ELODIN

Why named Elodin?

Because he's the master namer, in the Kingskiller chronicles. This project emerged as the side effect of another one called Kvothe. So that's why

Why Elodin?

There are two main purposes

1. Fun
2. Workflows

I used to work for a company called Kiwibot. They do deliveries, and a delivery has a very complex life cycle. In this company, the life cycle was not clear... why? Because the code that described it lived among many projects, and even in each project, it was all scattered around.

So I started thinking... how can I define workflows as code? And I honestly didn't check for existing solutions.

Anyway, what came to mind (given I have a small grasp on continuations and monads), was to define a monad like this (using scala notation):

trait JobOp[+V]
sealed trait Workflow[+A]
case class Job[+V,+A](op:JobOp[V],cont: V=> Workflow[A]) extends Workflow[A]
case class Result[+A](value:A) extends Workflow[A]

def job[T](op:JobOp[T]): Workflow[T] = Job[T,T](op,v=>Result(v))

I can flatMap this structure like this

sealed trait Workflow[+A]{
  def flatMap[B](f: A => Workflow[B]):Workflow[B]
}
case class Job[+V,+A](op:JobOp[V],cont: V=> Workflow[A]) extends Workflow[A] {
  override def flatMap[B](f:  A => Workflow[B]) = {
    Job[V,B](op,{v=>
      cont(v).flatMap(f)
    })
  }
}
case class Result[+T](value:T) extends Workflow[T] {
  override def flatMap[B](f:  T => Workflow[B])  = f(value)
}

Of course, error handling is missing in this structure, but extending it to have one error channel is pretty easy. Anyway, in order to have a workflow be able to be described like this I'd need to be able to persist a Workflow in disk. Most specifically, persist a Job. And to achieve that, I need to be able to serialize JobOb (easy peasy) and the continuation... which is a lambda. And that's it. It all comes down to serializing lambdas. Which I just couldn't do in any language I knew. (And maybe I did a poor research), so that's why I started a quest to define a language in which lambdas are natively serializable.

Also, I've always wished there was something like Javascript (untyped), but pure.