Why functional programming?

Why do I like functional programming?

For some reason, I really love functional programming. Although my whole career has been involving object oriented programming and the imperative paradigm: Delphi, C#, Java, Ruby etc.

Ever since I met Elixir, something is attracting me to it. The idea of immutability with functions that always return the same output given the same input seems so good.

But overall, I wasn't sure why I was drawn to this.

My 1998 thesis

Then I remembered my 1998 thesis:

ZTrans: A Semi-Automatic Translator from Z to SML