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<a name="Using-Octave-Mode"></a>
<div class="header">
<p>
Next: <a href="Running-Octave-from-Within-Emacs.html#Running-Octave-from-Within-Emacs" accesskey="n" rel="next">Running Octave from Within Emacs</a>, Previous: <a href="Installing-EOS.html#Installing-EOS" accesskey="p" rel="prev">Installing EOS</a>, Up: <a href="Emacs-Octave-Support.html#Emacs-Octave-Support" accesskey="u" rel="up">Emacs Octave Support</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Using-Octave-Mode-1"></a>
<h3 class="appendixsec">H.2 Using Octave Mode</h3>

<p>If you are lucky, your sysadmins have already arranged everything so
that Emacs automatically goes into Octave mode whenever you visit an
Octave code file as characterized by its extension <samp>.m</samp>.  If not,
proceed as follows.
</p>
<ol>
<li> To begin using Octave mode for all <samp>.m</samp> files you visit, add the
following lines to a file loaded by Emacs at startup time, typically
your <samp>~/.emacs</samp> file:

<div class="lisp">
<pre class="lisp">(autoload 'octave-mode &quot;octave-mod&quot; nil t)
(setq auto-mode-alist
      (cons '(&quot;\\.m$&quot; . octave-mode) auto-mode-alist))
</pre></div>

</li><li> Finally, to turn on the abbrevs, auto-fill and font-lock features
automatically, also add the following lines to one of the Emacs startup
files:
<div class="lisp">
<pre class="lisp">(add-hook 'octave-mode-hook
          (lambda ()
            (abbrev-mode 1)
            (auto-fill-mode 1)
            (if (eq window-system 'x)
                (font-lock-mode 1))))
</pre></div>
<p>See the Emacs manual for more information about how to customize
Font-lock mode.
</p></li></ol>

