What are monoids and how to use them - Scala tutorial

Jakub Kozłowski introduces the Monoid and Semigroup type classes in Scala, explaining their rules and demonstrating common use cases.

This video will introduce you to the Monoid and Semigroup type classes, their powers and rules that they have to obey. You'll see examples of common instances of these type classes as well as some more interesting ones, like the Map monoid. You'll also find out why a single type could have more than one lawful instance of the Monoid type class. Table of contents: 0:00 - Introduction 0:50 - Definitions of Semigroup and Monoid 5:14 - Example: adding Integers 6:30 - Example: concatenating Strings 7:04 - Example: List monoid 8:31 - Alternative monoids: Product monoid for Int 10:28 - combineAll 11:38 - foldMap 13:35 - More advanced example: Map monoid (accumulating lists of values) 16:28 - Map monoid: grouping list elements by size 17:34 - Map monoid: counting occurences of elements in list 17:58 - Recap: what we learned 18:28 - Sneak peek of the Monoids and Semigroups libraries Read the code: github.com/kubukoz/videos/tree/master/monoids Previous videos: Traverse - youtube.com/watch?v=CSErp1mZodM Resource - youtube.com/watch?v=m9cu4xUvrUs Bracket - youtube.com/watch?v=vsJz-fdEsd4 Blocker - youtube.com/watch?v=v__IRT-QkwY Learn more about: - Monoid: typelevel.org/cats/typeclasses/monoid.html - Monoids beyond monoids - another talk by my friend Luka (Monoids, Monoids, Monoids): youtube.com/watch?v=DJyhWAwmGqE - monoids/semigroups libraries: github.com/ChristopherDavenport/monoids, github.com/ChristopherDavenport/semigroups - Monoids: Theme and Variations (Functional Pearl): repository.upenn.edu/cgi/viewcontent.cgi?article=1773&contex…