Hey everyone! This is a multi-layered question and I’ll try my best to try and phrase it cleanly. As an abstract use case I want to have a function that is adjustable in its behaviour by a caller by passing in an optional function (think Map.merge/3). This function is used to determine what my fun…

This is a known problem in functional languages. How to make a recursive anonymous function? Even something as simple as factorial is hard to write: fac = fn(0) -> 1 (n) -> fac.(n-1) * n end ** (CompileError) iex:2: undefined function fac/1 There are topics abou it on Erlang mailing l…

Hmm, can you give an example of the code as you want it to look and what error you get and on what line so we can see what is happening? :slight_smile:

Thanks for sharing this great trick! On the one hand, wished I could have come up with it myself (as I did something like it) but at the same time it’s genius. Had to adapt it a bit as Map.merge/3 expects a function with arity 3. If anyone is interested, this is the commit . Thanks a ton once again…

That style is called the Y-Combinator. There are many kinds of combinators, should look them up. :slight_smile:

Thanks! Definitely still need to brush up my FP (only dabbled in Clojure, LISP and Scala a bit before) which is why Elixir is so great to pick up and learn as I can expand my mind on FP, distributed systems/OTP and many other great concepts. To my shame, before I mistook “Y combinator” for the gene…

[image] PragTob: A bit OT, but if you have some good resource to share (book or web) for learning about “ALL THE COMBINATORS” I’d appreciate it. Maybe I should dig out Land of LISP again… No need for lisp, just normal functional stuff. :slight_smile: I usually just point people to the wikip…

Here’s a great resource to learn about combinators in general, if Ruby as a sample language works for you: Kestrels, Quirky Birds, and Hopeless Egocentricity

[image] gregvaughn: Here’s a great resource to learn about combinators in general, if Ruby as a sample language works for you: http://combinators.info/ That is fascinating. Ruby uses combinators everywhere. Also, wtf?!? [1,2,3,3,4,5].uniq! => [1,2,3,4,5] [1,2,3,4,5].uniq! => nil Uh… …

I’m not sure what static typing has to do with this situation. I think of that wtf as a mutability issue. If you use the non-bang version of uniq you’ll find the result less confusing. I’ve found myself avoiding bang methods in Ruby more and more as my experience grows. irb(main):001:0> a = [1,2,3,…

[image] gregvaughn: I’m not sure what static typing has to do with this situation. I think of that wtf as a mutability issue. If you use the non-bang version of uniq you’ll find the result less confusing. I’ve found myself avoiding bang methods in Ruby more and more as my experience grows. I …

haha yeah the return values of bang methods in ruby are a bad surprise indeed.. this also leads to the fact that you can not safely chain them. I mean, you can chain them if they always modify something and return something but once when they don’t… BOOM. One of the very unintuitive parts. I hope t…

User defined function, recursion and passing self along

Questions & Help Questions

sawthinkar June 17, 2018, 1:21pm 17

Ah, the link seems broken …