{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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2
votes
1answer
180 views

Implementing the Sum Function in TeX

How would I go about implementing a function in TeX to add an arbitrary number of numbers? Reading through the \def notes, it seems it can only take up to nine arguments. How would I make a function ...
0
votes
0answers
46 views

Where is this TeX magic line “%&” documented? [duplicate]

I learned about this magic %& line that is supposed to hint at the flavour of TeX a file is using. Where is this magic documented? I have not been able to find it anywhere.
111
votes
10answers
8k views

Why is LaTeX so complicated? [closed]

I have been using LaTeX professionally almost every day for almost 10 years, so I think I can say that, by now, I more or less know what I'm doing. I also do a lot of ordinary computer programming, in ...
5
votes
1answer
251 views

TeX at the Command Line

How does TeX work at the command line? More specifically, after having installed LaTeX, I found that typing tex in the command line opened up an interpreter. However, I have no idea what I can do ...
3
votes
4answers
212 views

Conditional \end or \bye in TeX (plain-tex)

Can someone figure out a conditional \end or \bye in TeX-Code? (plain tex) I want to put in several lines into a TeX-file, each ending with \end , to be compiled before the document is complete, to ...
5
votes
1answer
176 views

Macro in Tex Programming

I am confused whether the below macro is for section or what? If yes can anybody help me to explain this piece of code \def\Section #1 \par { \bigbreak\vskip\parskip \need 1.5 in ...
17
votes
0answers
228 views

Test if paragraph has an overfull line

I'd like to test if the last paragraph has any overfull line. The naive approach of looking at the \badness once the paragraph is finished does not work, as it will only give the badness of the last ...
1
vote
0answers
178 views

TeX Programming [duplicate]

I have lot of confusion regarding TeX and LaTeX. What I have understood is TeX is basically macro instructions, and LaTeX uses that macros or we can say TeX is extended to LaTeX. But, really not very ...
2
votes
1answer
104 views

Are there any ways to embed LaTeX source code from a PDF file [duplicate]

I want to the tex files from PDF files. I have the PDF files that I get in Internet and have a lot of mathematics, so I want to convert PDF files into tex files. I researched in these forum, and ...
6
votes
2answers
188 views

Macro expanding to a file's contents?

How can I define a macro so that it expands to a file's contents?
6
votes
1answer
86 views

\unskip and \hskip in \linebreak

I found the definition of \linebreak macro as follows: \def\linebreak{\@testopt{\@no@lnbk-}4} \def\@no@lnbk #1[#2]{% \ifvmode \@nolnerr \else \@tempskipa\lastskip \unskip ...
11
votes
1answer
180 views

What is the difference between a typesetting language and a markup language

I remember, I read some article in a technical journal where the author drew the attention on the reader on a lot of people confusing typesetting languages and markup languages. How can I surely tell ...
6
votes
2answers
184 views

How to make latex parse `x` as an argument of a macro definition instead of `#1`

When I define a mathematical function for plotting in pgfplots or pstricks I usually to it in the following way: \def\f(#1){(#1)^3 + 3*exp(#1)} just as suggested by Jake in his answer to a ...
10
votes
2answers
366 views

TikZ/TeX: Minimum line width/maximum resolution

I would like to employ TikZ for some constructive work, namely, programming a FabLab laser cutter. This nifty device gets a 2d drawing (as PDF) and cuts along all hairlines in the PDF. A harline is ...
10
votes
2answers
109 views

\prevdepth and \noalign

In The TeXBook it says The value of \prevdepth at the time of the \halign is used at the beginning of the internal vertical list, and the final value of \prevdepth is carried to the enclosing ...
12
votes
3answers
407 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 ...
9
votes
3answers
231 views

Why in the discussion of the definition of \newif are the following things true

This is a couple of questions that stem from the answer to Problems understanding definition of \newif by @egreg. In that @egreg says Let's look at \expandafter\expandafter\expandafter ...
7
votes
3answers
172 views

How can I display the possible hyphenation points for words in a language other than US English?

