.. index:: lua
.. _lua:

Lua
===

Description
-----------

Lua is a powerful, fast, lightweight scripting language.  It is particularly well-suited to being embedded as part of a compiled program to provide, for example, a user interface and scripting functionality.

User instructions
-----------------

Lua 5.2.4 is installed on all machines.  Other versions of lua, along with libraries and headers, are available via the modules system.  To add it to your environment run (e.g.):

.. code-block:: bash

    $ module load lua/5.3.4

Extensive documentation is available on the `lua website <http://www.lua.org/>`_.  For embedding with Fortran I recommend `AOTUS <https://bitbucket.org/haraldkl/aotus/wiki/Home>`_, the authors of which are very receptive to ideas and contributions.

Source
------

http://www.lua.org/

License
-------

MIT License.

Admin notes
-----------

Very easy and very fast: it's only around 20000 lines of C!

.. code-block:: bash

    wget -O - http://www.lua.org/ftp/lua-5.3.4.tar.gz | tar xvzf -
    cd lua-5.3.4
    make linux -j2
    make test
    make install INSTALL_TOP=/common/debian/9.1/Core/lua/lua-5.3.4

Given the slight incompatibilities between lua versions, I installed the latest versions in the 5.1, 5.2 and 5.3 series.

.. warning::

    We currently don't have any lua modules installed as part of the lua system so the following is just a note work.
    
    lua searches for modules using LUA_PATH (for pure lua modules) and LUA_CPATH (for shared libraries).  If these are set, then they completely override the defaults (rather than extend them).  This means that if an environment module is loaded which sets LUA_PATH and LUA_CPATH, lua can't find any of its built-in libraries!  My solution was to run lua:

    .. code-block:: bash

        $ lua -e "print(package.path, package.cpath)"

    and using the default settings to set LUA_PATH and LUA_CPATH in a custom module file.  Hacky but functional.