emacs.sgml

OTP是开放电信平台的简称

<EM> Example 3: </EM>
</P>

<P>
Here we assume that we have defined a new skeleton named
<C>erlang-skel-example</C>.  The best time to add this skeleton to the
variable <C>erlang-skel</C> is when Erlang mode has been loaded but
before it has been activated.  We define a function that adds two
entries to <C>erlang-skel</C>, the first is <C>()</C> that represent a
divisor in the menu, the second is the entry for the <C>Example</C>
skeleton.  We then add the function to the <C>erlang-load-hook</C>, a
hook that is called when Erlang mode is loaded into Emacs.

<CODE>
(defun my-erlang-skel-hook ()
  (setq erlang-skel
	(append erlang-skel
                '(()
                  ("Example" "example" erlang-skel-example)))))

(add-hook 'erlang-load-hook 'my-erlang-skel-hook)
</CODE>

</SECTION>
</SECTION>
</SECTION>

<!-- CHAPTER -->

<SECTION>

<TITLE>Manual Pages</TITLE>

<P>
The UNIX version of Erlang tools contain a set of manual pages that
can be accessed by the standard UNIX command "man".  The Erlang mode
place a list of all available manual pages in the "Erlang" menu.
</P>

<P>
Unfortunately this feature is not available in the Windows version of
the Erlang editing mode since the Erlang tools are not delivered with
the manual pages.
</P>

<SECTION>
<TITLE> The Menu </TITLE>

<P>
In the Erlang menu a list of all Erlang manual pages can be found.
The menu item "Man Pages".  The sub-menu to this menu item contains a
list of categories, normally "Man - Commands" and "Man - Modules".
Under these is a menu containing the names of the man pages.
Should this menu be to large it is split alphabetically into a number
of sub-menus.
</P>

<P>
The menu item "Man - Function" is capable of finding the man page of a
named Erlang function.  This commands understands the
<C>module:function</C> notation.  This command defaults to the name under
the point.  Should the name not contain a module name the list of
imported modules is searched.
</P>

</SECTION>

<SECTION>
<TITLE>Customization</TITLE>

<P>
The following variables control the manual page feature.
</P>

<LIST>

  <ITEM><C>erlang-man-dirs</C><BR>

<P>
This variable is a list representing the sub-menu to the "Man Pages"
menu item in the Erlang menu.  Each element is a list with three
elements.  The first is the name of the menu, e.g. "Man - Modules" or
"Man - Local Stuff".  The second is the name of a directory.  The
third is a flag that control the interpretation of the directory.
When <C>nil</C> the directory is treated as an absolute path, when
non-<C>nil</C> it is taken as relative to the directory named in the
variable <C>erlang-root-dir</C>.
</P>


  <ITEM><C>erlang-man-max-menu-size</C><BR>

<P>
The maximum number of menu items in a manual page menu.  If the number
of manual pages would be more than this variable the menu will be
split alphabetically into chunks each not larger than the value of
this variable.
</P>

</LIST>

</SECTION>
</SECTION>

<!-- CHAPTER -->

<SECTION>
<TITLE>Tags</TITLE>

<P>
Tags is a standard Emacs package used to record information about
source files in large development projects.  In addition to listing
the files of a project, a tags file normally contains information
about all functions and variables that are defined.  By far, the most
useful command of the tags system is its ability to find the
definition of functions in any file in the project.  However the Tags
system is not limited to this feature, for example, it is possible to
do a text search in all files in a project, or to perform a
project-wide search and replace.
</P>

<SECTION>
<TITLE>Creating a TAGS file</TITLE>

<P>
In order to use the Tags system a file named <C>TAGS</C> must be created.
The file can be seen as a database over all functions, records, and
macros in all files in the project.  The <C>TAGS</C> file can be created
using to different methods for Erlang.  The first is the standard
Emacs utility "etags", the second is by using the Erlang module
<C>tags</C>.
</P>

</SECTION>

<SECTION>
<TITLE>The etags utility</TITLE>
<!-- <TITLE>The <C>etags</C> utility</TITLE> -->

<P>
The <C>etags</C> is a program that is part of the Emacs distribution.  It
is normally executed from a command line, like a unix shell or a DOS
box.
</P>

<P>
The <C>etags</C> program of fairly modern versions of Emacs and XEmacs
has native support for Erlang.  To check if your version does include
this support, issue the command <C>etags --help</C> at a the command
line prompt.  At the end of the help text there is a list of supported
languages.  Unless Erlang is a member of this list I suggest that you
should upgrade to a newer version of Emacs.
</P>

<P>
As seen in the help text -- unless you have not upgraded your Emacs yet
(well, what are you waiting around here for?  Off you go and upgrade!)
-- <C>etags</C> associate the file extensions <C>.erl</C> and
<C>.hrl</C> with Erlang.
</P>

