common-packages-tips

Common Packages and Tips

The previous chapters have already used quite a few packages; this chapter provides a systematic wrap-up: package quick reference, custom commands, code listings, multi-file projects, latexmk, and troubleshooting mindset. Mastering these "toolbox" topics evolves you from someone who can write LaTeX to someone who can manage LaTeX projects.

Common Package Quick Reference

Packages are loaded with \usepackage[options]{package-name}, all placed in the preamble.

Package	Purpose	Appeared In
geometry	Page margins and paper	LaTeX Document Structure and Layout
fancyhdr	Headers and footers	LaTeX Document Structure and Layout
amsmath / amssymb	Math formula enhancement / extended symbols	LaTeX Math Formula Basics, LaTeX Advanced Math Formulas
graphicx	Graphics	LaTeX Figures and Tables
booktabs / multirow	Three-line tables / vertical cell merging	LaTeX Figures and Tables
enumitem	List customization	LaTeX Text Formatting and Lists
xcolor	Color definitions	Introduced in this chapter
listings	Code listings	Introduced in this chapter
hyperref	Hyperlinks and bookmarks	LaTeX Cross-references and Bibliography Management
biblatex	Bibliography (modern solution)	LaTeX Cross-references and Bibliography Management
float	Forced figure/table positioning [H]	LaTeX Figures and Tables

When the local environment prompts File 'xxx.sty' not found, install it with tlmgr install xxx (TeX Live); MiKTeX will download automatically. Overleaf comes with almost all packages, so no such trouble.

Custom Commands: \newcommand

When you write the same content more than three times, it is time to define a command. \newcommand{command-name}[arg-count][definition].

Example: Three Types of Custom Commands

% No argument: shorten a long command
\newcommand{\R}{\mathbb{R}}        % Writing $\R$ now produces $\mathbb{R}$

% One argument: encapsulate a fixed format
\newcommand{\email}[1]{\texttt{#1}} % #1 denotes the first argument

% Optional argument with default value: [arg-count][default]
\newcommand{\vecn}[2][n]{x_1, \dots, x_{#1}}
% Usage: $\vecn$ produces $x_1,\dots,x_n$
%       $\vecn[5]$ produces $x_1,\dots,x_5$

\begin{document}
A function defined on $\R$, vectors $\vecn$ and $\vecn[5]$.
Contact email \email{uniresearch@email.uniplore.com}.
\end{document}

A function defined on $\mathbb{R}$, vectors $x_1, \dots, x_n$ and $x_1, \dots, x_5$.

Contact email: uniresearch@email.uniplore.com.

Command	Purpose	Note
\newcommand	Define a new command	Command name must not conflict with existing commands
\renewcommand	Redefine an existing command	Use when customizing default styles; modify basic commands with care
\newenvironment	Define a new environment	Same syntax; provide start and end code

Get to know the syntax for custom environments as well:

Example: Custom "Note" Environment

\newenvironment{note}
{\par\medskip\noindent\textbf{Note:}\itshape} % Start code
{\par\medskip}                                 % End code

\begin{note}
This content will automatically start with "Note:" and be set in italics.
\end{note}

Note: This content will automatically start with "Note:" and be set in italics.

Code Listings: The listings Package

For posting code in technical documents, use the listings package. Language highlighting, line numbers, and borders are all automatic.

Example: Code Block with Highlighting and Line Numbers

\documentclass{ctexart}
\usepackage{listings}         % Code listing package
\usepackage{xcolor}           % Color support

