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<body>
<div id="content">
<h1 class="title">My Emacs Notes</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#org6cb6071">Overview</a>
<ul>
<li><a href="#orgd508a24">Introduction</a></li>
<li><a href="#learning">How to learn or lookup features</a></li>
<li><a href="#orgc5e666a">Document Format</a></li>
<li><a href="#org80c44b6">GNU info documentation system</a></li>
</ul>
</li>
<li><a href="#resources">Resources</a>
<ul>
<li><a href="#orge1e3769">General Resources</a></li>
<li><a href="#org1448624">New User Resources</a></li>
<li><a href="#orgc8e3535">Emacs News/RSS/Blog Sites</a></li>
<li><a href="#org338a6d4">Startup Files</a></li>
<li><a href="#org1c02baf">Org Mode</a></li>
</ul>
</li>
<li><a href="#package">Package</a>
<ul>
<li><a href="#orge58b3">Package Overview</a></li>
</ul>
</li>
<li><a href="#orgd103a2a">Emacs-Lisp</a>
<ul>
<li><a href="#elisp_basics">Elisp Basics</a></li>
<li><a href="#expressions">Elisp Expressions</a></li>
<li><a href="#symbols">Symbols</a></li>
<li><a href="#advising">Advising</a></li>
</ul>
</li>
</ul>
</div>
</div>

<div id="outline-container-org6cb6071" class="outline-2">
<h2 id="org6cb6071">Overview</h2>
<div class="outline-text-2" id="text-org6cb6071">
</div><div id="outline-container-orgd508a24" class="outline-3">
<h3 id="orgd508a24">Introduction</h3>
<div class="outline-text-3" id="text-orgd508a24">
<p>
This is my collection of GNU/Emacs related notes which I wrote for my
own use as well as to share with my friends and colleagues.
This may be a bit chaotic, because much of it was lifted from a much larger
document which I have been carrying around for many years.
</p>

<p>
<b>Warning</b>: many links are not properly rendered by github.
Please see <a href="README.html">README.org</a> on how best to read this document.
</p>

<p>
This document is written in <a href="http://www.gnu.org/software/emacs/manual/html_mono/org.html#Top">org-mode</a>. It is best viewed using emacs in org
format, but you can also view the HTML version via a web browser.
</p>

<p>
Why another document on emacs when there are so many online resources already?
Although there are many online resources, almost none of them cross link to the
official manuals which I think is quite unfortunate, because in my opinion one
of the best things about emacs is its excellent documentation which can be
accessed from within emacs in many ways.
</p>

<p>
The <a href="http://www.gnu.org/software/emacs/tour/">Official Guided Tour</a> is just about the only online resource that I could
find that has more than a few links to the official manuals. Unfortunately this
document does not seem to refer to any unofficial resources outside of <a href="http://gnu.org">gnu.org</a>,
e.g., there is no mention of packages such as <a href="https://github.com/magit/magit">magit</a>, <a href="https://gitorious.org/evil/evil.git">evil</a>, and many many other
excellent packages some of which are mentioned in this document. My goals with
this document is to help my friends and colleagues not only learn many
features of emacs, but also to get them well versed in emacs documentation
system so that they can learn all that emacs has to offer on their own.
</p>

<p>
This document cross links heavily with the official manuals
such as the <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Top">Emacs Manual</a> and the <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Top">Emacs-Lisp Manual</a>.
If you are reading this document within emacs as org files, then clicking on
these links bring up GNU <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Top">info</a> browser.  If you are reading the html version
(e.g., <a href="https://github.com/emacs18/notes">https://github.com/emacs18/notes</a>), then most emacs related links
will take you to documents located under
<a href="http://www.gnu.org/software/emacs/manual/html_mono">http://www.gnu.org/software/emacs/manual/html_mono</a>.
</p>
</div>
</div>

<div id="outline-container-org308d8f1" class="outline-3">
<h3 id="learning"><a id="org308d8f1"></a>How to learn or lookup features</h3>
<div class="outline-text-3" id="text-learning">
<p>
The chapter of emacs manual details many ways to get help.
Also <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Top">info manual</a> is a good way to learn the GNU info browser.
A few of the topics discussed in these manuals are listed below.
</p>

