Latex Modes For Conditional Text Inclusion

What is Conditional Text Inclusion?

Conditional text inclusion refers to the capacity in LaTeX to flexibly include or exclude blocks of text based on evaluated conditions. Commands like \ifdef check if a control sequence is defined, and show or hide text depending on the result. This allows a LaTeX document to adapt its content based on logical tests.

Use cases for conditional text inclusion include:

• Creating multiple document variants from a single source file depending on build configuration
• Marking optional content passages that can be turned on or off
• Altering the document for different output formats like screen, print or PDF
• Making redactions in legal or secured documents
• Producing both complete and concise versions without file doubling

So in essence, conditional text inclusion enables efficient and flexible document preparation. The author can resolve upfront which variability points are required, and markup conditionals to generate the required outputs from a single codebase.

Using \ifdef to Include Text Conditionally

The \ifdef command checks if a specified control sequence is currently defined. Its syntax is:

\ifdef{control sequence}  
Text to include if defined
\else  
Text to include otherwise  
\fi

For instance, we can set up a conditional include for the draft status:

\newif\ifdraft
\drafttrue

\ifdef{\ifdraft} 
This is draft copy only
\else
This is final released copy  
\fi

Here \drafttrue sets up \ifdraft as defined. So the \ifdef evaluates to true on its test, and shows the "draft copy" text.

We turned definitions on or off to control conditional includes. Say we change to \draftfalse before the test. Then \ifdef{\ifdraft} would evaluate false instead, excluding the "draft copy" block.\p>

Any control sequence can stand in for \ifdraft here - this technique works the same for user-set toggles. And multiple conditional tests can show or hide differing text as needed.

Other Conditional Commands: \ifnum, \ifdim, etc.

LaTeX offers several low level conditionals to check values directly:

• \ifnum compares two Arabic numbers
• \ifdim checks relationship between two dimensions
• \ifthenelse constructs full if-then-else test
• \boolean runs test on a Boolean true/false value

For instance, we may render text depending on page count:

\newcounter{pagecount} 
\setcounter{pagecount}{16}

\ifnum\value{pagecount}<20  
This is a short document
\else
This is a long document
\fi

Here \ifnum compares the page counter to 20. So the "short document" text renders since 16 is less than 20.

Logical Operators: \AND, \OR, \NOT

Tests can be logically combined using operators like:

• \AND - True if both parts true
• \OR - True if either part true
• \NOT - Inverts true/false state

For example:

\newif\ifshort\shorttrue
\newif\ifdraft\drafttrue

\ifdraft \AND \ifshort
 This is draft short version
\else
 This is final full version
\fi 

Here both \ifshort and \ifdraft are true. \AND requires both sides true to pass. So the "draft short" text renders. If either was false, main text renders instead.

Any mix of tests can be logically strung together like this. \OR would show the text if either condition passes, while \NOT\ifshort would check specifically for "not short".

Use Cases for Conditional Text

Typical use cases for conditional text include:

1. Multiple document variants - Single source can produce short, long, draft, complete versions depending on conditionals
2. Build configuration - Toggle conditionals to mark debug, release, publication candidate builds
3. Temporary content - Include incomplete sections marked with conditionals
4. Format reflowing - Wrap text blocks for screen, print, PDF outputs
5. Redaction control - Sensitive content included but excluded for public documents

Proper use keeps conditionals focused on building variants of the same base document. Don't overly fragment logical text units across too many includes. And minimize redundancy between branches.

Common misuses like maintaining entirely separate documents via includes increases complexity and hurts maintainability.

Example Document with Conditional Text

Here is an excerpt LaTeX document using conditional text elements:

\documentclass{article}
\newif\iflongversion\longversiontrue
\newif\ifSensitivityCheckOK\SensitivityCheckOKtrue
 
\begin{document}

\title{Sample Document}
\author{Anon Ymous}
 
\maketitle

\section{Introduction}
Some introductory text here. The document 
\ifdef{\iflongversion}
provides background details on the core topic areas. We elaborate the key challenges around containment mechanisms.
\endif 

\section{Key Topic Areas}

We examine several main areas:

\begin{itemize}  
\item Transport protocols
\item Rights delegation 
\item Verification scopes \ifdef{\ifSensitivityCheckOK} including redaction standards \fi 
\end{itemize}
 
\section{Conclusions}
Some concluding remarks are given. \ifdef{\iflongversion} Additional work remains to address open question around redacted access patterns. \endif 

\end{document} 

Here conditional excludes provide both short form and extended content. The \ifdef {\SensitivityCheckOK} line demonstratesKIN conditional redaction for sensitive information. Only present if approved for inclusion via \SensitivityCheckOK flag.

By toggling the \iflongversion and \SensitivityCheckOK switches, we can produce varying document forms from same source: concise or extended, redacted or complete.

Conclusion

LaTeX's conditional text inclusion capability allows efficient document variability. Core commands like \ifdef, alongside other conditionals and logical operators give extensive control over includes and excludes.

Typical applications target multiple outputs from single source. But misuse via over-fragmentation can increase complexity. Best practices focus conditionals mainly around high-level build variants.

For more on conditional text techniques, refer to "Best Practices for Document Engineering" (LaTeX Press 2023). Appendix C covers recommended conventions given project scope.