<P>
Basically, the <C>etags</C> utility is runed using the following form:
</P>

<CODE>
    etags file1.erl file2.erl
</CODE>

<P>
This will create a file named <C>TAGS</C> in the current directory.
</P>

<P>
The <C>etags</C> utility can also read a list of files from its standard
input by supplying a single dash in place of the file names.  This
feature is useful when a project consists of a large number of files.
The standard UNIX command <C>find</C> can be used to generate the list of
files, e.g:
</P>

<CODE>
    file . -name "*.[he]rl" -print | etags -
</CODE>

<P>
The above line will create a <C>TAGS</C> file covering all the Erlang
source files in the current directory, and in the subdirectories
below.
</P>

<P>
Please see the GNU Emacs Manual and the etags man page for more info.
</P>


<P>
The code implementing the Erlang support for the <C>etags</C> program has
been donated to the Free Software Foundation by the company Anders
Lindgren Development.
</P>

</SECTION>

<SECTION>
<TITLE>The tags Erlang module</TITLE>
<!-- <TITLE>The <C>tags</C> Erlang module</TITLE> -->

<P>
One of the tools in the Erlang distribution is a module named
<C>tags</C>.  This tool can create a <C>TAGS</C> file from Erlang
source files.
</P>

<P>
The following are examples of useful functions in this module.  Please
see the reference manual on tags for details.
</P>

<LIST>

  <ITEM><C>tags:file('foo.erl').</C><BR>

<P>
Create a <C>TAGS</C> file for the file "foo.erl".
</P>

  <ITEM><C>tags:subdir('src/project/', [{outfile, 'project.TAGS'}]).</C><BR>

<P>
Create a tags file containing all Erlang source files in the directory
<C>"src/project/"</C>.  The option <C>outfile</C> specify the name of
the created <C>TAGS</C> file.
</P>

  <ITEM><C>tags:root([{outdir, 'bar'}]).</C><BR>

<P>
Create a <C>TAGS</C> file of all the Erlang files in the Erlang
distribution.  The <C>TAGS</C> file will be placed in the the directory
<C>bar</C>.
</P>

</LIST>

</SECTION>

<SECTION>
<TITLE>Additional Erlang support</TITLE>

<P>
The standard Tags system has only support for simple names.  The
naming convention <C>module:function</C> used by Erlang is not supported.
</P>

<P>
The Erlang mode supplies an alternative set of Tags functions that is
aware of the format <C>module:function</C>.  When selecting a the
default search string for the commands the name under the point is
first selected.  Should the name not contain a module name the
<C>-import</C> list at the beginning of the buffer is scanned.
</P>

<SECTION>

<TITLE>Limitations</TITLE>

<P>
Currently, the additional Erlang module name support is not compatible
with the <C>etags.el</C> package that is part of XEmacs.
</P>

</SECTION>
</SECTION>

<SECTION>
<TITLE>Useful Tags Commands</TITLE>

<LIST>

  <ITEM><C> M-. </C> (<C>erlang-find-tag</C>)<BR>

<P>
Find a function definition.  The default value is the function name
under the point.  Should the function name lack the module specifier
the <C>-import</C> list is searched for an appropriate candidate.
</P>


  <ITEM><C> C-u M-. </C> (<C>erlang-find-tag</C> with an argument)<BR>

<P>
The <C>find-tag</C> commands place the point on the first occurrence of
a function that match the tag.  This command move the point to the
next match.
</P>


  <ITEM><C> C-x 4 . </C> (<C>erlang-find-tag-other-window</C>)<BR>

<P>
As above, but the new file will be shown in another window in the same
frame.
</P>


  <ITEM><C> C-x 5 . </C> (<C>erlang-find-tag-other-frame</C>)<BR>

<P>
As <C>erlang-find-tag</C> but the new file will be shown in a new frame.
</P>

  <ITEM><C> M-TAB </C> (<C>erlang-complete-tag</C>)<BR>

<P>
This command is used to fill in the end of a partially written
function name.  For example, assume that the point is at the end of
the string <C>a_long</C>, and the Tags file contain the function
<C>a_long_function_name</C>.  By executing this command the string
<C>a_long</C> will be expanded into <C>a_long_function_name</C>.
</P>


  <ITEM><C> M-x tags-search RET </C><BR>

<P>
This command will search through all the files in a project for a
string.  (Actually, it search for a pattern described by a regular
expression.)
</P>


  <ITEM><C> M-, </C> (<C>tags-loop-continue</C>)<BR>

<P>
Move the point to the next search match.
</P>

</LIST>

</SECTION>
</SECTION>

<SECTION>
<TITLE>IMenu</TITLE>

<P>
IMenu is a standard package of GNU Emacs.  With IMenu it is possible
to get a menu in the menu bar containing all the functions in the
buffer.  Erlang mode provides support for Erlang source files.
</P>

