The road less traveled

dakom 2017-08-28 07:21:33 UTC #1

A bit off-topic, but Sodium has been my gateway drug to more functional programming stuff in javascript... I wrote this intro article to using the Either monad from Sanctuary:

Never wrote on medium before and it's a bit of a weird way of teaching, but I learned from the experience so at least there's that :D. Next part will go into more technical detail, this one was more an intro

the-real-blackh 2017-08-28 21:34:12 UTC #2

Nice post! It was my intention in writing the book to get people into functional programming.

dakom 2017-08-29 06:47:29 UTC #3

Well it worked!

One of the problems I have is that it's hard to find good content on this which doesn't require haskell. I'm not totally opposed to learning some haskell, but it's tough for me to retain information unless I really use it, and I don't see myself actually using haskell at the moment.

Do you have any recommended books/videos/resources that teach functional programming but without needing to know haskell (or lisp or scala). I'm comfortable enough reading C,Go,Java,C#,JS/TS,PHP (and well-commented C++ and asm) ... if that helps at all.

the-real-blackh 2017-08-29 21:45:45 UTC #4

Hi David,

Functional programming is really simple - which is actually why it's really good. So, you can do it in any language, but I would use a language with static typing (Typescript rather than Javascript) and with closure syntax (every language now). Haskell is a great language in my opinion, but the learning curve is fairly steep.

Unfortunately to implement monads properly your language needs to have higher order type variables, e.g. You know about List[A] where A is a variable, what about M[A] where M is a type variable that takes one argument A. Not many languages have this other than Haskell. But, monads are fairly advanced functional programming and you don't need them for most things.

As for resources, I don't know much about that, but Manning Publications who were my publisher has been putting out a lot of books about functional programming in non-functional languages recently.

Here are the keys to functional programming:
- Make all your data structures immutable. This is why it's good to have a language that can enforce that. e.g. Java can do it with the final keyword.
- Grab a library with immutable data structures.
- View your code as "what the program is" not "what the program does", e.g. in your blog, you view the code as a sequence of transformations with error handling.
- Write pure functions.
- Keep your I/O on the periphery and away from your logic.
- That's really all there is to it.

It doesn't need to be complicated. Type hackery is not really the core of functional programming. It just adds to it.

Steve

dakom 2017-08-30 08:05:38 UTC #5

Thanks! I'll take a look at the Manning library

Using Sanctuary in js has been a great education, and the community around it has been extremely helpful. I'm not totally aware of the internals but at the end of the day, type checking is strictly enforced and you even get helpful error messages with info about type signatures!

One of the issues I'm struggling with is to get a feel for when to wrap things up in a functor and pass it around like that, and when to use primitive values... how to know what types of common operations are available (e.g. I landed on Sequence() partly from your book and partly by happy accident), etc.

Great advice in general - much appreciated. "View your code as 'what the program is' not 'what the program does'" is a big statement - requires changing the way I think about code in general. Is that something that just sort of happens over time with practice? (I see it happening quite a bit as I'm doing more and more declarative/functional stuff - but wondering if there's a shortcut?)

dakom 2017-08-30 10:56:14 UTC #6

Just bought this book, looks great at a glance: https://www.manning.com/books/functional-programming-in-javascript

If there's a way of telling Manning that you referred it, let me know

the-real-blackh 2017-08-30 21:05:48 UTC #7

David,

Don't worry about referring. I did actually mention that book in my book.

One of the issues I'm struggling with is to get a feel for when to wrap
things up in a functor and pass it around like that, and when to use
primitive values... how to know what types of common operations are
available (e.g. I landed on Sequence() partly from your book and partly
by happy accident), etc.

Yes, in the book I didn't want to get into any of the functor/applicative/monad stuff, but as you've seen, 'sequence' is a very general operation!

Not sure of your exact problem, but the general rule would be just use a plain value until you find an actual need to get more complicated, and then re-factor your existing code. Since the type has changed, the compiler won't let you miss anything.

Steve