Summary of What is a Monad? - Computerphile

00:00:00 - 00:20:00

In the video, the computer scientist discusses the monad concept and why it may be more appropriate to refer to them as "effects." He points out that there are many monads built into programming languages, and that users don't need to define them themselves.

• 00:00:00 Monads are a concept that was first invented in mathematics in the 1960s, and later rediscovered in computer science in the 1990s. They provide a new way of thinking about programming with effects, and in this video, we're going to look at a simple example of how they can be used to write a function that evaluates simple expressions.
• 00:05:00 The "monad" concept is introduced, and it is explained that a monad is a safe version of the division operator. Safediv is defined, and it takes two integers and returns Maybe an integer if the division may fail. The evaluator is rewritten to use monads, and it is explained that this makes it more like the original program that didn't work.
• 00:10:00 The monad is a type of abstract data type that captures the pattern of multiple occurrences of the same thing. The definition given in the video abstracts this pattern into a definition. This definition can be used to make a simpler program.
• 00:15:00 The video discusses the Maybe monad, a monad built on the idea of effect polymorphism. It covers the idea that monads are a type constructor and two functions that have the type Maybe a -> Maybe b. The point of the video is to emphasize that monads are a powerful way of thinking about programs with effects, and that they support pure programming with effects.
• 00:20:00 The computer scientist discusses the use of the term "monad" and why it may be more appropriate to refer to them as "effects." He points out that there are many monads built into programming languages, and that users don't need to define them themselves.