This is a follow-up to tohecz's question, which I'm asking at the suggestion of Mico. The original question asks how to discover the hyphenation points for particular words, and the answers explain ...
7
votes
2answers
308 views

Input/Output primitives of TeX

I'd like to write some simple macros for handling things like cross-reference, to use them in plain TeX. (I know there are already macros devoted to this, like the ones present in Eplain, but I would ...
13
votes
2answers
289 views

How are dashes implemented in TeX?

How does LaTeX implement the differences between the dashes? -, --, and --- all print different dashes, but - is not an active character: it has catcode 12, the same as digits like 2.
17
votes
2answers
352 views

When is \relax necessary after a \ifcase#1 statement

In the LaTeX kernel (latex.ltx) we see some examples of \ifcase#1\or a\or b\or ... (an \ifcase without an added \relax), but when we look at some packages most of them add this statement after the ...
7
votes
1answer
178 views

When to use {} to address an argument

When is it necessary to use {} to squeeze an argument to a command? Example: In TeX we see a lot of calls like \vskip\onelineskip while this macro (\vskip) is defined to take one argument. Would it ...
9
votes
1answer
119 views

line breaking mystery in `\@dottedtocline`

I'm trying to understand why some entries in a table of contents are overfull even if a sensible break points exist. I pulled down the problem (and the definition of \@dottedtocline) to this example: ...
3
votes
1answer
71 views

Why does \the\day not work in my macro?

(TeX-Code!) I have defined a TeX-macro to compare date and time values. Everything works well, until I put in \the\day, to call the current value of it. Can someone imagine, why this works with all ...
5
votes
3answers
146 views

Delimiting-a-macro-with-itself-chain

Reading this question and the answer of @Werner made me think about if it is possible to have chains of self-delimiting macros like \XX abc \XX def \XX xyz or lets say \begin{someenv} \XX abc \XX ...
0
votes
0answers
29 views

Always creating a second document with slightly different configuration [duplicate]

I work on a document, and I would like to create, simultaneously, another document which has the 'doublespacing' tag on. Until now, every time I needed it, I just copied the TEX file to a ...
4
votes
1answer
103 views

A certain alignment for displaying systems of linear equations

I have several equivalent systems of linear equations that the following code displays. I would like to have them vertically aligned at the equals signs. I found the following code on this web site ...
9
votes
2answers
224 views

Replace every backslash in a string with a forwardslash

I would like to replace every backslash \ inside a macro (string) with a forwardslash /. The macro is intended to contain a filename in Windows notation which should be replaced by a valid (La)TeX ...
1
vote
1answer
67 views

How to parse a macro that contains a \let?

My situation is similar to, but hopefully different from How do I ‘expand’ a control sequence \let to a character?, as that question does not admit a positive answer. I want to parse, not expand, but ...
5
votes
1answer
98 views

Accessing child contents of LaTeX boxes (append/concatenate TeX box material)?

This is somewhat similar to Reading the contents of a box, but with a specifically plain Latex example; I somewhat solved the question while writing the post, so I'll formulate the question like this: ...
5
votes
1answer
119 views

Per-word info needed in DVI to create touch rectangles on LaTeX documents in iTeX for the iPad

When reading a LaTeX document on an iPad with iTeX, I need to know the position of every word on the page. (I also need to know the positions of images, URLs, footnotes, etc., but they are all ...
21
votes
5answers
3k views

What on earth is iTeX?

Is that an hoax? Or is it a real wish from D. Knuth? (http://river-valley.zeeba.tv/media/conferences/tug-2010/Don-Knuth)
4
votes
3answers
188 views

Safe test for an empty expanded macro argument?

