This reminds me of one of my biggest facepalm-ing moments when I first started using Lisp. I needed to serialise some data to disk, it was all in a list form -

This reminds me of one of my biggest facepalm-ing moments when I first started using Lisp. I needed to serialise some data to disk, it was all in a list form - (list (a b) (c d)) kinda thing. So I thought to use XML format to store it on disk as that's what I had experience with in other languages. I was about halfway through writing the (write-to-xml) function when I realised I could just write the entire lisp expression to the file instead... Not only was it smaller, it had the huge advantage of not needing to parse it back when I wanted to read from disk, I just called the inbuilt (read) function. Thankfully I only wasted an afternoon! That's what really ingrained the whole "data is code, code is data" idea into me. I even went on to write the structure function to each file as well, so that no matter what I did to the data structure down the line, I would still have the actual code needed to understand it. Right next to the data itself. Not only was my code self-documenting, my data was as well ;)