Floats & Protection

The subjects from the title are completely unrelated. But they were too short to receive their own chapter, which is why I’ll discuss both at once.

With the table environment from last chapter, we’ve already seen a floating body. Any type of complex figure, like tables or pictures, is a floating body.

This means that LaTeX is able to float this environment around the document until it finds a position where it fits. It’s called floating, and not repositioning, because it’s a fluid operation. All other text and environments try to nicely float around it.

For example, say you declare a table to be here (with the h position specifier). But the table is too large to fit on this page. Then LaTeX tries pushing it to the next page.

However, instead of pushing the whole document underneath it down as well, it simply lets other text take its position. Other smaller elements fill the leftover space, so it doesn’t leave a big white gap.

If LaTeX can’t immediately place a figure, it places it into a queue. Then, the next time it finds space to place something, it drops the first item from the queue there. This means that floating bodies influence each other—if one of them is pushed downwards, all of them need to wait a little longer. This is usually not what you want, and if your document looks jammed up, you should check if there’s a floating body that is pushing everything away.

Because LaTeX keeps track of all tables and figures, you can use a single command to display a list of all of them. The command is \listoftables for tables, and \listoffigures for figures.

 1% This repeated 3 times, with different captions
 2\begin{table}[h]
 3    \centering
 4    \begin{tabular}{l | l | l}
 5        Cell 1 & Cell 2 & Cell 3 \
 6        Cell 1 & Cell 2 & Cell 3
 7    \end{tabular}
 8    \caption{What a nice table this is.}
 9\end{table}
10
11% What this code example is all about:
12\listoftables

If you want LaTeX to just immediately dump everything in its queue, use \clearpage. Use \cleardoublepage if you want it to start from a right-hand page.

The float Package

We’ve already seen several environments using the same list of specifiers that show a preference for a certain position. (Such as: top or bottom of the page?)

But, because LaTeX is just trying its best without certainty, floating bodies might not end up where you want them to be. If you want to force them at an exact position, you need two things:

• Include the float package
• Use the H position specifier. Yes, capital letter.

 1\usepackage{float}
 2
 3\begin{document} A first paragraph.
 4    \begin{table}[H]
 5        \centering
 6        \begin{tabular}{l | l | l}
 7            Cell 1 & Cell 2 & Cell 3 \
 8            Cell 1 & Cell 2 & Cell 3
 9        \end{tabular}
10        \caption{What a nice table this is.}
11    \end{table} A second paragraph.
12\end{document}

Protection

There are commands which we call fragile.

They can be carried over or copied. This means other processes rely on them existing or being correct. If not, compilation crashes and burns—which is why we call them fragile.

For example, if you create a table of contents, all text within \section and \subsection commands is automatically copied over.

If you use a special command within that text, it’s possible that this process fails. LaTeX doesn’t know what to do. Compilation fails, probably with mysterious errors.

To protect fragile commands in these cases, use \protect in front of them. This only affects the command right after it—not even its arguments.

1\section{I am considerate \protect\footnote{and protect my footnotes}} 
2Lorem Ipsum...