{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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42
votes
4answers
7k views

How to check if a macro value is empty or will not create text with plain TeX conditionals?

I have a macro which holds some text value, e.g. \macro{some text}. If it is empty, I would like for nothing to appear in the document, but it has some content of any kind which would produce text ...
16
votes
1answer
286 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
499 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
764 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
63 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}} ...
15
votes
4answers
770 views

File copy without expansion

What is the command for file copy? I want to copy the contents of one file into another without any command expansion. In a command line driven operating system one would use copy source target I ...
8
votes
1answer
182 views

Why do I need an \hbox inside \vcenter to make it work?

I want to vertically center an object in an equation. I thought: "Ok, \vcenter is the way to go." But I don't understand (not even from the TeX primitives reference), why I need an \hbox inside my ...
7
votes
2answers
154 views

How to show dimension values in scaled points

TeX stores dimensions internally in scaled points but operation \the expands to the corresponding value in points. Can we avoid the conversion and get the more precise, "original" value instead?
7
votes
1answer
270 views

How many man-years does it take to implement TeX?

When I first posted messages to comp.lang.postscript about my efforts to write a postscript interpreter I was informed that it takes approximately 5-10 man-years to write a fully-compliant level-3 ...
10
votes
4answers
154 views

# in conditionals in alignment tabs?

I am looking for ideas how to make TeX understand that when # appears both in the if-else and in the else-fi part of a conditional in an alignment tab, in the end there will never be more than one # ...
2
votes
2answers
61 views

Passing the value of a register as a macro argument

I'm looking for a solution to the following problem: \def\m#1{{ \dimen0=200pt \#1=\the#1 % Outputs 200pt rather than 100pt }} \dimen0=100pt \m{\dimen0} EDIT: The code sample above ...
8
votes
1answer
135 views

Incomplete \iftrue is valid input?

Is LuaTeX beta-0.79.1 correct in thinking the following is valid input: \iftrue \bye
9
votes
1answer
81 views

Namespace in luatex

Is it possible from luatex access registers where all names of command sequences are stored. Is it possible to pull out this list of names? I am looking for a way to trace how namespace changes during ...
5
votes
2answers
163 views

New primitives and grammar for replacing horrible \expandafter

Time and time when I am trying to read or write some macros, I'm always frustrated by lots of \expandafters inside them. Why don't we add some new primitives and grammar into TeX engines to make ...
13
votes
2answers
233 views

ifx, macros and grouping

I do not understand how \ifx interacts with macro definitions. Here is a minimal example: \def\a#1{\b} \def\b#1#2{[#1:#2]} \a ABC The output is [B:C], as expected. If I change the definition of \a ...
7
votes
2answers
166 views

\xrdef and \xref in eplain

I tried to upgrade eplain used in the book "TeX for the Impatient" from version 1.9 to latest version 3.6, but came across the following problem with new eplain. The follwing code could be compiled ...
5
votes
1answer
83 views

Is it possible to conditionally execute statements based on the translating engine, within Plain TeX?

Note that this question is about Plain TeX, not LaTeX. Consider the following example. \pdfpagewidth 8.5 in \pdfpageheight 11 in foobar \bye Under pdftex, this will work fine. However, this will ...
3
votes
1answer
90 views

Is there a platform-independent way of specifying page dimensions in TeX?

This is partially a follow-up to this question since the answer mentioned tex as executing the "original Knuth TeX". So far, I have seen that the following will work in TeX, but is ignored by ...
1
vote
0answers
140 views

List of TeX internal parameters? [closed]

I have come across quite a number of TeX internal parameters, like \clubpenalty, \widowpenalty, \abovedisplayshortskip and so on. Could you provide me with a complete list of them, what they are for ...
8
votes
2answers
285 views

Conversion of tex to latex

Quite surprisingly for me, I did not find valuable information on how to convert plain TeX files to LaTeX documents. There is a TeX.SX question, but it was answered with a particular solution. I ...
14
votes
1answer
641 views

What is the command \span?

I have bumped into the \span primitive a couple of time. I got the impression it is defined in the TeX program, not even in plain.tex. Is that right? And what does that command do and what is it for?
8
votes
2answers
103 views

Why is the character following this macro-defining macro gobbled up?

I have the following plain Tex code: \def\xx{ABC} \def\temp #1 {\def\tempii{#1}} \temp\xx a b c \tempii\tempii I expect to see the following output: a b c ABCABC But I actually see this: b ...
16
votes
2answers
385 views

Filling gaps by repeating a character

I want to create a macro like \mymacro that has four arguments; first and fourth arguments are any letters, second argument is a character and the third argument is a length. When I say \mymacro{م} ...
8
votes
2answers
93 views

badness for lines without glue?

I want to typeset a special paragraph which have some penalty items inside it but no glue. TeX always produces an overfull box for this paragraph. I have two questions: What is the line badness if ...
3
votes
2answers
122 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 ...
5
votes
1answer
60 views

polyglossia + output routine = wrong expansion in file writing (???)

If I use the following custom class: \NeedsTeXFormat{LaTeX2e} \ProvidesClass{upecha}[2014/09/21 v0.8 tibetan modern pecha class] \input{size11.clo} \def\@outputpage{\shipout\vbox{\box\@outputbox}} ...
10
votes
1answer
206 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 ...
4
votes
2answers
261 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 ...
33
votes
4answers
729 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 ...
8
votes
3answers
249 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
191 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 ...
50
votes
5answers
950 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 ...
18
votes
4answers
508 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
200 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
67 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 ...
85
votes
2answers
7k 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 ...
34
votes
3answers
972 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
1k 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 ...
7
votes
2answers
166 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
307 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 ...
14
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
88 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
218 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
57 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: ...
51
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
1k 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 ...
21
votes
2answers
669 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
126 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
276 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}