<ul class="org-ul">
<li>Hitting <code>C-h</code> or <code>?</code> following any incomplete key sequence will list all
possible key bindings, e.g., try typing <code>C-x 4 C-h</code>.
Also <a href="https://github.com/justbur/emacs-which-key">which-key</a> add-on package shows all possible key bindings as you type.</li>
<li>Type <code>C-h C-h</code> to see what commands follow <code>C-h</code> and learn as many of these
as possible.</li>
<li>helm is another great way.  Just type <code>M-x</code> and start typing space separate
regexp of the command that you want to locate, e.g., typing "back color"
shows that <code>set-background-color</code> is the only match.</li>
</ul>

<p>
Some of the commands that start with <code>C-h</code> are:
</p>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">


<colgroup>
<col  class="org-left" />

<col  class="org-left" />

<col  class="org-left" />
</colgroup>
<thead>
<tr>
<th scope="col" class="org-left">Key</th>
<th scope="col" class="org-left">Function</th>
<th scope="col" class="org-left">Comment</th>
</tr>
</thead>
<tbody>
<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Top">C-h i</a></td>
<td class="org-left">info</td>
<td class="org-left">launch GNU/info browser</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Key-Help">C-h k</a></td>
<td class="org-left">describe-key</td>
<td class="org-left">describe specified key sequence</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Name-Help">C-h f</a></td>
<td class="org-left">describe-function</td>
<td class="org-left">describe specified function</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Name-Help">C-h v</a></td>
<td class="org-left">describe-variable</td>
<td class="org-left">describe specified variable</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Misc-Help">C-h S</a></td>
<td class="org-left">info-lookup-symbol</td>
<td class="org-left">locate manual section on specified symbol</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Major-Modes">C-h m</a></td>
<td class="org-left">describe-mode</td>
<td class="org-left">summary of current major mode</td>
</tr>

<tr>
<td class="org-left"><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Apropos">C-h a</a></td>
<td class="org-left">apropos-command</td>
<td class="org-left">find symbols by name</td>
</tr>
</tbody>
</table>
</div>
</div>

<div id="outline-container-orgc5e666a" class="outline-3">
<h3 id="orgc5e666a">Document Format</h3>
<div class="outline-text-3" id="text-orgc5e666a">
<p>
This document is authored in <a href="http://orgmode.org">org-mode</a> format within GNU/Emacs, then converted to
HTML via emacs. I prefer to use the <i>bigblow</i> HTML theme provided by
<a href="https://github.com/fniessen/org-html-themes">org-html-themes</a> add-on package.
</p>

<p>
I started writing this document in <a href="http://www.gnu.org/software/texinfo/">texinfo</a> format, but then switched over to
using <a href="http://www.gnu.org/software/emacs/manual/html_mono/org.html#Top">org-mode</a>.
</p>

<p>
Although most folks probably read HTML version of this document, I read and
edit this document in org format.  One key advantage of org mode is that
links to Emacs and Elisp manuals pop up instantaneously without any delay.
</p>

<p>
Most links to the <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Top">info</a> documents are presented using info node name notation,
e.g., <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Help">(emacs)Help</a>.   See <a href="#org80c44b6">GNU info documentation system</a> below for more info.
</p>
</div>
</div>

<div id="outline-container-org80c44b6" class="outline-3">
<h3 id="org80c44b6">GNU info documentation system</h3>
<div class="outline-text-3" id="text-org80c44b6">
<p>
If you hit <code>C-h i</code> or <code>M-x info</code> within emacs, it brings up the <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Top">info</a> document
browser which allows you to browse many info documents. Hitting <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Help-Int">d</a> within the
info browser displays all the info files that are currently known to emacs.
From there you can browse <i>emacs</i>, <i>elisp</i>, or any other document currently
available.
</p>
</div>
</div>
</div>

<div id="outline-container-org9f790eb" class="outline-2">
<h2 id="resources"><a id="org9f790eb"></a>Resources</h2>
<div class="outline-text-2" id="text-resources">
<p>
This chapter lists some of the online emacs resources available that I
came across over the years.
</p>
</div>

