A tutorial for Catamorphism and Paramorphism — Recursion schemes are a way of abstracting away recursion. Some have argued that functional programming without recursion schemes is equivalent to imperative programming without for loops, but rather with goto statements. Just as using while and for loops rather than goto brings structure and harmony to imperative control flow, the…

A tutorial on taking the symbolic derivative of a regular expression and an introduction to some Haskell syntax — Symbolic derivatives are used to find the leaking of security keys in emails and for analysing AWS access policies to avoid the accidental exposure of private data —…

A tutorial on adding Memoization, Smart Constructors, Simplification Rules and Extra Operators to the Derivatives for Regular Expression algorithm — In the previous post, we explained what a derivative of a regular expression is, using Pac-Man. In this post, we are going to use Ragas from Indian classic music as an example, to explain how to extend derivatives: with new operators, with simplification rules, smart constructors and memoization as an…

A tutorial explaining the functional regular expression matching algorithm — Eating red cherries gives you the ability to eat blue ghosts. The idea that derivatives can be used to create a regular expression matching algorithm is almost as ridiculous. Let me explain how this algorithm works and how it relates to Pac-Man. In 1964, Brzozowski published the first paper about…

I remember when I was learning Go and typing panic("unreachable") for the first time and not understanding why the type system didn’t know what I knew, that I have covered all the cases and unreachable is unnecessary. Years later I learned that my instinct was right, lots of type systems…

Why? — Monads are all about function composition and hiding the tedious part of it. After 7 years of being a Go programmer, typing if err != nil can become quite tedious. Every time I type if err != …