jasonofthel33t
9 HN recommenders · recommended in 15 months, 2012–2024
1:07:10 · 415K views · Nov 21, 2012
Microsoft's Brian Beckman gives an hour-long, whiteboard-style walk through monads, building from function composition and monoids using school-level math. It is aimed at practicing programmers rather than category theorists.
HN repeatedly recommends it as the clearest and most correct beginner explanation of monads, with several commenters saying it finally made them click.
16 comments from Hacker News
I don't know category theory, so I defer to more knowledgeable people here, but that sounds strange: "Functor it understands how to take doStuff and execute it on the value inside itself, then spit out a new Optional. You don't lose the int-ness or optional-ness." So if I map a function, that takes an int and returns a string over an array of ints, this array stops being a functor? Or is it just a Swift thing? And, as always, I urge people spend an hour of their life and get the explanation of all this from someone who knows the math but still able to explain this in plain English: this video To the best of my limited knowledge, it's all 100% correct.
To be fair, (I think) you don't need to know category theory to successfully apply FP principles and/or use any functional language. I had a great (GREAT) success at using erlang not only not knowing what monad is, but even not knowing about existence of category theory at all, leave aside monads, monoids, functors, etc. You also don't need to know category theory to understand what monad is [0] This video is all you, as a practicing programmer, need to know about monads and it's just 1 hour long. [0] this video
Thats me here too! >.< Yeah the hidden subtext here was my presumption in that suggestion was someone was learning monads in Haskell and has at least a basic understanding of Haskell. Sorry if those papers threw you into the deep end. Monads really were thrown into play due to trying to make a pure functional programming language useful. I found the more mathematical explanation a lot easier than any analogies involving say burritos or pipes etc... At first glance to imperative programmers I will admit all of this just looks like a bunch of navel gazing. I thought the same thing, but once you let go of thinking of computation as a series of steps and at a bit of a higher abstraction this makes a lot more sense. For a more soft introduction to the concepts this channel 9 video is probably a bit better: this video Another option might be to just get the haskell programming from first principles book: [LINK] Does a good job grounding you up to monads and gives copious amounts of reference material. Even though I already knew haskell when I read the book it helped clear up some gaps I didn't know I had. But monads are going to be really weird no matter if all you've ever seen is imperative programming. Despite the fact that you already use them and have probably discovered them without knowing you did. Much like learning stack based programming languages, sometimes the only way up is to climb off the computational hill you're familiar with to learn another way to the other hill side
> and apparently I'm never going to understand Haskell I found this introduction to the concepts of functional programming (functional composition) to be useful: this video Otherwise, it's just a different way of thinking about problems. Instead of building things structurally as an object of objects, and then creating functions that relate, transform, or describe the relationships between the object structures (like taking a pixel object, altering it's x coordinate, and returning the new pixel object with only the x coordinate altered), one has functions that can be composed with other functions to produce more complex object structures. A single base unit with a sequence of functional compositions can describe a very fancy, complex unit, with many fancy, complex characteristics. >> Monads have also been explained with a physical metaphor as assembly lines, where a conveyor belt transports data between functional units that transform it one step at a time.[2] They can also be seen as a functional design pattern to build generic types.[3] [LINK] Otherwise, it's syntax and semantics, which I generally find annoying, but there's always google and books. [LINK]
I've seen the same video before i knew what a monad was, it helped me in understanding the use case of monad and ultimately monad. Monad is just a generalization of that particular use case. Some resources that helped me in understanding monads 1. Brian Beckman: Don't fear the Monad - this video 2. Functors, Applicatives, And Monads In Pictures - [LINK] 3. Three Useful Monads - [LINK] So its been not just one resource but multiple resource before it hit me that it was such a simple concept. So i would suggest to go over them (in order) and also look at other resources (mentioned by others).