LaTeX Conditional Statements

Conditional statements in LaTeX allow you to create dynamic documents that adapt based on specific conditions. These powerful tools enable you to control the content and formatting of your document programmatically.

Basic Syntax

LaTeX provides several commands for implementing conditional logic:

• \ifthenelse: For complex conditions
• \ifnum: For numerical comparisons
• \ifodd: To check if a number is odd
• \ifx: To compare two commands or macros

The \ifthenelse Command

The \ifthenelse command is the most versatile and commonly used conditional statement in LaTeX. It requires the ifthen package.

\usepackage{ifthen}

\ifthenelse{condition}{true-text}{false-text}
    

Here's a practical example:

\newcommand{\displaygrade}[1]{
    \ifthenelse{\equal{#1}{A}}{Excellent performance!}{
        \ifthenelse{\equal{#1}{B}}{Good job!}{
            \ifthenelse{\equal{#1}{C}}{Average performance.}{
                \ifthenelse{\equal{#1}{D}}{Needs improvement.}{
                    Failed.
                }
            }
        }
    }
}

\displaygrade{B}  % Output: Good job!
    

Numerical Comparisons with \ifnum

For comparing numerical values, the \ifnum command is more efficient:

\newcounter{score}
\setcounter{score}{85}

\ifnum\value{score}>90
    Excellent score!
\else
    \ifnum\value{score}>80
        Good score.
    \else
        \ifnum\value{score}>70
            Average score.
        \else
            Needs improvement.
        \fi
    \fi
\fi
    

Boolean Expressions

LaTeX supports boolean expressions for more complex conditions:

• \and: Logical AND
• \or: Logical OR
• \not: Logical NOT

Example using boolean expressions:

\newcommand{\checkeligibility}[2]{
    \ifthenelse{\(\not\equal{#1}{}\) \and \(#2 > 18\)}{
        Eligible
    }{
        Not eligible
    }
}

\checkeligibility{John}{20}  % Output: Eligible
\checkeligibility{}{17}      % Output: Not eligible
    

Best Practices

• Use \newif for creating custom boolean variables
• Nest conditions carefully to maintain readability
• Consider using LaTeX packages like etoolbox for advanced conditional operations
• Test your conditional statements thoroughly to ensure correct behavior

Related Concepts

To further enhance your LaTeX documents, explore these related topics:

• LaTeX Loops for repetitive tasks
• LaTeX Custom Commands to create reusable code
• LaTeX Error Handling for robust document compilation

By mastering conditional statements, you'll be able to create more dynamic and responsive LaTeX documents, adapting to various scenarios and user inputs.