2.8.2 Optional Arguments

Some commands may have one or more optional arguments. Unlike mandatory arguments , optional arguments must always be enclosed in square brackets [ ].

Example:

The command \\ ends a line. So the following segment of code:

Line one\\Line two.

will produce the following output:

However the \\ command also has an optional argument that allows you to specify how big the gap between the two lines should be. So the following segment of code:

Line one\\[1cm]Line two.

will produce the following output:

Incidentally, note the difference between the previous example, and the following example:

Line one\\{[1cm]} Line two.

[Start of line goes awry]In this example the [1cm] has been placed inside a group, so it is no longer considered to be an optional argument, and since the command \\ does not take a mandatory argument, the [1cm] is simply interpreted as ordinary text.

Example:

The command \framebox (which will be covered later in §4.7.1. Framed Boxes) takes a mandatory argument and two optional arguments. \framebox puts a frame around the contents of its mandatory argument:

\framebox{Some Text}

The first optional argument can be used to make the box a specified width:

\framebox[4cm]{Some Text}

The second optional argument specifies the justification of the text (left, right or centred) within the box:

\framebox[4cm][r]{Some Text}

In general, if a command has both optional and mandatory arguments, the optional arguments are usually specified first (although there are a few exceptions).

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