<div id="outline-container-orge1e3769" class="outline-3">
<h3 id="orge1e3769">General Resources</h3>
<div class="outline-text-3" id="text-orge1e3769">
<p>
There are just too many resources, but here is my collection of few links.
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/">Emacs Official Home Page</a> has more modern look and feel as of early 2016.</li>
<li><a href="http://emacswiki.org">Emacs Wiki</a> is not "official", but it is
perhaps the best resource in terms of variety of topics covered.</li>
<li><a href="http://en.wikipedia.org/wiki/Emacs">wikipedia article</a> provides good history of emacs.</li>
<li><a href="http://www.masteringemacs.org">masteringemacs</a> covers a book with the same name, but it also has
links to some useful articles as well.
<a href="http://www.masteringemacs.org/reading-guide">Reading Guide</a> link at the top seems
especially useful.</li>
<li><a href="http://directory.fsf.org/wiki/Emacs">Official Wiki</a> does not seem to be that useful.</li>
<li><a href="https://plus.google.com/communities/114815898697665598016">Google+ community</a> with over 9000 members as of May 2015.</li>
<li><a href="http://emacs.stackexchange.com/">Emacs at stackexchange</a></li>
<li><a href="http://tuhdo.github.io/">Tu Do's excellent documents</a> have lots of GIF animations.</li>
<li><a href="http://www.finseth.com/emacs.html">Emacs Implementations and Literature</a> has encyclopedic collection of different
implementations of emacs or emacs-like programs, emacs related books, and
other online resources.</li>
<li><a href="http://declank.com/building-and-debugging-gnu-emacs-part-1/">Building and Debugging GNU Emacs: Part 1</a> by Declan Kelly seems to have good
info on how to build emacs on linux as well as debug.</li>
<li><a href="http://www.reddit.com/r/emacs/comments/3ge5ad/scifi_author_tony_ballantyne_on_emacs/">SciFi author Tony Ballantyne on emacs</a>
covers how a writer uses emacs to write articles and books</li>
</ul>
</div>
</div>

<div id="outline-container-org1448624" class="outline-3">
<h3 id="org1448624">New User Resources</h3>
<div class="outline-text-3" id="text-org1448624">
<ul class="org-ul">
<li><a href="emacs-lisp-intro.html#Top">An Introduction to Programming in Emacs Lisp</a></li>
<li><a href="http://www.gnu.org/software/emacs/tour/">Official Guided Tour</a>
gives good overview of emacs features with links to emacs manuals.
One drawback is that this does not refer to resources that are not
"official", e.g., it mentions viper, but not <a href="https://gitorious.org/evil/evil.git">evil</a>.</li>
<li><a href="http://www.emacswiki.org/emacs/EmacsNewbie">EmacsNewbie at emacswiki</a> lists other resources for new users.</li>
<li><a href="http://www.star.bris.ac.uk/bjm/emacs-tips.html">Emacs Tips</a> is someone's attempt at providing emacs tips to colleagues.
It would be nice if I could join forces with folks like this so that we can
create an org document with cross links to the manuals.</li>
<li><a href="http://emacslife.com/how-to-read-emacs-lisp.html">Read Lisp, Tweak Emacs: How to read Emacs Lisp so that you can customize Emacs</a></li>
</ul>
</div>
</div>

<div id="outline-container-orgc8e3535" class="outline-3">
<h3 id="orgc8e3535">Emacs News/RSS/Blog Sites</h3>
<div class="outline-text-3" id="text-orgc8e3535">
<p>
There are many blog and other site.
These are just a few that I came across.
</p>

<ul class="org-ul">
<li><a href="http://endlessparentheses.com/">Endless Parentheses</a> is a blog which often has good articles</li>
<li><a href="http://www.lunaryorn.com/">lunarsite</a> is another blog site</li>
<li><a href="https://emacs.zeef.com/ehartc">Ernst de Hart</a> - collection of packages categorized by topic</li>
<li><a href="http://planet.emacsen.org/">Planet Emacsen</a> - RSS Feed</li>
<li><a href="http://emacsredux.com/">Emacs Redux</a> (last updated on <span class="timestamp-wrapper"><span class="timestamp">[2015-01-15 Thu]</span></span>)</li>
<li><a href="http://emacs-fu.blogspot.com/">emacs-fu</a> (last updated on <span class="timestamp-wrapper"><span class="timestamp">[2013-03-17 Sun]</span></span>)</li>
<li><a href="http://batsov.com/articles/2011/11/30/the-ultimate-collection-of-emacs-resources/">Batsov's Collection of Resources</a> (last updated on <span class="timestamp-wrapper"><span class="timestamp">[2011-11-30 Wed]</span></span>)</li>
</ul>
</div>
</div>

