff with #1 and #2 goes here} \foo arg1 arg2 \bar The \bar simply acts as the terminator for \foo. This all ...
11
votes
1answer
156 views

(Re)definition of commands that use delimiters other than braces (e.g. \underbrace)

How do you go about redefining a command such as \underbrace, which uses an "uncommon" delimiter, i.e. _, between its two arguments, so that the redefined command be usable in exactly the same way as ...
11
votes
3answers
500 views

How to display only certain lines of a paragraph?

From reading Knuth's TeX Book (Chapter 14 How TeX Breaks Paragraphs into Lines), I understand that entire paragraphs are read in and then "massaged" by the "line-breaking algorithm" in an optimal way ...
11
votes
3answers
269 views

List (at run time) the macros that are currently defined

TeX of course knows at any time what control words and symbols are defined. Is it possible to access this information, for example at the end of a run? Edit: the answer for pdfTeX is no, since the ...
11
votes
1answer
475 views

Using \toks registers

I was reading this tutorial for TeX programming: http://pgfplots.sourceforge.net/TeX-programming-notes.pdf recommended in the 2-nd answer here: Where do I start LaTeX programming? It says: ...
11
votes
1answer
540 views

Consume/absorb a token

How does consume/absorb/remove a token from then token stream in TeX? I'm using @ifnextchar and would like to remove the character it matches.
11
votes
1answer
136 views

Begin/end a logical block?

Can I create a logical block (like HTML div element), so I can apply features like \centering locally, but not affect the outside environment?
11
votes
2answers
736 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 ...
11
votes
1answer
2k 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, ...
11
votes
1answer
604 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 ...
11
votes
1answer
241 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? ...
11
votes
1answer
977 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 ...
11
votes
1answer
663 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 ...
11
votes
1answer
142 views

XeTeXpicfile in vertical mode

Given a minimal like \line{% \vtop{\hsize=.6\hsize Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse tempor lectus sit amet laoreet convallis. Quisque at est lacinia, porttitor ...
11
votes
2answers
404 views

Difference between unrestricted and internal vertical mode

At any point in the processing of a document, TeX can be in one of seven modes: no mode (only in \write and similar commands, I think), math mode ($...$), display math mode ($$...$$), restricted ...
11
votes
2answers
123 views

increase \hyphenation{word1 word-2…} capacity

We use LaTeX to typeset a large collection of books with many proper names. We use the \hyphenation{word1 word-2...} command to specify words that should not be hyphenated and to suggest hyphenation ...
11
votes
1answer
237 views

TeX capacity exceeded, sorry [semantic nest size=500]

Reading through tex.web, I note that there is a difference between grouping levels and semantic nesting (i.e., the nesting of math, horizontal, and vertical modes). I can think of commands which ...
11
votes
2answers
182 views

What combinations of mode and \currentgrouptype exist?

I am trying to predict in any given situation what TeX does if a closing brace reaches its stomach (apart from reverting local assignments). For instance, \vbox{\tracingall H} shows that if it is in ...
11
votes
2answers
133 views

Is there any reason to define a zero-argument macro using a starred defining command?

Is there any reason to define a 0-argument (read: zero-argument) macro with a starred command (\newcommand* instead of \newcommand or \DeclareRobustCommand* instead of \DeclareRobustCommand)? After ...
11
votes
1answer
749 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 ...
11
votes
1answer
139 views

How many different concepts of “token equivalence” are there in TeX?

I was living in the delusion that the "token equality" tested by \ifx was the only thing you need to remember about this subject, but this week I learned otherwise (thanks to David Carlisle). Now ...
11
votes
1answer
76 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 ...
10
votes
3answers
389 views

Why is tex designed to render spaces around brackets?

When I wrote following lines: \section{Introduction}{ Content in introduction ... } Unwanted space comes before Content as warned. I understand it's due to some technical decision in tex. But I ...
10
votes
4answers
453 views

Extract first, last and rest of tokens

This question is related to Extract first & last characters of macro argument?. It seems that if, besides getting first and last tokens, one wants to accumulate the rest of the tokens, the ...
10
votes
3answers
621 views

Check for empty macro argument

There is a description on how to check whether the argument of a macro is empty in What does \ifx\\#1\\ stand for? Unfortunately, I can't get any of the examples there to work. Among others, I have ...
10
votes
2answers
241 views

All (La)TeX warnings and errors

For testing purposes, I am looking for a comprehensive list of all errors and warnings that TeX, and LaTeX can output. I don't mean errors and warnings produced by all packages, as this would give an ...
10
votes
2answers
586 views

How to get the catcode of a token?