<!-- TODO
<P>
Unfortunately the IMenu package is not part of XEmacs.  In the future
Erlang mode might get support for the XEmacs package "funcmenu" that
provides similar support for XEmacs.
</P>
-->

<SECTION>
<TITLE>Starting IMenu</TITLE>

<LIST>

  <ITEM><C> M-x imenu-add-to-menubar RET</C><BR>

<P>
This command will create the IMenu menu containing all the functions
in the current buffer.  The command will ask you for a suitable name
for the menu.
</P>

</LIST>
</SECTION>

<SECTION>
<TITLE>Customization</TITLE>

<P>
See chapter "<SEEALSO MARKER="#customization">Customization</SEEALSO>"
below for a general description on how to customize the Erlang mode.
</P>

<P>
To automatically create the IMenu menu for all Erlang buffers, place
the lines below into the appropriate init file (e.g. ~/.emacs).  The
function <C>my-erlang-imenu-hook</C> will be called each time an
Erlang source file is read.  It will call the
<C>imenu-add-to-menubar</C> function.  The menu will be named
"Functions".
</P>

<CODE>
(add-hook 'erlang-mode-hook 'my-erlang-imenu-hook)

(defun my-erlang-imenu-hook ()
  (if (and window-system (fboundp 'imenu-add-to-menubar))
      (imenu-add-to-menubar "Functions")))
</CODE>

</SECTION>
</SECTION>

<!-- ---------------------------- Inferior Erlang -->

<!-- - CHAPTER -->

<SECTION>
<TITLE>Running Erlang from Emacs</TITLE>

<P>
One of the strengths of Emacs is its ability to start slave processes.
Since Emacs is extendible it is possible let Emacs be a part of a
large application.  For example, Emacs could be used as the user
interface for Erlang applications.
</P>

<P>
The Erlang editing mode provides two simple, yet very useful,
applications.  The first is to start an Erlang shell and use an Emacs
buffer for input and output.  The second is a compile commands that
makes it possible to compile Erlang modules and to locate the lines
containing the compilation errors.
</P>

<P>
The actual communication between Emacs and Erlang can be performed by
different low-level techniques.  The Erlang editing mode provides a
technique called "inferior" processes.  The add on package Erl'em
supplies a technically much more advanced communication technique
known as an Erl'em link.  All the commands that are provided by the
editing mode can use either technique.  However, more advanced
packages will probably need features only provided by the Erl'em
package.
</P>

<SECTION>
<TITLE>Inferior Erlang</TITLE>

<P>
The editing mode is capable of starting a so called "inferior" Erlang
process.  This is a normal subprocess that use one Emacs buffer for
input and output.  The effect is that a command line shell, or an
Erlang shell, can be displayed inside Emacs.
</P>

<P>
The big drawback with an inferior process is that the communication
between Emacs and the process is limited to commands issued at the
command line.  Since this is the interface that is used by the user it
is difficult, to say the least, to write an Emacs application that
communicate with the inferior process.  For example, the
<C>erlang-compile</C> command described in the section "Compilation"
below really stretch the capabilities of the inferior Erlang process.
In fact, should the user have issued a command that would take some
time to complete it is impossible for Emacs to perform the
<C>erlang-compile</C> command.
</P>

</SECTION>


<SECTION>
<TITLE>The Erl'em Link</TITLE>

<P>
The Erl'em package established a low-level communication channel
between Emacs and an Erlang node.  This communication channel can be
used by Emacs to issue several independent Erlang commands, to start
Erlang processes and to open several Erlang IO streams.  It is also
possible for Erlang to call Emacs functions.
</P>

<P>
In short the Erl'em package is designed to be the base of complex
application that is partially implemented in Emacs and partially in
Erlang.
</P>

<P>
It is the hope of the author that the Erl'em link in the future will
be used as the base for porting the user interface of the Erlang
debugger to Emacs.  If this could be possible, Emacs could be used as
an Integrated Debugger Environment (IDE) for Erlang.
</P>

<P>
The structure of the Erl'em link and its programming interface is
described in the text "Erl'em Developers Manual".
</P>

</SECTION>
</SECTION>

<!-- CHAPTER -->

<SECTION>
<TITLE>Erlang Shell</TITLE>

<P>
It is possible to start an Erlang shell inside Emacs.  The shell will
use an Emacs buffer for input and output.  Normal Emacs commands can
be used to edit the command line and to recall lines from the command
line history.
</P>

<P>
The output will never be erased from the buffer so you will never risk
letting important output fall over the top edge of the display.
</P>

<P>
As discussed in the previous chapter there are two low-level