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

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31
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2answers
958 views

Why do we need eleven expandafters to expand four tokens in the right order?

In Appendix D - Dirty Tricks Knuth gives an example of expanding four tokens in the right order by using eleven \expandafter commands. Here, is the code slightly adapted for to-morrow! \tracingmacros=...
15
votes
4answers
729 views

Expandable full expansion of tokens that preserves catcodes

Is it possible to fully expand tokens in an expandable manner and preserves category codes? I'd like to do this just using pdfTeX. I'm looking for something that would work like this: \def\foo{foo} \...
3
votes
2answers
532 views

Expand directory names using nested macro definitions

Background Would like to use values from macros that reference other macros (n-levels deep) and apply their values to the \path command. Problem (Scenario A) The following works: \usepackage{url} ...
7
votes
2answers
749 views

Using \nameref within \path

Background Looking to apply a consistent style to file and directory names. The book's appendix has a subsection for every file referenced by the book. Every subsection has a label whose value is ...
15
votes
2answers
2k views

How to add a hook to a macro

LaTeX uses hooks extensively, one method employed is the command g@addto@macro. It is defined in source2e as: \long\def\g@addto@macro#1#2{% \begingroup \toks@\expandafter{#1#2}% \xdef#1{\...
8
votes
2answers
2k views

Building labels out of counters

There is a simple version to my question, and a complex version. First, the simple version: I want to generate label names by combining a constant string with a counter's value, something like what is ...
22
votes
2answers
965 views

Stripping the pt from a dimension

LaTeX defines in ltfssbas.dtx a macro called \strip@pt (at line [246]) which strips the pt part from a dimension returned by \the\dimension. The definition is shown as a minimal working example below: ...
9
votes
2answers
351 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 ...
19
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2answers
1k views

Minimal \protected@edef example

I recently came across \protected@edef in the/a LaTeX2e source. Can anyone give me a minimal or simple example, where I need this? I know this has to do with fragile commands/robustness, but I am ...
190
votes
3answers
14k views

What is the difference between Fragile and Robust commands?

So I've read a few times about this, the “moving arguments” and all that. But what does it really mean? Could someone explain in a few words what is going on at the TeX level, what is the difference ...
16
votes
1answer
507 views

How do I ‘expand’ a control sequence `\let` to a character?

Consider the following: \let\1=X \edef\2{\1} \show\1 \show\2 The result is > \1=the letter X. > \2=macro: ->\1. Is it possible to ‘expand’ the meaning of \1 so that \2 contains just X?...
11
votes
4answers
709 views

What's the best/right way to test an argument to a macro?

This is essentially asking how to do a case switch in LaTeX. I want to define a macro so that if the argument passed is one thing, then something happens, and if not then something else happens. I ...
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 ...
21
votes
1answer
702 views

Why do the definitions of \quad, etc. have \relax in them?

Plain Tex defines \quad so: \def\quad{\hskip1em\relax} Why is the \relax there? It's usually used as a token that can't be expanded, serving as a "do nothing" operation after macro expansion is ...
8
votes
6answers
467 views

Is it possible to define a command that can be used where literal <comma-separated-list> is normally required?

I suspect I'm asking for magic, but I'll go ahead anyway. Suppose I have a command that accepts an arbitrary-sized list of comma-separated terms. One that we're all familiar with is \usepackage ...
127
votes
4answers
27k views

When to use \edef, \noexpand, and \expandafter?

I'm quite happy hacking TeX macros and cobbling together bits and pieces from different style files to suit my own ends, but I have a suspicion that my resulting hacks are not quite as elegant as they ...
4
votes
2answers
242 views

Can super/sub-scripts bind more tightly than macro expansion?

By "bind more tightly" I refer to the order in which operations are carried out by default. Experimenting shows that if \ab is ab and \cd is cd then \ab^\cd is ab^cd. I would like it to be {ab}^{...
10
votes
6answers
736 views

Is there a '\ReallyDontExpandUntilTheLastMinute' command?

There's a couple of things I want to be able to do that are quite similar and basically involve keeping back a macro expansion until the last minute. Possibly the simplest example is that I have a ...