<div id="outline-container-org338a6d4" class="outline-3">
<h3 id="org338a6d4">Startup Files</h3>
<div class="outline-text-3" id="text-org338a6d4">
<p>
These links discuss emacs startup files.
There are many others I'm sure.
</p>

<ul class="org-ul">
<li><a href="http://doc.norang.ca/org-mode.html">Bernt Hansen</a> - "Org Mode - Organize Your Life In Plain Text!" is an excellent
resource on org-mode as well as many things emacs related.</li>
<li><a href="http://oremacs.com/2015/04/24/oremacs-config/">Oleh Krehel</a></li>
<li><a href="http://pages.sachachua.com/.emacs.d/Sacha.html">Sacha Chua</a></li>
<li><a href="https://github.com/grettke/home">grettke</a> (see ALEC.org)</li>
<li><a href="https://github.com/larstvei/dot-emacs">Lars Tveito</a></li>
<li>Ryan Rix: <a href="http://fort.kickass.systems:10082/cgit/fsem.git/tree/">org source</a>, <a href="http://doc.rix.si/org/fsem.html">html version</a>, <a href="http://rix.si/blog/2015/01/05/fsem-001/">2015/01/05 blog</a></li>
</ul>
</div>
</div>

<div id="outline-container-org1c02baf" class="outline-3">
<h3 id="org1c02baf">Org Mode</h3>
<div class="outline-text-3" id="text-org1c02baf">
<p>
Some links on org mode:
</p>

<ul class="org-ul">
<li><a href="http://orgmode.org">org-mode home page</a></li>
<li><a href="http://orgmode.org/worg">worg</a></li>
<li><a href="http://www.emacswiki.org/emacs/OrgMode">OrgMode at emacswiki</a></li>
<li><a href="http://orgmode.org/worg/dev/">worg dev</a></li>
<li><a href="http://doc.norang.ca/org-mode.html">Bernt Hansen</a> - "Org Mode - Organize Your Life In Plain Text!"</li>
<li><a href="http://orgmode.org/worg/org-tutorials/">Tutorials at worg</a></li>
<li><a href="https://www.youtube.com/watch?v=1-dUkyn_fZA&amp;feature=youtube_gdata_player">Emacs + org-mode + python in reproducible research; SciPy 2013 Presentation</a></li>
<li><a href="http://home.fnal.gov/~neilsen/notebook/orgExamples/org-examples.html">Emacs org-mode examples and cookbook</a> - lots of neat ways to use org</li>
</ul>
</div>
</div>
</div>

<div id="outline-container-orgcfc1ad8" class="outline-2">
<h2 id="package"><a id="orgcfc1ad8"></a>Package</h2>
<div class="outline-text-2" id="text-package">
</div>

<div id="outline-container-orge58b3" class="outline-3">
<h3 id="orge58b3">Package Overview</h3>
<div class="outline-text-3" id="text-orge58b3">
<p>
For an overview see <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Packages">Packages</a> section of Emacs manual, and <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging">Packaging</a> section of
Emacs-Lisp manual. Also you should be familiar with the following concepts
explained in <a href="#elisp_basics">Elisp Basics</a> section to understand this section:
<i>loading</i>, <i>autoload</i>, <code>load-path</code>, <i>byte-compiling</i>, etc.
</p>

<p>
A package is a collection of files.  Most often the files are elisp files, but
it could also include info manuals and other files.  Installing a package
usually means
</p>