<p>In Octave mode, the following special Emacs commands can be used in
addition to the standard Emacs commands.
</p>
<dl compact="compact">
<dt><kbd>C-h m</kbd></dt>
<dd><p>Describe the features of Octave mode.
</p>
</dd>
<dt><kbd>LFD</kbd></dt>
<dd><p>Reindent the current Octave line, insert a newline and indent the new
line (<code>octave-reindent-then-newline-and-indent</code>).  An abbrev before
point is expanded if <code>abbrev-mode</code> is non-<code>nil</code>.
</p>
</dd>
<dt><kbd>TAB</kbd></dt>
<dd><p>Indents current Octave line based on its contents and on previous
lines (<code>indent-according-to-mode</code>). 
</p>
</dd>
<dt><kbd>;</kbd></dt>
<dd><p>Insert an &ldquo;electric&rdquo; semicolon (<code>octave-electric-semi</code>).  If
<code>octave-auto-indent</code> is non-<code>nil</code>, reindent the current line.
If <code>octave-auto-newline</code> is non-<code>nil</code>, automagically insert a
newline and indent the new line.
</p>
</dd>
<dt><kbd>`</kbd></dt>
<dd><p>Start entering an abbreviation (<code>octave-abbrev-start</code>).  If Abbrev
mode is turned on, typing <kbd>`C-h</kbd> or <kbd>`?</kbd> lists all abbrevs.
Any other key combination is executed normally.  Note that all Octave
abbrevs start with a grave accent.
</p>
</dd>
<dt><kbd>M-LFD</kbd></dt>
<dd><p>Break line at point and insert continuation marker and alignment
(<code>octave-split-line</code>).
</p>
</dd>
<dt><kbd>M-TAB</kbd></dt>
<dd><p>Perform completion on Octave symbol preceding point, comparing that
symbol against Octave&rsquo;s reserved words and built-in variables
(<code>octave-complete-symbol</code>). 
</p>
</dd>
<dt><kbd>M-C-a</kbd></dt>
<dd><p>Move backward to the beginning of a function
(<code>octave-beginning-of-defun</code>).
With prefix argument <var>N</var>, do it that many times if <var>N</var> is
positive; otherwise, move forward to the <var>N</var>-th following beginning
of a function.
</p>
</dd>
<dt><kbd>M-C-e</kbd></dt>
<dd><p>Move forward to the end of a function (<code>octave-end-of-defun</code>).
With prefix argument <var>N</var>, do it that many times if <var>N</var> is
positive; otherwise, move back to the <var>N</var>-th preceding end of a
function.
</p>
</dd>
<dt><kbd>M-C-h</kbd></dt>
<dd><p>Puts point at beginning and mark at the end of the current Octave
function, i.e., the one containing point or following point
(<code>octave-mark-defun</code>).
</p>
</dd>
<dt><kbd>M-C-q</kbd></dt>
<dd><p>Properly indents the Octave function which contains point
(<code>octave-indent-defun</code>).
</p>
</dd>
<dt><kbd>M-;</kbd></dt>
<dd><p>If there is no comment already on this line, create a code-level comment
(started by two comment characters) if the line is empty, or an in-line
comment (started by one comment character) otherwise
(<code>octave-indent-for-comment</code>).
Point is left after the start of the comment which is properly aligned.
</p>
</dd>
<dt><kbd>C-c ;</kbd></dt>
<dd><p>Puts the comment character &lsquo;<samp>#</samp>&rsquo; (more precisely, the string value of
<code>octave-comment-start</code>) at the beginning of every line in the
region (<code>octave-comment-region</code>).  With just <kbd>C-u</kbd> prefix
argument, uncomment each line in the region.  A numeric prefix argument
<var>N</var> means use <var>N</var> comment characters.
</p>
</dd>
<dt><kbd>C-c :</kbd></dt>
<dd><p>Uncomments every line in the region (<code>octave-uncomment-region</code>).
</p>
</dd>
<dt><kbd>C-c C-p</kbd></dt>
<dd><p>Move one line of Octave code backward, skipping empty and comment lines
(<code>octave-previous-code-line</code>).  With numeric prefix argument
<var>N</var>, move that many code lines backward (forward if <var>N</var> is
negative).
</p>
</dd>
<dt><kbd>C-c C-n</kbd></dt>
<dd><p>Move one line of Octave code forward, skipping empty and comment lines
(<code>octave-next-code-line</code>).  With numeric prefix argument <var>N</var>,
move that many code lines forward (backward if <var>N</var> is negative).
</p>
</dd>
<dt><kbd>C-c C-a</kbd></dt>
<dd><p>Move to the &lsquo;real&rsquo; beginning of the current line
(<code>octave-beginning-of-line</code>).  If point is in an empty or comment
line, simply go to its beginning; otherwise, move backwards to the
beginning of the first code line which is not inside a continuation
statement, i.e., which does not follow a code line ending in &lsquo;<samp>...</samp>&rsquo;
or &lsquo;<samp>\</samp>&rsquo;, or is inside an open parenthesis list.
</p>
</dd>
<dt><kbd>C-c C-e</kbd></dt>
<dd><p>Move to the &lsquo;real&rsquo; end of the current line (<code>octave-end-of-line</code>).
If point is in a code line, move forward to the end of the first Octave
code line which does not end in &lsquo;<samp>...</samp>&rsquo; or &lsquo;<samp>\</samp>&rsquo; or is inside an
open parenthesis list.  Otherwise, simply go to the end of the current
line.
</p>
</dd>
<dt><kbd>C-c M-C-n</kbd></dt>
<dd><p>Move forward across one balanced begin-end block of Octave code
(<code>octave-forward-block</code>).  With numeric prefix argument <var>N</var>,
move forward across <var>n</var> such blocks (backward if <var>N</var> is
negative).
</p>
</dd>
<dt><kbd>C-c M-C-p</kbd></dt>
<dd><p>Move back across one balanced begin-end block of Octave code
(<code>octave-backward-block</code>).  With numeric prefix argument <var>N</var>,
move backward across <var>N</var> such blocks (forward if <var>N</var> is
negative).
</p>
</dd>
<dt><kbd>C-c M-C-d</kbd></dt>
<dd><p>Move forward down one begin-end block level of Octave code
(<code>octave-down-block</code>).  With numeric prefix argument, do it that
many times; a negative argument means move backward, but still go down
one level.
</p>
</dd>
<dt><kbd>C-c M-C-u</kbd></dt>
<dd><p>Move backward out of one begin-end block level of Octave code
(<code>octave-backward-up-block</code>).  With numeric prefix argument, do it
that many times; a negative argument means move forward, but still to a
less deep spot.
</p>
</dd>
<dt><kbd>C-c M-C-h</kbd></dt>
<dd><p>Put point at the beginning of this block, mark at the end
(<code>octave-mark-block</code>).
The block marked is the one that contains point or follows point.
</p>
</dd>
<dt><kbd>C-c ]</kbd></dt>
<dd><p>Close the current block on a separate line (<code>octave-close-block</code>).
An error is signaled if no block to close is found.
</p>
</dd>
<dt><kbd>C-c f</kbd></dt>
<dd><p>Insert a function skeleton, prompting for the function&rsquo;s name, arguments
and return values which have to be entered without parentheses
(<code>octave-insert-defun</code>).
</p>
</dd>
<dt><kbd>C-c C-h</kbd></dt>
<dd><p>Search the function, operator and variable indices of all info files
with documentation for Octave for entries (<code>octave-help</code>).  If used
interactively, the entry is prompted for with completion.  If multiple
matches are found, one can cycle through them using the standard
&lsquo;<samp>,</samp>&rsquo; (<code>Info-index-next</code>) command of the Info reader.
</p>
<p>The variable <code>octave-help-files</code> is a list of files to search
through and defaults to <code>'(&quot;octave&quot;)</code>.  If there is also an Octave
Local Guide with corresponding info file, say, <samp>octave-LG</samp>, you can
have <code>octave-help</code> search both files by 
</p><div class="lisp">
<pre class="lisp">(setq octave-help-files '(&quot;octave&quot; &quot;octave-LG&quot;))
</pre></div>
<p>in one of your Emacs startup files.
</p>
</dd>
</dl>

