{expansion} is about expanding tokens, including the manipulation of expansion order and the suppressing of expansion.

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21
votes
1answer
143 views

Is implicit `\relax` in conditionals explained anywhere in the TeXbook?

I have been relying for years on TeX's behavior where, say \if1\fi expands to nothing and \if1\else\fi does the same. In the second case TeX inserts an 'implicit' \relax when it tries to expand \else. ...
24
votes
3answers
442 views

Why the \expandafter\@firstoftwo idiom?

I see a lot of macros which are conditional tests followed by a {true}{false} pair defined so that they result in either: \expandafter\@firstoftwo or \expandafter\@secondoftwo Why are these \...
8
votes
1answer
273 views

Expandable, standard TeX only way to compare balanced token lists

Is there a (reasonably) efficient macro that does something similar to \long\def\comparets#1#2{\def\aa{#1}\def\bb{#2}\ifx\aa\bb true\else false\fi} except is expandable (i.e. \newcomparets{<...
4
votes
1answer
160 views

Expand macro into xparse \SplitList macro

I had help making a macro to process a list of arguments separated by ; into an itemize environment. To achieve this, xparse was used. When I tried to wrap the lists of arguments in a macro, nothing ...
6
votes
4answers
963 views

How to fill a dynamically generated table with dynamic content?

how do I generate a tabular dynamically while filling it with dynamic data? Example: Let's say I have \def\N{10} and I want to generate a table with \N columns, where the top cell of each column ...
8
votes
4answers
236 views

Problem with csname macro expansion

I want to dynamically define some macros that essentially create a list of \refs. I seem to be able to define these macros but then I am unable to print them. Here is my M(non)WE: \documentclass{...
5
votes
1answer
36 views

Selectively apply \global to some tokens set via an \input file

This should be simple, but I can't quite guess the correct combination of \expandafter needed. The value of \MyTokenGlobal should not be changed via the \input, but the value of \MyTokenLocal should ...
7
votes
1answer
113 views

Expand macro at float typesetting (not at definition) time

To my knowledge, the contents of a float environment are put into a box when the float is defined. Is it possible to proccess a user defined command/macro when the float is actually typeset, e.g. to ...
37
votes
4answers
2k views

How does your mind bend \expandafter to its will?

Expansion is often cited as one of the most arcane aspects of TeX, more akin to witchcraft than to something easily picked up by the newcomer. There are many great questions and great answers about ...
11
votes
2answers
473 views

Save counter value inside command?

I'm trying to automatically generate commands based on the value of a counter: \documentclass{article} \newcounter{count} \newcommand\generator[1]% {% \stepcounter{count}% \expandafter\def\...
2
votes
1answer
238 views

Macro for pgfplot cycle list entry

I'm trying to define multiple cycle lists based on macro variables. The reason for this is that I need more than one list and I want to be able to change the appearance quickly while keeping the ...
1
vote
1answer
211 views

Check the value of a pgfkey

I need to be able to check if the value of a pgfkey is empty or not. A solution I have tried (using package etoolbox): \edef\temp{\pgfkeysvalueof{/path/key}}% \expandafter\ifstrequal\expandafter{\...
4
votes
1answer
126 views

Changing the default value of a pgfkey

I want to create a command that can change the default value of my pgfkeys. I think the problem is that the value set as default is not expanded. Therefore the icondefaultsa below doesn't work. ...
10
votes
3answers
430 views

Write on a file and input it

I'm trying to redefine a \tableofcontents-like command. I proceed this way : the displayed elements are written to a file, and the file is input when I want the display. If I know the toc will be ...
2
votes
1answer
107 views

Expanding beamer arguments

I have created a new command that takes beamer-arguments (<...>), but I'm not able to pass them on. I suppose it's a \expandafter problem. Does anyone have a clue? \documentclass{beamer} \...
4
votes
1answer
199 views

Passing variable as argument

I need to pass a variable to a command, but I cannot get it to work. Here is a short example that shows that #1 can be sent to a command, but not a variable that is a copy of #1. Why is this? \...
7
votes
1answer
127 views