<ul class="org-ul">
<li>Creating a new sub-directory under the directory specifiied by
<a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging-Basics">package-user-dir</a> variable</li>
<li>Unpacking files (usually from a tarball) to the new directory</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Byte-Compilation">Byte-compiling</a> all elisp files.</li>
<li>Generating the <i>autoload file</i>, i.e., a file that contains <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Lisp-Libraries">autoload</a> forms.</li>
<li>Generating info manuals from texinfo source files if any</li>
</ul>

<p>
Once installed, a package needs to be <b>activated</b> to make it available for use.
This includes three things
</p>
<ul class="org-ul">
<li>add installed package directory to <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Library-Search">load-path</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Loading">Load</a> the autoload file, i.e., <code>&lt;package&gt;-autoloads.el</code> file found in the
package install directory if any</li>
<li>add package directory to <a href="http://www.gnu.org/software/emacs/manual/html_mono/info.html#Emacs-Info-Variables">info-directory-list</a> if the package comes with GNU
info manual</li>
</ul>

<p>
All installed packages are <b>activated</b> on emacs startup, i.e., emacs searches
all sub-directories of <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging-Basics">package-user-dir</a> and activates them.
</p>

<p>
Following are few variables which control package installation as well activation:
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Package-Archives">package-archives</a> determines package sources, i.e., location from which to
find packages</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging-Basics">package-user-dir</a> determines where packages get installed</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging-Basics">package-load-list</a> determines which
packages are initialized on startup among all the installed
package.  Default is to initialize all.</li>
</ul>

<p>
Following are some of the functions related with packaging:
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Package-Menu">list-packages</a> pops up "GUI" buffer so
that you can browes, install, and delete packages interactively.</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Packaging-Basics">package-initialize</a> is implicitly called by default <b>after</b>
evaluating <code>~/.emacs</code>.  However you can also call this explicitly
in your <code>~/.emacs</code> early on to <b>activate</b> installed packages.</li>
</ul>
</div>
</div>
</div>

<div id="outline-container-orgd103a2a" class="outline-2">
<h2 id="orgd103a2a">Emacs-Lisp</h2>
<div class="outline-text-2" id="text-orgd103a2a">
</div><div id="outline-container-org33e5eb9" class="outline-3">
<h3 id="elisp_basics"><a id="org33e5eb9"></a>Elisp Basics</h3>
<div class="outline-text-3" id="text-elisp_basics">
<p>
This chapter points out a few basic emacs-lisp concepts to help
you understand how to install and use add-on packages.
More comprehensive resources on learning elisp are listed at
<a href="#org1448624">New User Resources</a>
</p>

<p>
Topics covered include
</p>
<ul class="org-ul">
<li>elisp files define functions, variables, and other objects</li>
<li>emacs loads (i.e., evaluates) files to pick up new functions, and also
possibly modify built-in features</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Library-Search">load-path</a> tells emacs where to find elisp files</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Lisp-Libraries">autoload</a> allows easy access to functions without using too much memory</li>
<li>elisp files are byte-compiled mainly for faster execution</li>
</ul>

<p>
The core emacs code is written in C.  However much of built-in features of emacs
is written in emacs-lisp which is a lisp dialect customized for use within
emacs.  The core of emacs is the elisp <b>interpreter</b> (or a <b>virtual machine</b>).
When you use emacs you are interacting with the interpreter which is in
infinite <b>REPL</b>, i.e., <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Command-Loop">Read-Eval-Print-Loop</a>.  It just sits there and waits for
you to use input devices such as keyboards and mice to request actions.
</p>

<p>
When you type anything on the keyboard or use mouse, you are executing elisp
function bound to the key or mouse event that you just invoked.  For example if
you type <code>m</code>, then you are asking the interpreter to call <code>self-insert-command</code>
elisp function which just inserts the letter just typed into the current buffer.
However <code>m</code> is bound to <code>dired-mark</code> elisp function instead of
<code>self-insert-command</code> within buffers in <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Dired">dired-mode</a> so that typing <code>m</code> results
not in inserting letter <code>m</code>, but marking the current item in dired buffer.
See <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Keys">Keys</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Keys">Commands</a>.
</p>

