{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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9
votes
1answer
109 views

Macro parameter delimited by more than one delimiter

TeX user can simply create the macro with a parameter delimited by an arbitrary sequence of tokens. For example \def\macro #1delimiter{...#1...} Is it possible to create a macro with a parameter ...
25
votes
1answer
114 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 ...
19
votes
2answers
452 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 ...
2
votes
1answer
36 views

How to expand a LaTeX counter when adding to token list

In short: I am trying to append counter values to a token list, but when I print the token list at the end I get the final values of those counters. What I want is the value of the counters at the ...
4
votes
2answers
130 views

Would it make sense to write a TeX algorithms implementation in Cairo/Pango, so that it can be used to output anything Cairo can?

What I'd like to do is experiment with a TeX renderer, and write it in a good graphics library, which includes font support, so I ended up with Cairo. Does it make sense to write a typesetting ...
32
votes
4answers
640 views

How does a TeX engine read and render the input stream?

I am new to TeX programming and I have not finished reading the TeXBook yet. I need at a glance tutorial about how a TeX engine reads, processes, and produces its output. My mental model as a newbie ...
7
votes
3answers
188 views

Arguments possibly delimited by \bgroup and \egroup

I still don't see (and haven't thought about) pros and cons of making available the arguments as \foo{…} or \foo\bgroup …\egroup (or even unbalanced, \bgroup …} and {…\egroup). But I'm curious about ...
15
votes
2answers
164 views

\expandafter with \uppercase ordering

As I understand it, the behavior of \expandafter is such that if \a and \b are macros, then \expandafter\a\b will first expand \b then \a. But my understanding must be wrong, because I don't ...
49
votes
5answers
857 views

\let\foo\bar vs \let\foo=\bar

Both uses of the \let primitive often lead to the same result. Is this even true for every case? What was the thought process behind it. And if they are actually not equivalent, are there particular ...
17
votes
4answers
466 views

Scaling a glue in TeX

is there a possibility to scale a glue in TeX? Consider the following example: \newskip\foo \newskip\bar \foo=10pt plus 2pt minus 3pt \bar=2.5\foo\relax \showthe\foo \showthe\bar \bye When ...
5
votes
4answers
192 views

A simple line from start of the page to the end

I need on one specific page a line from the very top to the end of the page (it is for folding). Everything I tried so far stopped at the head/foot room. Someone got an idea?
1
vote
0answers
52 views

Geometry package in TeX: How to print (or use) the values of geometry properties in document page?

I have problems with geometry package. I would like to find out parameters of my page (layout) such as textwidth, layoutheight etc. I want to have a dynamic layout of my page without number or ...
79
votes
2answers
5k views

What are penalties and which ones are defined?

Very often you can find solutions by changing the penalty. One is widowpenalty. However what are penalties and is there a small list of every defined penalty. There is a German site which does ...
32
votes
3answers
774 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 ...
4
votes
1answer
966 views

TeX capacity exceeded, sorry [save size=50000]

I am on Mac OS X Lion latest, and get the error trying to compile my large multi-page project. This happens after adding one more code listing (shown below). The full error is: TeX capacity ...
6
votes
2answers
140 views

Delimited arguments and using a macro inside of itself

I wanted to play with delimiter sizing without using the \delimiterfactor, -shortfall, etc. and made the following: \newdimen\bigdim \bigdim = 1.9743ex \newdimen\Bigdim \Bigdim = 2.671ex ...
25
votes
3answers
288 views

Has a command access to its own name?

Can two commands - where the one is a copy of the other so that \ifx gives true - have different behaviour depending on the actual name used for a call? \documentclass{article} \newcommand\red{some ...
12
votes
7answers
2k 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 ...
5
votes
1answer
46 views

\par in the parameter text (as an argument delimiter) and \vbox{#1} in an \everypar macro

This is basically a question about TeX's error messages. I am confused by a cryptic error message that TeX gives me when I try to do the above. I have tried to isolate it, but have come no further ...
6
votes
1answer
65 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
27 views

Page breaks and memory [duplicate]

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
52 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
879 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
597 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
116 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
42 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
126 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
79 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
49 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 ...
61
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
174 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
627 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
152 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
64 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
109 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
44 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
65 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
188 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
36 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
72 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
84 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
56 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
106 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
224 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
769 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
48 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 ...