Error With Extract And Hyperref: Classes And Packages Should Only Be Loaded At The Top Level

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Introduction

When working with LaTeX, it's not uncommon to encounter errors related to the loading of classes and packages. In this article, we'll discuss a specific issue that arises when using the extract and hyperref packages in a LaTeX document. We'll provide a minimal working example (MWE) to illustrate the problem and offer solutions to resolve it.

The Minimal Working Example (MWE)

The following LaTeX script is a MWE that reproduces the error:

\documentclass{article}

\usepackage{extract}
\usepackage{hyperref}
\hypersetup{colorlinks=true}


\begin{document}
Test.
\end{document}

This script loads the article class, the extract package, and the hyperref package. The hyperref package is configured to use color links. However, when compiled, this script produces an error.

The Error Message

The error message produced by this script is:

! LaTeX Error: Classes and packages should only be loaded at the top level.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.


l.3 \usepackage{extract}

This error message indicates that the extract package is being loaded at a level other than the top level, which is not allowed.

Understanding the Issue

The issue here is that the hyperref package is being loaded after the extract package. The hyperref package is a complex package that redefines many internal LaTeX commands, including those used by the extract package. When hyperref is loaded after extract, it can cause conflicts and errors.

Solutions

To resolve this issue, we need to load the hyperref package before the extract package. We can do this by rearranging the order of the package loading:

\documentclass{article}

\usepackage{hyperref}
\hypersetup{colorlinks=true}
\usepackage{extract}


\begin{document}
Test.
\end{document}

By loading hyperref before extract, we ensure that the internal LaTeX commands are redefined correctly, and the error is resolved.

Alternative Solution

Another solution is to use the cleveref package, which is designed to work with the hyperref package. We can load cleveref before extract and use its commands to reference equations and sections:

\documentclass{article}

\usepackage{cleveref}
\crefname{equation}{eq.}{eqs.}
\crefname{section}{sec.}{secs.}
\usepackage{hyperref}
\hypersetup{colorlinks=true}
\usepackage{extract}


\begin{document}
Test.
\end{document}

This solution requires more setup, but it provides a more elegant solution to the problem.

Conclusion

In conclusion, the error "Classes and packages should only be loaded at the top level" is caused by loading the hyperref package after the extract package. To resolve this issue, we need to load hyperref before extract. Alternatively, we can use the cleveref package to work around the issue. By understanding the issue and applying the solutions, we can create LaTeX documents that compile correctly and produce the desired output.

Additional Tips

  • Always load packages in the correct order to avoid conflicts and errors.
  • Use the cleveref package to work with the hyperref package and create more elegant references.
  • Experiment with different package loading orders to find the solution that works best for your document.

Related Topics

Introduction

In our previous article, we discussed the error "Classes and packages should only be loaded at the top level" that occurs when using the extract and hyperref packages in a LaTeX document. We provided a minimal working example (MWE) to illustrate the problem and offered solutions to resolve it. In this article, we'll answer some frequently asked questions (FAQs) related to this issue.

Q: What is the correct order of loading packages in LaTeX?

A: The correct order of loading packages in LaTeX is to load them in the order they are required. In general, you should load the article class first, followed by the hyperref package, and then any other packages that require hyperref. For example:

\documentclass{article}

\usepackage{hyperref}
\hypersetup{colorlinks=true}
\usepackage{extract}


\begin{document}
Test.
\end{document}

Q: Why do I need to load hyperref before extract?

A: The hyperref package redefines many internal LaTeX commands, including those used by the extract package. If you load extract before hyperref, it can cause conflicts and errors. By loading hyperref before extract, you ensure that the internal LaTeX commands are redefined correctly.

Q: Can I use cleveref instead of hyperref?

A: Yes, you can use cleveref instead of hyperref. cleveref is designed to work with the hyperref package and provides more elegant references. However, you need to load cleveref before hyperref and configure it correctly.

Q: What are the benefits of using cleveref?

A: The benefits of using cleveref include:

  • More elegant references
  • Automatic numbering of equations and sections
  • Support for multiple reference styles
  • Compatibility with the hyperref package

Q: How do I configure cleveref?

A: To configure cleveref, you need to load it before hyperref and use its commands to reference equations and sections. For example:

\documentclass{article}

\usepackage{cleveref}
\crefname{equation}{eq.}{eqs.}
\crefname{section}{sec.}{secs.}
\usepackage{hyperref}
\hypersetup{colorlinks=true}
\usepackage{extract}


\begin{document}
Test.
\end{document}

Q: What are some common mistakes to avoid when loading packages in LaTeX?

A: Some common mistakes to avoid when loading packages in LaTeX include:

  • Loading packages in the wrong order
  • Loading packages that are not compatible with each other
  • Not loading packages that are required for a specific feature
  • Not configuring packages correctly

Q: How do I troubleshoot package loading errors in LaTeX?

A: To troubleshoot package loading errors in LaTeX, you can:

  • Check the LaTeX manual or online documentation for the package
  • Search online for solutions to similar problems
  • Use the latex command with the -verbose option to get more detailed error messages
  • Use the latex command with the -debug option to get more detailed debugging information

Conclusion

In conclusion, the error "Classes and packages should only be loaded at the top level" is caused by loading the hyperref package after the extract package. To resolve this issue, you need to load hyperref before extract. Alternatively, you can use the cleveref package to work around the issue. By understanding the issue and applying the solutions, you can create LaTeX documents that compile correctly and produce the desired output.

Additional Tips

  • Always load packages in the correct order to avoid conflicts and errors.
  • Use the cleveref package to work with the hyperref package and create more elegant references.
  • Experiment with different package loading orders to find the solution that works best for your document.

Related Topics