<p>
You can use <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Key-Help">C-h k</a> to ask emacs to describe what any given key sequence would
do rather than calling the function bound to that key sequence.  For example
typing <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Key-Help">C-h k</a> followed by <code>m</code> in most buffers would say that the <code>m</code> key
sequence is bound to <code>self-insert-command</code>.  Similarly typing <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Key-Help">C-h k</a> followed
by <code>C-x C-f</code> brings up <code>*Help*</code> buffer describing <a href="http://www.gnu.org/software/emacs/manual/html_mono/emacs.html#Basic-Files">find-file</a> function.
<code>*Help*</code> buffer should show <b>files.el</b> link at the top.<sup><a id="fnr.1" class="footref" href="#fn.1">1</a></sup>
Clicking your mouse button on this <b>files.el</b> link
should bring up <code>files.el</code> file showing emacs-lisp code that
implements <code>find-file</code> function, i.e., you can browse the source code that make
up emacs.  This is one key reason why I almost always use my own build of emacs
rather than <code>/usr/bin/emacs</code> or other emacs builds provided someone else.
</p>

<p>
Emacs function are written via <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Defining-Functions">defun</a> (among other ways) like this
</p>
<div class="org-src-container">

<pre class="src src-elisp"><span style="color: #3a81c3;">(</span><span style="color: #0000ff; font-weight: bold;">defun</span> <span style="color: #0000ff; font-weight: bold;">f</span> <span style="color: #6c3163;">(</span>arg1 arg2 ...<span style="color: #6c3163;">)</span> ...<span style="color: #3a81c3;">)</span>
</pre>
</div>
<p>
The side effect of evaluation this expression is that the lisp interpreter
has added <code>f</code> function to its internal database of known functions.
Similarly variables are set via <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Global-Variables">setq</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Applying-Customizations">custom-set-variables</a>,
among other ways:
</p>
<div class="org-src-container">

<pre class="src src-elisp"><span style="color: #3a81c3;">(</span><span style="color: #0000ff; font-weight: bold;">setq</span> make-backup-files nil<span style="color: #3a81c3;">)</span>
</pre>
</div>
<p>
Evaluating this make the variable known to emacs.
</p>

<p>
Functions and variables are put in emacs-lisp files such as <code>files.el</code> mentioned
above.  Files are then <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Loading">loaded</a> into emacs, i.e., the content of the file is
<a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Evaluation">evaluated</a> by the elisp interpreter whose side effect is to tuck away the
function and variable definitions so that they can be called or accessed.  In
most cases new emacs-lisp code is made known to the interpreter by loading elisp
files via one of these ways:
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Loading">load-file</a> evaluates the specified file whose side effect is to define
new functions and variables, and also possibly modify existing ones</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Library-Search">load-library</a> first searches the directories listed in <code>load-path</code> (much like
how linux shells search <code>PATH</code>) for the specified file name, then calls
<code>load-file</code> on the located file</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Named-Features">require</a> first search <code>features</code> variable to see if the requested module
is already loaded or not.  If is is already loaded, then nothing is done.
If it is not, then <code>load-library</code> is called.</li>
</ul>

<p>
However you can also <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Evaluation">evaluate</a> specific elisp expressions within
buffers interactively via
<code>eval-last-sexp</code> (bound to <code>C-x C-e</code>),
<code>eval-print-last-sexp</code>,
<code>eval-region</code>,
<code>eval-current-buffer</code>,
<code>eval-expression</code>,
etc.
</p>
</div>
</div>

<div id="outline-container-orgb04c20d" class="outline-3">
<h3 id="expressions"><a id="orgb04c20d"></a>Elisp Expressions</h3>
<div class="outline-text-3" id="text-expressions">
<p>
Resources:
</p>

<ul class="org-ul">
<li>Use the <code>*scratch*</code> buffer to experiment and learn.  Use <code>C-j</code> to
call <code>eval-print-last-sexp</code>.</li>
<li><a href="emacs-lisp-intro.html#Top">emacs-lisp-intro#Top</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Eval">elisp#Eval</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Loading">elisp#Loading</a></li>
</ul>