For debugging a complicated macro I would like to print out the catcode of a token. Optimally I would like to have a macro \getcatcode such that, for example, \getcatcode{a} would expand to 10. How ...
10
votes
2answers
84 views

\csname not working as expected

The following code prints ==atname== \def\atname{atname} \def\xxx{name} \def\at{at} ==\csname\at\xxx\endcsname== \bye but this does not: \def\@name{atname} \def\xxx{name} \def\at{@} ...
10
votes
2answers
851 views

How to include eps files in Plain TeX? [duplicate]

The title stands for itself. If it is not possible, how does LaTeX import an EPS file using \includegraphics?
10
votes
2answers
156 views

Why is \newcount declared \outer?

I'm a user primarily of Plain TeX. Lately I get annoyed about the \outer nature of \newcount, especially when I write macros which require temporary internal variables, variables which really need not ...
10
votes
2answers
277 views

Catcode of \endlinechar when its charcode is less than 1

When \endlinechar is less than 1, how do we access its catcode? The following gives the error shown below: ! Bad character code (-1). l.34 ...ndlinechar\string=\the\catcode\endlinechar ...
10
votes
5answers
540 views

What is the minimum TeX one can use to put together a mathematical document?

Being a mathematician, I use LaTeX a lot for writing. However, I am interested (mildly) in working with TeX instead, even if only for keeping my own notes. What is the minimum amount of TeX do I need ...
10
votes
2answers
189 views

Execute non-expandable code inside a tabular environment

As there is no Expandable version of \InputIfFileExists or \IfFileExists, the question arises whether it is possible to execute non-expandable code in a tabular environment after all: File main.tex: ...
10
votes
4answers
991 views

Generalize \@ifnextchar to consider more than one character.

I am looking for a clever way to write a switch statement based on the next input characters, ideally, one could write: \@switchnextchars \@case{abc}{\typeout{You gave me an abc}}% ...
10
votes
3answers
879 views

`\write` non-printable ASCII characters to a file

\immediate\write\SomeStream{x} writes x to the file open in \SomeStream. I would like to write non-printable ASCII characters, such as ``, to a file. My naive guess is \begingroup %To keep ...
10
votes
2answers
211 views

Determining the math class of a non-keyboard symbol

What is the "right" way of determining the math class (e.g. ordinary/0, relation/3, closing/5, etc.) of a non-keyboard symbol? Something like \oplus is easy enough to guess, but I wasn't immediately ...
10
votes
1answer
109 views

TeX doesn't recognize built-in control sequences?

I'm trying to learn to build things from the ground-up with TeX (not LaTeX---I've used LaTeX before, so I know how easy a solution "\usepackage{amsthm}+\begin{theorem}" is) and I'm trying to build my ...
10
votes
1answer
144 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 ...
10
votes
1answer
344 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 ...
10
votes
1answer
79 views

How to define a command using \lowercase in \csname

I was being lazy and had a lot of commands of the form \def\foo{...Foo...} So I was thinking about taking an approach like ...
10
votes
2answers
449 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 ?
10
votes
1answer
270 views

What documentation thoroughly explains how to use TeX conditionals?

I have a document which needs a large variety of plain TeX conditionals, e.g.: IF #1 >= 1 AND #2 >= 10 IF #1 != “tree” OR #2 == “mountain” IF 10 > #1 > 2 I have found limited ...
10
votes
1answer
133 views

Emulate TeX's grouping

In TeX, various kinds of groups must match properly, for instance, the following is wrong: $ \begingroup $ \endgroup I would like macros which allow such mismatched grouping. They would keep ...
10
votes
1answer
213 views

Making a character active vs assigning it a specific catcode

My query arises from my answer to Tab not as extra alignment tab and Andrey's rather nicer version. The question at hand involved making the TAB character usable for aligning tables. I assigned it to ...
10
votes
1answer
82 views

\toks register expansion issue - or is it?

I am trying to assemble a table that occurs multiple times throughout a document. It always consists of some fixed columns, followed by a set of columns that appear in one table but are not needed in ...
10
votes
1answer
189 views

How to install or replace fonts in old TeX files?

I got interested in a research paper from 1991, which I cannot get an electronic online version of. The author was kind enough to send me his tex sources, but is himself unable to produce a pdf file ...