{conditionals} is about macros like \if and \ifx that may execute other macros depending on whether certain conditions are true or not. Popular packages are {etoolbox} and {ifthen}.

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23
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What is an \if?

I'm reading TeX by Topic, but in little chunks (rather than from first page to last) and just read the stuff on conditionals. I want to be sure that I understand what's going on when TeX starts ...
15
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4answers
2k views

Making switch/case with etoolbox's \ifdefequal

I've got a define such as \def\doctype{SomeString}. \doctype can take on one of five values. I want to do something like a switch statement in a programming language, i.e. (pseudocode): switch ...
11
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2answers
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Conditional cases expression

How can I create a command \if with 1 argument, namely #1, \if{#1=1}{symbol1}...{#1=n}{symboln} that returns symbol1, when #1 is 1, ..., and returns symboln, when #1 is n, and returns nothing, ...
17
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2answers
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What does \begingroup\expandafter…\endgroup do?

I often see code of the following form in package implementations (this example is from the LaTeX3 sources): \begingroup\expandafter\expandafter\expandafter\endgroup \expandafter\ifx\csname ...
28
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2answers
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Understanding \@ifnextchar

I understand the definitions of the \makeatletter and \makeatother commands and also \def and \newcommand somewhat. But, explained in a simple way, what is happening in the following line? ...
22
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4answers
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On testing two fully expanded character strings for equality

I know three macros that test two fully expanded character strings for equality: \ifthenelse{\equal{<op1>}{<op2>}}{<true>}{<false>} (ifthen package) ...
17
votes
6answers
1k views

Checking if a number is a multiple of 4

Using etoolbox, ifthen, or another form of conditional checking, how can I check if a value is a multiple of 4? E.g. if the number is 4, 8, 12, 16, etc., then it returns "true".
15
votes
3answers
1k views

Includegraphics maximum width

With \includegraphics I can give the width of the resulting image (which would be scaled). How can I give a maximum width of the image? That is, if the original is smaller than X, I'd like to keep ...
13
votes
4answers
226 views

How do you test whether a known key value has been set in pgfkeys

Using the .code handler to my keys and a private macro, I can easily test whether a key has been set when using pgfkeys. For example: \documentclass{article} \newcounter{mytestenvcounter} ...
12
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2answers
925 views

Doing something only when the draft option is on?

I would like to do some stuff that is only enabled when the draft option is given in \documentclass[draft]{article}. How would I go about doing this?
12
votes
2answers
745 views

How do I conditionally execute something based on a documentclass option?

I'd like to conditionally do some things (like input a file) depending on if a specific class option was passed. For example, I'd like to have an "instructor" option to the class that would input a ...
11
votes
2answers
357 views

How to detect if option provided via \tikzset

I would like to be able to detect if a particular option has been provided via a \tikzset and issue a message based on that. The MWE yields: But once the conditional works (just a comment for ...
5
votes
3answers
866 views

How to use the exact same file for handout and presentation modes in beamer

I want to use the exact same file for my beamer presentation and handout. I do not like the need to comment out lines in order to create the handout or presentation (my current solution), nor do I ...
13
votes
3answers
431 views

Detect which text “mode” (normal, italic, bold, etc.) is currently in use?

In my document, I'm often setting upper case words and abbreviations in small caps because it avoids breaking the flow (which upper case words does). Also, many words (like CUDA, for instance) are ...
11
votes
2answers
243 views

String comparison in \ifthenelse

I want find a certain line of text in a data file cities.txt: A;London B;Berlin C;Paris with the xstring and [xifthen][2] packages: \documentclass[12pt, a4paper]{article} \usepackage{xstring} ...
10
votes
5answers
780 views

Teach me how to use \loop…\repeat constructs, etc

The following code snippet is a part of the solution given here: \def\IncludeOutput#1{ \parskip=2mm \def\examplename{#1} \pdfximage{\Directory/\examplename.pdf}% ...
10
votes
3answers
738 views

Choosing styles conditionally in TikZ

I want to create a series of images that visualise a recursion tree as walked on by an algorithm. That means that different styles are applied to nodes depending on the step the algorithm is in, such ...
8
votes
2answers
331 views

