add magic documentation

docs/source/index.rst

@@ -32,5 +32,6 @@ This software is licensed under the BSD-3-Clause license. See the LICENSE file f
    :caption: USAGE
    :maxdepth: 2
 
+   magics
    rich_display
    inline_help

docs/source/magics.rst

@@ -0,0 +1,76 @@
+.. Copyright (c) 2017, Johan Mabille, Loic Gouarin and Sylvain Corlay
+
+   Distributed under the terms of the BSD 3-Clause License.
+
+   The full license is in the file LICENSE, distributed with this software.
+
+.. raw:: html
+
+   <style>
+   .rst-content .section>img {
+       border: 1px solid #e1e4e5;
+   }
+   </style>
+
+Magic commands
+==============
+
+Magic commands are widely used in the IPython kernel to perform some actions on a notebook cell. There are defined by the symbol `%` for a line magic and `%%` for a cell magic.
+
+We have started to implement these commands in `xeus-cling` and, in a future release, it will be possible to add your own. In general, the magic command is defined by its name and several options. We use cxxopts_ to manage the options.
+
+For now, we have implemented 2 magic commands
+
+%%file
+------
+
+This magic command copies the content of the cell in a file named `filename`.
+
+.. code::
+
+    %%file [-a] filename
+
+- Example
+
+.. image:: file_magic.png
+
+- Optional argument:
+
++------------+---------------------------------+
+| -a         | append the content to the file. |
++------------+---------------------------------+
+
+%timeit
+-------
+
+Time execution of a line statement (`%timeit`) or of a block of statements (`%%timeit`)
+
+- Usage in line mode
+
+.. code::
+
+    %timeit [-n<N> -r<R> -p<P>] statement
+
+- Usage in cell mode
+
+.. code::
+
+    %%timeit [-n<N> -r<R> -p<P>]
+    statements
+
+- Example
+
+.. image:: timeit_magic.png
+
+- Optional arguments:
+
++------------+---------------------------------------------------------------------------------------------------------+
+| -n         | execute the given statement <N> times in a loop. If this value is not given, a fitting value is chosen. |
++------------+---------------------------------------------------------------------------------------------------------+
+| -r         | repeat the loop iteration <R> times and take the best result. Default: 7                                |
++------------+---------------------------------------------------------------------------------------------------------+
+| -p         | use a precision of <P> digits to display the timing result. Default: 3                                  |
++------------+---------------------------------------------------------------------------------------------------------+
+
+
+.. _cxxopts: https://en.cppreference.com