\lstset{                      % Global code style settings
basicstyle=\ttfamily\small, % Monospace font, slightly smaller size
keywordstyle=\color{blue},  % Keywords blue
commentstyle=\color{gray},  % Comments gray
stringstyle=\color{purple}, % Strings purple
numbers=left,               % Line numbers on the left
numberstyle=\tiny\color{gray},
showstringspaces=false,     % Do not show space markers inside strings
frame=single                % Single-line frame
}

\begin{document}

\begin{lstlisting}[language=Python, caption=Computing the Fibonacci Sequence]
# Compute the n-th Fibonacci number (Chinese comment test)
def fib(n):
if n < 2:
  return n
return fib(n - 1) + fib(n - 2)

print(fib(10)) # Output 55
\end{lstlisting}

\end{document}

Listing 1: Computing the Fibonacci Sequence

# Compute the n-th Fibonacci number (Chinese comment test)
def fib(n):
  if n < 2:
    return n
  return fib(n - 1) + fib(n - 2)

print(fib(10)) # Output 55

lstlisting is a "verbatim environment": internal content is not interpreted by LaTeX at all; &, %, etc. do not need escaping. caption is also automatically numbered (Listing 1). Common language names include Python, C, Java, HTML, SQL, bash, etc.; without specifying language, plain text coloring is used.

UTF-8 Chinese support in listings depends on the compiler: Chinese comments work fine under XeLaTeX; older engines (latex/pdfLaTeX) will produce garbled text. For Chinese documents, always use XeLaTeX for compilation.

Multi-file Projects: \input and \include

Once a document exceeds a few hundred lines, it should be split into files—main.tex serves as the skeleton, and content is divided and conquered.

Example: main.tex Skeleton

\documentclass{ctexart}
\usepackage{amsmath, graphicx, booktabs, hyperref}

\begin{document}

\input{chapters/intro}     % Introduction (filename without .tex)
\input{chapters/method}    % Method
\input{chapters/result}    % Experiments
\input{chapters/conclusion}% Conclusion

\bibliographystyle{plain}
\bibliography{refs}

\end{document}

The two commands look similar but have clear behavioral differences:

Comparison	\input{file}	\include{file}
Can be nested	Yes (sub-files can further use input)	No
Forces page break	No	Each file starts with a forced \clearpage
Works with \includeonly	No	Yes; compiles only specified chapters (great for speed)
Suitable granularity	Arbitrary snippets (macros, figures, covers)	Chapter-level large blocks

Common pitfall: \include forces a page break. Using it to stitch "several subsections on the same page" will cause mysterious page breaks—always use \input for small snippets.

latexmk: One-click Compilation

The four-step compilation pipeline from Chapter 9 is painful to type manually; latexmk automates it.

$ latexmk -xelatex main.tex    # XeLaTeX engine, automatically runs all passes
$ latexmk -xelatex -C main.tex # Clean intermediate files together
$ latexmk -xelatex -c main.tex # Keep PDF, clean auxiliary files

latexmk automatically decides: if there is bibtex or changes in table-of-contents references, it compiles more times until all numbers stabilize. In the editor, configure the "build command" as latexmk -xelatex main.tex.

Troubleshooting Mindset

LaTeX error messages start with an exclamation mark and include a line number. The format is fixed; reading the first few lines is enough.

! Undefined control sequence.

l.42 \section{Method}

l.42 points to the offending line—in this example, line 42 misspelled \section as \secton. Fix this one place, and a chain of follow-up errors often disappears together.

Error Message	Meaning	Handling
Undefined control sequence	Command does not exist: spelling error or missing package	Check spelling against the line number; confirm package is loaded
Missing $ inserted	Math command appears in text mode	Put \alpha etc. inside $ $
File xxx not found	File or package not found	Check path; tlmgr install xxx
Runaway argument	Environment not closed (missing \end)	Add \end{...} at the indicated line
LaTeX Error: Environment xxx undefined	Used an undefined environment	Check environment spelling and package
! Emergency stop	Compilation completely stopped	Scroll up in the log to find the first error
Reference undefined (warning)	Reference is ??	Compile again

Always fix only the first error in the log—the later errors are mostly chain reactions of the first. Recompile after fixing, which is much more reliable than changing ten places at once.

Summary

Need	Solution
Reduce repeated input	Define commands and environments with \newcommand
Post code	listings + \lstset global styles
Split large documents	\input (snippets) / \include (chapters)
One-click compilation	latexmk -xelatex
Troubleshooting	Read the line number of the first ! error