Custom ToC — Put vspace only below chapters that have sections in them

I’m using the titletoc package in the book class. Currently, my chapter entries are configured like this (I left out the unimportant parameters for simplicity): \titlecontents{chapter}[0pc] ...
4
votes
3answers
500 views

Create odd-numbered answers, or all answers

I'm starting with a clean slate creating a solutions manual. I would like the ability, by setting a switch, to produce only the solutions for the odd-numbered problems, or those for all problems, in ...
22
votes
6answers
3k views

What is \iffalse for?

So this is something I've wondered about for a while. What use is a conditional that always evaluates to false? I guess it's a neat way to "hide code from LaTeX" but apart from that, is it ever ...
21
votes
2answers
331 views

Show footnotes on odd pages only

I'm writing my thesis using the scrbook-class. Is it possible to display footnotes only on the odd (right) pages? This should mean that \footnote{something} should be collected on even pages and ...
16
votes
2answers
862 views

Difference between \newbool and \newtoggle from etoolbox package

Paul Gaborit's answer to How to detect if option provided via \tikzset uses \newbool to define a new boolean \booltrue to set a boolean, and \ifbool to perform a conditional operation all from ...
13
votes
1answer
2k views

Can I test if a file exists? [duplicate]

Can I somehow test if a file exists? And can I use this to do only things when it exists? I like to do something like if(exist('members.csv')) { do something }
12
votes
2answers
622 views

Automatically remove page number if document has only one page (but not if two)

I write a lot of documents (agreements) based on memoir with the article option. Normal pagestyleis plain (page number centered in the footer). Sometimes a document is only one page long, and a page ...
12
votes
1answer
704 views

How to determine whether a list of figures is empty?

I want to check whether the document has any figures so as to decide whether or not to have a list of figures. Is this possible? Feasible without doing something like parsing the lof file? Note that ...
11
votes
4answers
1k views

How to make a “condition” in a macro?

I would like to make a macro with two parameters which return a text. For instance, I want \M{1}{5} to return [1,5], and \M{2}{2} to return [2] (because the two arguments are the same). So I need to ...
10
votes
1answer
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Comparing an argument to a string when argument is a result of a command with etoolbox

I've got an example like that: \documentclass{article} \usepackage{etoolbox} \newcommand{\ab}{a} \newcommand{\aORb}[1]{% \ifstrequal{#1}{a}{"a" was given}{not a}, % ...
9
votes
1answer
472 views

Hiding section titles when the section is empty

I have created a macro like this: \newcommand{\showsection}[2]{ \ifstrequal{#2}{}{}{\section{#1} #2} } It should be used like this in the document: \showsection{Books}{ Do you know any ...
9
votes
2answers
452 views

biblatex: is there a command analogous to \ifciteseen but within one page?

Biblatex is loaded as \usepackage[style=numeric-comp,hyperref=true]{biblatex} \ExecuteBibliographyOptions{citetracker=true,sorting=none,firstinits=true} I am looking for an if-command, which would ...
8
votes
1answer
2k views

Using ifthenelse in pgfmath

Following questions on constructing functions on the forum, I tried to build some myself. I can't seem to get the ifthenelse function in TikZ/PGF to work. Here is an example: ...
7
votes
1answer
681 views

Conditional compilation of beamer slides

I'm preparing a beamer slideshow, and I will have to print slides. I would rather use landscape mode slides, but it is possible that I need to use portrait mode ones. Sadly, I won't know until a few ...
6
votes
4answers
261 views

How to detect and condition based on hostname

How do I construct a conditional statement based on the hostname of the compiling computer in LaTeX? For example: \ifhostname{mymachine} \dostuff \else \dootherstuff \fi Why: I am working with ...
4
votes
2answers
412 views

How to configure theorems depending on the document class?

I would like to have \newtheorem{teo}{Teorema}[chapter] if the book class is loaded but \newtheorem{teo}{Teorema}[section] if the article class is loaded. Can I do this with some sort of ...
16
votes
3answers
3k views

What is the difference between \ifx\somecommand\undefined and \ifdefined\somecommand\else?

