.. _writing-functions:

############################
  Writing your own functions
############################

**(60 minutes for all the sections below)**

You may recall that I :ref:`previously <rdataframep>` talked about a "wall"
of difficulty you'd hit when working with ``RDataFrame``. Here it is!

So far, I've done my best to assume that you're familiar with no
more than the basics of your programming language. From this point
forward, in order to keep this tutorial to a reasonable length, I have
to assume you know enough to write functions in your chosen language.

Python programmers: You've got it a bit harder, because you're also
going to have to learn something about C++ syntax. 

I'll provide examples from which you can extrapolate. But the burden
of that extrapolation will rest on your shoulders. 

I've broken this topic down into smaller chunks, to hopefully make it
easier to absorb for those who don't have prior experience with
programming.

.. toctree::
   :maxdepth: 1

   Layers.md
   CppFunctions.md
   LambdaExpressions.md
   PythonFunctions.md
   PracticalFunction.md
   
.. figure:: https://imgs.xkcd.com/comics/functional.png
   :width: 30%
   :align: center
   :alt: xkcd functional

   <https://xkcd.com/1270/> by Randall Munroe. Don't worry, I'm not
   going to teach a `functional programming language
   <https://www.infoworld.com/article/3613715/what-is-functional-programming-a-practical-guide.html>`__
   like `LISP <https://www.educba.com/lisp-vs-python/>`__ in this
   tutorial (though I admit I'm tempted).