Make the pattern of a \def depend on another macro

I would like to set up a macro defined something like this: \def\processline string: #1.#2\relax{\gdef\errorline{#1}} The catch is that the string should be given by the contents of another macro. ...
15
votes
1answer
308 views

A problem with counters

While trying to answer a question I came upon a problem with counters and I need some help. The idea is to collect answers to some numbered exercises, so the collected answers can be all typeset at ...
8
votes
1answer
288 views

Prevent \caption from expanding argument too early

I have a macro that defines some internal macros and does so locally as to not clutter the global namespace. However, \caption seems to expand the macro's argument too early. Here is a minimal example....
17
votes
2answers
412 views

Why does this simple \ifx test fail?

This should be easy, but I don't understand why the test below fails... I expected Hurrah! to be printed when the \currentchar count reaches 90 (i.e. the character code of Z). There must be some ...
7
votes
1answer
116 views

Expand package option, to make contained character math-active

In an answer to another question of mine, egreg posted code, which activates a character in math mode and gives it the function of \operatorname. Now I want to put this into a package and set the ...
8
votes
2answers
620 views

Expanding a sequence inside a TikZ path

I am trying to draw a simple path using TikZ, with a custom syntax to specify it. This works: \documentclass{article} \usepackage{tikz} \begin{document} \newcommand{\latticepath}[1]{ \draw[thick]...
4
votes
1answer
248 views

Is it possible to define abbreviations for coding?

I am using the tikz-timing package to create a timeline since chronosys and chronology wouldn't cooperate and were too limited and archaic-looking to suit my purposes, and moderntimeline unfortunately ...
9
votes
2answers
817 views

\g@addto@macro appending code using parameter

After a lot of trial and error, I haven't been able to solve the following problem: A simplified version: I want to use \g@addto@macro to add code to another macro wich will use a command of the macro,...
8
votes
2answers
454 views

Expanding all arguments of a command before appending it to another macro

\documentclass{article} \makeatletter \usepackage{ltxcmds} \newcounter{mycounter} \setcounter{mycounter}{7} \newcommand{\mysndc}[3]{#1 #2 #3} \newcommand{\mycommand}{} \newcommand{\mytrdc}[1]{\ltx@...
9
votes
2answers
350 views

How does this answer work?

Harald Hanche-Olsen posted some interesting code in answer to this question. Could someone explain how it works? I understand (I think) the futurelet and the expansions. I don't understand: Where ...
4
votes
1answer
183 views

How to expandafter an environment?

I have the following problem: I want to create a beamer presentation and introduced a new environment using xparse. The environment has one optional argument (+ two mandatory). Now I want to create an ...
4
votes
2answers
646 views

Concatenate macro with string

I try to expand a macro containing a string with another string. It is in the document and thus I want to avoid using @. I tried the following using etoolbox \expandafter\def\fileAcronym\...
8
votes
1answer
106 views

How can I expand macros and write the expansion to an external file?

I'm trying to do a bit of single-sourcing with my resume, and would like to write given information to an external text file. \documentclass{article} \usepackage{expl3,xparse} \ExplSyntaxOn \...
4
votes
1answer
60 views

Expl3 prop doesn't seem to work when the key is a macro value

I'd expect this example code to give two identical lines, however \usevalue{\xyz} doesn't result in XYZ as the other. Can I force the key to be expanded to make \usevalue{\xyz} and \usevalue{0} refer ...
6
votes
1answer
214 views

Macro expanding to comma separated list

I'm trying to use a macro for pgfplotstable labels but the macro is treated as a single entry of a csl rather than a csl. The Question asked in Using a macro as value of addtotoc in \includepdf ...
5
votes
1answer
313 views

\begingroup, \endgroup expansion problem “Undefined control sequence.”

