GNU APL mode for Emacs
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Latest commit d79e519 Aug 17, 2017 @lokedhs lokedhs Added missing license
This fixes #23

Emacs mode for GNU APL

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Installing gnu-apl-mode

To install, add the following to your init.el:

(add-to-list 'load-path "~/path-to/gnu-apl-mode")
(require 'gnu-apl-mode)

You can then start the APL interaction using M-x gnu-apl.

GNU APL version requirements

This package requires certain features of GNU APL that was implemented as of version 1.2. In partciular, it takes advantage of a command line option called --emacs which enables certain features that are used by this mode. If your version of GNU APL is too old, you will get an error message saying that the --emacs flag is not understood.

Native code dependencies

This application contains a native part that is compiled into a shared library that is loaded by GNU APL. The source code for this library can be found in the directory native.

GNU APL ships with this library, but if you are using a newer version of this Emacs mode, it may cause compatibility problems between the native module and the Emacs Lisp code. If this happens, you need to compile the module yourself and install it in the lib/apl directory where GNU APL is installed.


This mode provides two different ways to input APL characters. The first is part of the mode itself, and implements the full GNU APL keymap, when the "super" key is active.

If your keyboard does not have a super key (I highly recommend that you map one, for example the otherwise useless windows key), you can also use the APL-Z mode. Simply press C-\ and choose APL-Z. This will provide the same keymap, but prefixed by ".". Pressing dot twice will output a dot on its own.

Keyboard help

By default, the keyboard help buffer is opened whenever the GNU APL interactive mode is started. If you do not want this behaviour, set the variable gnu-apl-show-keymap-on-startup to nil. This value can be customised using M-x customize-variable.


Some operating systems (in particular, Fedora) does not ship with fonts that contain all the nescessary APL symbols. One free font that contains all symbols and also looks good is GNU Free Mono. It can be downloaded here:

Configuring APL font

Usually, one wants to use a different font for APL buffers. This mode includes a face called gnu-apl-default which is used in various places, such as the help buffers. However, it's not currently enabled by default in the interactive session, nor in APL buffers.

If you want to enable this, add the following to your ~/.emacs.d/init.el:

(defun em-gnu-apl-init ()
  (setq buffer-face-mode-face 'gnu-apl-default)

(add-hook 'gnu-apl-interactive-mode-hook 'em-gnu-apl-init)
(add-hook 'gnu-apl-mode-hook 'em-gnu-apl-init)

This enables buffer-face-mode with the chosen font when an APL buffer is opened.

This may be changed to be the default in a future version.