What is the difference between \ifx\cyrdash\undefined and \ifdefined\cyrdash\else? \cyrdash is any macro.
12
votes
2answers
415 views

How to tell when to use pdflatex, latex, and xelatex for any given tex file?

I'm writing an automatic compiling pipeline that should be able to compile any given tex file into a pdf. The diversity of the input tex files mainly shows up in what format of figures they use and ...
9
votes
3answers
661 views

How to implement a command that checks for loaded packages?

I use the following code to check if a package is loaded: \RequirePackage{ltxcmds} \newcommand{\IfPackageLoaded}[2]{\ltx@ifpackageloaded{#1}{#2}{}} However, sometimes I want to check if more than ...
9
votes
2answers
213 views

Is it possible to abort loading a package if it's too old?

I'm working on a package that has to work on both TeXlive 2009 (Ubuntu, so updating TeXlive is a nonstarter) and later versions, and I'd like to be able to use fontspec with LuaLaTeX if we're on ...
8
votes
1answer
367 views

How do I make make different versions of my document with command line compile flags?

I've found a number of answers online, and plainly none of them have seemed to be able to execute any conditional code. This answer looked particularly promising. One thing I noticed is that in the ...
7
votes
1answer
1k views

How to tell if the current section is defined in Beamer?

I am customising the footer of my Beamer slides. The footer displays the title of the slides, followed by a ":", and then the current section title. This works fine if the current section is defined. ...
6
votes
2answers
92 views

Separators for author group (IF conditon)

I am new to LaTeX, just a beginner, basically a Perl developer. I have created a LaTeX file \begin{document} \cont{\iname{\isurname{Name1}\ifname{K. C. G.}}\iname{\isurname{Name11}\ifname{Y. ...
6
votes
2answers
148 views

Is “conditionals” name of package?

In some package I have seen construct like this one: \if\blank{\myMacro}% %do something \else %do something else \fi I like it and I want to use it to test if call to a macro has empty result. ...
5
votes
1answer
257 views

Suppressing remarks when not needed

I have written some remarks in some of my works that are somewhat informal and repetitive in nature (mainly for my own clarification). I was wondering if there is a way of suppressing them when I ...
4
votes
1answer
128 views

How to create two PDFoutput from the same source

I have a very long source file. I would like to prepare from this source two PDF files: PDF contains all of the source file PDF containing only a few, marked earlier parts of the source file. How ...
4
votes
2answers
102 views

How to test if a given reference belongs to a list of labels?

This question is a prolongation of my previous question How to choose from a list for using result in \ref?. I got really good and interesting answers. Unfortunately I can not implement them for my ...
1
vote
2answers
236 views

How to multiply compile according to selected tags?

I would like to do the following, by I am not sure how. Say I have a LaTeX file with series of annotations, each with zero or more "tags" (say, about their contents or the project they are related ...
25
votes
4answers
5k views

How to conditionally define a new command in LaTeX?

I'm trying to compile a LaTeX code with an older version of some package. Thus, I'm having a few issues due to undefined commands. How can I add conditional code so that I can define some work-around ...
19
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1answer
9k views

Conditionally hidden slides in beamer

When creating a presentation, I sometimes create extra slides that contain additional information, a more thorough explanation, or an extra plot pertaining to certain parts of my talk. These extra ...
24
votes
3answers
6k views

When to use @ in an \if statement

I am new to LaTeX and so this question might come across as rather basic. It might also reflect my biases/assumptions from my C/C++ programming days. I was seeing the code of the 'exam' class and ...
18
votes
1answer
228 views

Is something the first item on a page?

How can i identify logically, whether something is the first item on a page, i.e. there is nothing above it (apart from header)? Consider the following, is is basically a feature environment, which ...
18
votes
7answers
599 views

How to define a command to feed the contents of a list into an \ifcase construct?

It's common to use an \ifcase construct to redefine a command depending on the value of a counter. The following example illustrates this: \documentclass{article} \usepackage{xcolor} ...