<p>
Lisp expressions can be evaluated in many ways:
</p>

<ul class="org-ul">
<li><code>C-x C-e</code> bound to <code>eval-last-sexp</code> evaluates one expression at a
time and prints the result in the mini-buffer</li>
<li><code>eval-print-last-sexp</code> evaluates one expression and prints the
result in current buffer.  This is bound to <code>C-j</code> within buffers in
<code>lisp-interaction-mode</code> mode such as <code>*scratch*</code> buffer.</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Eval">eval-region</a> evaluates a region of elisp code</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Eval">eval-buffer</a> evaluates the whole buffer</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#How-Programs-Do-Loading">load</a> evaluates elisp code in a file</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#How-Programs-Do-Loading">load-library</a> evaluates elisp
code in a file but uses LOAD-PATH to locate the requested file</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Named-Features">require</a> looks up
<a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Named-Features">features</a> and if not found, then uses <code>load-libary</code> to
locate and load the file</li>
</ul>
</div>
</div>

<div id="outline-container-org1345b82" class="outline-3">
<h3 id="symbols"><a id="org1345b82"></a>Symbols</h3>
<div class="outline-text-3" id="text-symbols">
<p>
buffer-local dynamic lexical
</p>

<p>
Resources:
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbols">elisp#Symbols</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Variables">elisp#Variables</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Functions">elisp#Functions</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Eval">elisp#Eval</a></li>
</ul>

<p>
Things to note:
</p>

<ul class="org-ul">
<li>a symbol is an object that has for components: name, value,
function and plist</li>
<li>Basic functions are <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbols">symbolp</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Creating-Symbols">symbol-name</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Accessing-Variables">symbol-value</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Creating-Symbols">make-symbol</a>,
<a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Creating-Symbols">intern</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Creating-Symbols">unintern</a>.</li>
<li>Property list functions are:
<a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbol-Plists">get</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbol-Plists">put</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbol-Plists">symbol-plist</a>, <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbol-Plists">set-plist</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Standard-Properties">elisp#Standard Properties</a> lists properties that have
predefined meaning, e.g., <code>disabled</code> and <code>variable-documentation</code>.</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Symbols">obarray</a> is the container with all <a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Creating-Symbols">interned</a> symbols.</li>
<li><code>mapatoms</code> calls a function on all symbols.</li>
</ul>

<p>
Bindings:
</p>
<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Dynamic-Binding">elisp#Dynamic Binding</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Lexical-Binding">elisp#Lexical Binding</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Closures">elisp#Closures</a></li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Using-Lexical-Binding">lexical-binding</a> variable</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Using-Lexical-Binding">special-variable-p</a></li>
</ul>
</div>
</div>

<div id="outline-container-org8f02965" class="outline-3">
<h3 id="advising"><a id="org8f02965"></a>Advising</h3>
<div class="outline-text-3" id="text-advising">
<p>
Official documentation include:
</p>

<ul class="org-ul">
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Advising-Functions">Advising Functions</a> which discuss
the new (as of emacs 24.x) way to advise functions.</li>
<li><a href="http://www.gnu.org/software/emacs/manual/html_mono/elisp.html#Porting-old-advices">Porting old advices</a> shows you
how you can convert old style advices which used <code>defadvice</code> macro.</li>
</ul>

<p>
Advising a functions means modifying the behavior of even built-in emacs
functions to suit your needs.  This is one of the neatest features of
lisp which I haven't yet seen in other languages that I used.  Advising
was first added to emacs in late 1980's or early 1990's in emacs version
</p>
<ol class="org-ol">
<li></li>
</ol>
</div>
</div>
</div>
<div id="footnotes">
<h2 class="footnotes">Footnotes: </h2>
<div id="text-footnotes">

<div class="footdef"><sup><a id="fn.1" class="footnum" href="#fnr.1">1</a></sup> <div class="footpara"><p class="footpara">
If you don't see a link to an elisp file within <code>*Help*</code> buffer, it
probably means that you don't have the elisp source files installed.  On Debian
derived GNU/Linux systems, you can fix this via something like
<code>sudo apt-get install emacs24-el</code>.
</p></div></div>


</div>
</div></div>
<div id="postamble" class="status">
<p class="author">Author: Richard Y. Kim</p>
<p class="date">Created: 2016-04-24 Sun 08:22</p>
<p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
</div>
</body>
</html>