Just reinvented OOP

Learning
7

Wow! And to think I was thinking of asking the OCaml devs to implement it like F# did! :smiley:

This reminds me, I once cooked up this usage with lenses:

#require "lens.ppx_deriving";;

module Address = struct
  type t = { street : string; city : string }
  [@@deriving lens]
end

module Person = struct
  type t = { id : string; name : string; address : Address.t }
  [@@deriving lens]
end

let ( /: ) first second = Lens.compose second first
let ( .:[] ) obj lens = lens.Lens.get obj
let ( .:[]<- ) obj lens value = lens.Lens.set value obj

let bob = {
  Person.id = "1";
  name = "Bob";
  address = {
    Address.street = "1 Way St";
    city = "Cityville";
  };
}

let bob2 = bob.:[Person.address /: Address.street] <- "Rodeo Dr"

==>

val bob2 : Person.t = {
  Person.id = "1";
  name = "Bob";
  address = {
    Address.street = "Rodeo Dr";
    city = "Cityville";
  };
}

EDIT: with a little difflist magic, this could probably become just:

let bob2 = bob.:[[Person.address; Address.street]] <- "Rodeo Dr"
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