<p>A common problem is that the <tt class="key">RET</tt> key does <em>not</em> indent the
line to where the new text should go after inserting the newline.  This
is because the standard Emacs convention is that <tt class="key">RET</tt> (aka
<kbd>C-m</kbd>) just adds a newline, whereas <tt class="key">LFD</tt> (aka <kbd>C-j</kbd>) adds a
newline and indents it.  This is particularly inconvenient for users with
keyboards which do not have a special <tt class="key">LFD</tt> key at all; in such
cases, it is typically more convenient to use <tt class="key">RET</tt> as the <tt class="key">LFD</tt>
key (rather than typing <kbd>C-j</kbd>).  
</p>
<p>You can make <tt class="key">RET</tt> do this by adding
</p><div class="lisp">
<pre class="lisp">(define-key octave-mode-map &quot;\C-m&quot;
  'octave-reindent-then-newline-and-indent)
</pre></div>
<p>to one of your Emacs startup files.  Another, more generally applicable
solution is
</p><div class="lisp">
<pre class="lisp">(defun RET-behaves-as-LFD ()
  (let ((x (key-binding &quot;\C-j&quot;)))
    (local-set-key &quot;\C-m&quot; x)))
(add-hook 'octave-mode-hook 'RET-behaves-as-LFD)
</pre></div>
<p>(this works for all modes by adding to the startup hooks, without having
to know the particular binding of <tt class="key">RET</tt> in that mode!).  Similar
considerations apply for using <tt class="key">M-RET</tt> as <tt class="key">M-LFD</tt>.  As Barry
A. Warsaw <a href="mailto:bwarsaw@cnri.reston.va.us">bwarsaw@cnri.reston.va.us</a> says in the documentation for his
<code>cc-mode</code>, &ldquo;This is a very common question.  <code>:-)</code> If you want
this to be the default behavior, don&rsquo;t lobby me, lobby RMS!&rdquo;
</p>
<p>The following variables can be used to customize Octave mode.
</p>
<dl compact="compact">
<dt><code>octave-auto-indent</code></dt>
<dd><p>Non-<code>nil</code> means auto-indent the current line after a semicolon or
space.  Default is <code>nil</code>.
</p>
</dd>
<dt><code>octave-auto-newline</code></dt>
<dd><p>Non-<code>nil</code> means auto-insert a newline and indent after semicolons
are typed.  The default value is <code>nil</code>.
</p>
</dd>
<dt><code>octave-blink-matching-block</code></dt>
<dd><p>Non-<code>nil</code> means show matching begin of block when inserting a space,
newline or &lsquo;<samp>;</samp>&rsquo; after an else or end keyword.  Default is <code>t</code>.
This is an extremely useful feature for automatically verifying that the
keywords match&mdash;if they don&rsquo;t, an error message is displayed.
</p>
</dd>
<dt><code>octave-block-offset</code></dt>
<dd><p>Extra indentation applied to statements in block structures.
Default is 2.
</p>
</dd>
<dt><code>octave-continuation-offset</code></dt>
<dd><p>Extra indentation applied to Octave continuation lines.
Default is 4. 
</p>
</dd>
<dt><code>octave-continuation-string</code></dt>
<dd><p>String used for Octave continuation lines.
Normally &lsquo;<samp>\</samp>&rsquo;.
</p>
</dd>
<dt><code>octave-mode-startup-message</code></dt>
<dd><p>If <code>t</code> (default), a startup message is displayed when Octave mode
is called.
</p>
</dd>
</dl>