How can I test in a safe way (i.e. without reserving tokens as explained here) if an expanded macro argument is empty?
11
votes
3answers
442 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 ...
6
votes
1answer
113 views

Empty argument to \string

What is the result from \string{} and why can't we use it in place of \detokenize to check if a macro argument is empty as explained here?
6
votes
1answer
75 views

How to return \count value from \def

I wrote a macro which calculate remainder : \def\remainder#1#2 {% \newcount\dividendcount \dividendcount=#1 \newcount\quotientcount \quotientcount=#1 \divide\quotientcount #2 ...
1
vote
1answer
43 views

Could not use \rule in chapter title in latest texlive

Using XeLaTeX In texlive 2014 (versions before May or texlive 2013 or older), one can use \rule{width}{height} in a chapter title. However, in latest texlive (versions after June) form ctan, use of ...
8
votes
2answers
172 views

Active space character without definition?

In the code below, why does the space character not produce an 'Undefined control sequence' error as the dot character does: \catcode` =\active \catcode`.=\active a b a.b \bye
18
votes
4answers
4k views

How to compile the source code of TeX

I am more and more interested in the system TeX (and LaTeX) and I want to study it more deeply. I am not telling that I want to learn how to use it, but I want to understand its mechanism now. The ...
20
votes
1answer
178 views

How to delay a command execution until the next hmode?

I want to write an environment which adds a marginnote at the begin. The problem is that I can't control the content of the enviroment and so the placement of the marginnote varies a lot. How could I ...
28
votes
3answers
292 views

Is there a way to get at the value of \prevdepth from the main vertical list inside the output routine?

To motivate that (admittedly) strange question: When TeX builds a vertical list it keeps track of the depth of the last box added in a special variable called \prevdepth which is used to calculate ...
5
votes
1answer
59 views

The value of \hsize in ams classes is 0pt in the preamble

\documentclass{amsart} \showthe\hsize \begin{document} ... \end{document} returns 0pt but \documentclass{amsart} \begin{document} \showthe\hsize ... \end{document} returns 360pt. Is the first ...
4
votes
2answers
55 views

Compensating for multispan boxes wider than spanned columns

The code below produces a horizontal alignment with two columns and three lines (see first image below). The first column has its elements flush right and the second column has its elements flush ...
19
votes
1answer
984 views

Why are the latex, pdflatex and pdftex binaries identical?

I apologize if this question is somewhat off-topic but I think that this is the best place to find an answer. This is sort of an oddity that's confused me for years. When I run latex -v I get: ...
3
votes
1answer
257 views

Positioning of \hrule and \vrule

I try to construct a symbol from 4 rules, one horizontal and three vertical ones. \showoutput gives me the correct dimensions for all of them (see below). However, the horizontal one somehow ...
0
votes
0answers
355 views

Weird behaviour in Texmaker (Changing the papersize) [closed]

I'm trying to change the page size in a tex document (I want a letterpaper size). I'm using Texmaker and the sequence Latex -> Dvips -> ps2pdf and my code is \documentclass[letterpaper]{report} ...
16
votes
1answer
293 views

Ligatures and hyphenations: the effect of empty brace groups {}

For the following example, \hsize =2in shelf{}ful shelf{}ful shelf{}ful rot{}ten rot{}ten shelf{}ful shelf{}ful shelf{}ful shelf{}ful shelf{}ful rot{}ten rot{}ten shelf{}ful shelf{}ful \bye The ...
14
votes
2answers
527 views

Why using character ^^ff before every chapter in the TeXBook source

When viewing the source code of the TeXBook, I find that there is a character ^^ff before every chapter in it. I am wondering why using this ^^ff character which seems useless? The following ...
26
votes
2answers
826 views

Why does a TeX point differ from a Desktop Publishing point?

From this answer to Why does PDFLaTeX and XeLaTeX generates 11.955 font size for 12pt documentclass option?, I found out that PDF and TeX have different ideas about the size of the point (pt). A TeX ...
4
votes
1answer
66 views

\halign does not affect \prevdepth?

What is the purpose of restoring the initial value of \prevdepth at the end of a horizontal alignment: \prevdepth=.1234pt \everycr{\noalign{\dimen0=\prevdepth prevdepth in noalign: \the\dimen0}} ...