Let’s Learn LaTex: Part 3

Welcome back to my Let’s Lern LaTex series. I haven’t done any of these posts in a while, but that doesn’t mean i gave up on the idea. Today I want to show you lists which interestingly enough work very much like their corresponding structures in HTML.

For example, LaTex has 3 basic list environments: enumerated list, itemized list and description list. Sounds familiar? It should because these correspond to the ordered list (<ol>), unordered list (<ul>) and definition list (<dl>) in HTML. Let me show you some quick examples – these should be self explanatory.

First let’s do the enumerated list:

\begin{enumerate}
	\item First item
	\item Second item
	\item Third item
\end{enumerate}

As you can see it is a standard environment just like the ones I have shown you before. The only difference is that you preface each item on the list with an \item command. Here is a sample output:

Enumerated list

Itemized list is identical in syntax:

\begin{itemize}
	\item First item
	\item Second item
	\item Third item
\end{itemize}

Here is the output:

Itemized list

Description list is actually even easier to make than in HTML because you don’t need two sets of tags. In the description environment the item command takes an argument which is the word/phrase that is to be used as the word to be defined/described:

\begin{description}
	\item[Foo] Some long description that will probably wrap to the next line, because that's what we want to show. Note how the wrap around works in this case, indenting the second line 
	\item[Bar] And even longer description that will probably wrap to the next line, because that's what we want to show. Actually, this one may not be as long. Whatever.
\end{description}

Note that Foo an Bar are user defined values – you can put whatever you want in there. Here is how it looks once compiled:

Description List

If you want to make lists with multiple indentation levels, you do the same exact thing you would do in HTML: you nest two or three lists like this:

\begin{enumerate}
	\item First item
	\item Second item	
		\begin{enumerate}
			\item First Sub item
				\begin{enumerate}
				    \item First sub sub item
				    \item Second sub sub item
				\end{enumerate}				
			\item Second Sub item
			\item Third Sub item
		\end{enumerate}
	\item Third item
\end{enumerate}

Here is how it would look – note that the counter type changes automatically so that the first level is numbers, second level is characters, third level is roman numerals and etc:

Nested list

First thing people ask after they learn how to use lists is how to change their appearance. For example, how to make enumerated list start with upper case roman numerals instead of numbers. Well, it is not the most straightforward thing to do conceptually. I mean, it can be accomplished in one line, but understanding what is a whole other thing.

You see, in LaTex you can redefine every single command and change what it does. Yep, it is one of those languages where almost nothing is holly and even the most basic operators can be tampered with. This is one of the features that makes LaTex so flexible. To change the way lists work, you basically go in, and you alter the command that LaTex uses internally to display list labels and counters.

By default LaTex recognizes following counter styles:

\arabic	% 1, 2, 3 ...
\alph 	% a, b, c ...
\Alph 	% A, B, C ...
\roman	% i, ii, iii ...
\Roman	% I, II, III ...

You use them like this:

\renewcommand{\labelenumi}{\Roman{enumi}.}

This may seem a bit difficult to grasp but basically in plain english we would say that \renewcommand command redefines the \labelenumi command (which prints out the first level list label) by applying the \Roman style to the first level counter. Does that make sense? If you want to change second and third level, you follow the same pattern:

\renewcommand{\labelenumii}{\roman{enumii}--}
\renewcommand{\labelenumiii}{\{\alph{enumiii}\}}

As you can see, the last argument can be formatted any way you like. You can add dots, parentheses, dashes and etc.. These settings will affect the rest of the document from the point where you first specify them, so if you want to mix and match styles you will need to do this several times in your document. Here is a sample output:

Modified list

Itemized lists can be modified as well using the following command:

\renewcommand{\labelitemi}{\textgreater}

This will change the default bullet to \textgreater which prints out the greater-than symbol like this:

Modified itemized list

There are many symbols you can use as bullets. There is a wide range of them you can find here for example. In general, just google “LaTex Symbols” and you should be all set. If you use a symbol command and you get compilation errors just surround it in $ marks like this:

\renewcommand{\labelitemi}{$\clubsuit$}

This will give you nice club symbols for bullets:

Modified itemized list with math mode

The dollar sign symbols enter LaTex math mode – but you don’t have to worry about that yet. I will talk about it at length in one of the next posts. For now just keep in mind that some symbols are only accessible after you surround them with dollar signs.

I wanted to talk about tables in the same post, but I realized that this post is already getting long so I will stop here. Next week: tables. And maybe something else if we have space.