<p>If Font Lock mode is enabled, Octave mode will display
</p>
<ul>
<li> strings in <code>font-lock-string-face</code>

</li><li> comments in <code>font-lock-comment-face</code>

</li><li> the Octave reserved words (such as all block keywords) and the text
functions (such as &lsquo;<samp>cd</samp>&rsquo; or &lsquo;<samp>who</samp>&rsquo;) which are also reserved
using <code>font-lock-keyword-face</code>

</li><li> the built-in operators (&lsquo;<samp>&amp;&amp;</samp>&rsquo;, &lsquo;<samp>==</samp>&rsquo;, &hellip;) using
<code>font-lock-reference-face</code>

</li><li> and the function names in function declarations in
<code>font-lock-function-name-face</code>.
</li></ul>

<p>There is also rudimentary support for Imenu (currently, function names
can be indexed).
</p>
<a name="index-TAGS"></a>
<a name="index-Emacs-TAGS-files"></a>
<a name="index-octave_002dtags"></a>
<p>You can generate TAGS files for Emacs from Octave <samp>.m</samp> files using
the shell script <code>octave-tags</code> that is installed alongside your copy of
Octave.
</p>
<p>Customization of Octave mode can be performed by modification of the
variable <code>octave-mode-hook</code>.  If the value of this variable is
non-<code>nil</code>, turning on Octave mode calls its value.
</p>
<p>If you discover a problem with Octave mode, you can conveniently send a
bug report using <kbd>C-c C-b</kbd> (<code>octave-submit-bug-report</code>).  This
automatically sets up a mail buffer with version information already
added.  You just need to add a description of the problem, including a
reproducible test case and send the message.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Running-Octave-from-Within-Emacs.html#Running-Octave-from-Within-Emacs" accesskey="n" rel="next">Running Octave from Within Emacs</a>, Previous: <a href="Installing-EOS.html#Installing-EOS" accesskey="p" rel="prev">Installing EOS</a>, Up: <a href="Emacs-Octave-Support.html#Emacs-Octave-Support" accesskey="u" rel="up">Emacs Octave Support</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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