\marginpar with options

Question

I was trying to understand what Leslie Lamport said in his book about \marginpar options. He says that

... \marginpar[$\Rightarrow$]{$\Leftarrow$} makes an arrow that points towards the text, whichever margin the note appears in. (Page 59)

I am not sure what he meant by "text". I was hoping that it is the non-marginal text and the arrow would appear in the margin before the margin text. The following is an experiment to test this hypothesis.

\documentclass[11pt]{article}
\usepackage[margin=2in]{geometry}

\begin{document}
This is normal text.%
\marginpar{\em This is a marginal note.}

\vspace{100pt}
This is normal text.%
\marginpar[$\Rightarrow$]{$\Leftarrow$}{\em This is a marginal note.}
\end{document}  

As you can see the hypothesis is false.

Is it possible to make the arrow followed by the marginal note appear in the margin?

EDIT: Apparently, I did not make myself clear in my first attempt. As you can see in the second example (\marginpar with options) the marginal text (in italic) which is supposed to be in the margin is not in the margin anymore. What I was hoping to see is the following.

If this is not what the options for \Marginpar are there for, then I do not see why I need these options.

Answer 1

lamport didn't say anything about additional text when using the arrows. what he did say is that if you use the option, that's what goes on the odd page instead of what's in the required argument. each argument must be complete with what you want in that margin.

Answer 2

What that meant was that in two-sided layouts, marginal text will change sides depending on whether the page is even or odd – and the optional argument to \marginpar will make it set different text in each case. A more full example would be:

\documentclass{book}

\begin{document}
Odd page\marginpar[$\Rightarrow$]{$\Leftarrow$}
\clearpage
Even page\marginpar[$\Rightarrow$]{$\Leftarrow$}
\end{document}

On an odd page, it sets $\Leftarrow$ in the margin. On an even page, it sets $\Rightarrow$. So the arrow is always pointing toward the body text.

To get an arrow pointing toward the margin note, just say:

\marginpar{$\Rightarrow$ Some text}

Or for an arrow that always points from the body to the margin:

\marginpar[Some text$\Leftarrow$]{$\Rightarrow$ Some text}