I just created an answer that uses a temporary variable with \write\@auxout and thought it would be good idea to scope with \begingroup, \endgroup. For some Reason this results in: ! Undefined ...
1
vote
0answers
35 views

What's the shortest input that makes TeX and/or TeX-based systems go into a loop? [duplicate]

The following 12-character input causes TeX to go into a loop. \def\x{\x}\x It won't crash, it won't produce an error message, it'll just sit there for ever, trying to compile the document (but not ...
1
vote
0answers
83 views

About those magic primitives [closed]

While learning TeX, I found some primitives are magic (e.g., \expandafter \futurelet \aftergroup). These primitives can change the expansion order of the input stream. Have anyone made any ...
5
votes
2answers
136 views

Comparing the arguments passed to a macro

I want to write a command which makes a norm of a vector, with following syntax: \xnorm{v}. I want the norm delimiters to adapt to the size of the expression contained in \xnorm{}, BUT I want also an ...
6
votes
3answers
453 views

How can I get these two nested \foreach loops to work?

I try to use nested \foreach loops to create edges between many nodes. \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} \node (a) at (0, 1) {}; \node (b) at (0, -...
5
votes
2answers
1k views

How to get character code defined with \let (! Improper alphabetic constant)

Here's a example with the "! Improper alphabetic constant" error: %% this is ok \newcount\mychar \mychar=\number`a\relax \showthe a % shows You can't use `the letter a' after \the \showthe\...
6
votes
1answer
109 views

Expanding a macro as many times as possible without error

I'd like compute cosets using the permute package. Here's what I have so far: \documentclass{article} \usepackage{expl3,xparse,permute} \ExplSyntaxOn % Create a new command to compute the right ...
5
votes
1answer
150 views

Using xstring macros in edef

I've tried to use \protect to make the following \edef work but no luck. Can it be done somehow? \documentclass{article} \usepackage{xstring} \begin{document} \def\abc{a,b,c} \edef\result{\...
8
votes
1answer
96 views

Moving the optional argument

When I create macros using \newcommand, I usually provide default variants setting some of the first arguments in a sort of partial application style \newcommand\five[5]{#1,#2,#3,#4,#5} \newcommand\...
7
votes
1answer
70 views

expl3: \tl_put_right:Nx chokes on \{

I am trying to compose a command into a token list. \documentclass{article} \usepackage{expl3} \begin{document} \ExplSyntaxOn \tl_new:N \__a \tl_new:N \__b \tl_new:N \__c \tl_set:Nn \__a { ...
10
votes
1answer
67 views

Reading (input) a file whose name is created with a label

I don't want to get into the details of why I want to do this, but I would like to: create a new counter called filenumber; create a file whose filename is \jobname\thefilenumber.txt and write to it;...
0
votes
0answers
30 views

“Expanding” locally defined commands [duplicate]

I wrote a paper using custom ("locally defined") commands and environments (e.g. a new quote environment, loads of abbreviations, etc.). The journal requires me eliminate all non-standard LaTeX ...
44
votes
6answers
7k views

LaTeX macro expander

Is it possible to have LaTeX (or another program) to expand a the macros in a .tex file, and output the expanded LaTeX source? If no such program exists: are LaTeX macros processed simply as string ...
4
votes
1answer
131 views

Expanding a variable within a protected label

I have some trouble with expanding variables within a protected label. I need a automatisated caption with a label all inside a command. Within the caption I want to have a two digit number (padzeroes)...
5
votes
2answers
178 views

Creating a new array column type dynamically

I am evaluating toks registers for various uses - they are still fairly new to me. I'm using them to construct a table column-wise. During this, I have come across an issue I have failed to find a ...
4
votes
1answer
112 views

Using complicated macro in \thanks command of abstract package

The \saythanks command chokes when \thanks has been called with a macro that takes (and executes!) another macro as argument: \documentclass[twocolumn,a5paper]{paper} \usepackage{abstract} \...
11
votes
1answer
125 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 ...
4
votes
1answer
129 views

Can I expand a macro argument once without using a scratch register?

I'm still trying to get my head around how expansion works in TeX. One thing I can't figure out is how to expand a macro argument once without having to use a scratch register as an intermediate. As ...
3
votes
1answer
113 views

Differentiate reference based on type (problem with argument expansion)

Since I use unnumbered sections, I'd like to have a variation of \autoref that uses names instead of numbers in the case of sectioning, but keeps its usual behaviour for other environments. I've come ...