Missing "join" method on ADTs

Based on my understanding of many of the ADTs, as described here, I think crocks is missing join.

Here is a simplified use case (I realize I could create this function with more of the functional building-blocks Crocks supplies):

// { } -> String -> Either(Error String, a)
const getData = payload => {
  return field => {
    const data = payload[field]

    // hmmm..
    if (!data) {
      return Left(new Error(`Cannot get field "${data}"`))
    } else {
      return Right(data)
    }
  }
}

const result = Either(
  getData({ 10: 100, 'dogs': 'cats' })
)
.ap(Right('dogs'))

console.log(result)
// Right Right 'cats'

The problem is that the result is a Right inside a Right.

I’d like to be able to do this:

const result = Either(
  getData({ 10: 100, 'dogs': 'cats' })
)
.ap(Right('dogs'))
.join()

console.log(result)
// Right 'cats'

Am I missing something? Is there a different way to use ap that wouldn’t create nested types?

[karthikiyengar]

I have strong memories of missing this function, and this looks useful for sure. Since we’re prefixing m to most array-colliding functions like mconcat, mreduce et al, we could even consider mjoin for consistency’s sake? I can chalk this out if we’re in agreement.

[mrhubbs]

Hi @evilsoft. Yes, that joinM will be very helpful to me. Thanks a lot!

Here are some random - probably not mathematically sound - brainstorm ideas:

• unbox
• unNest
• unlade
• uncrate
• merge
• meld
• smoosh
• squash
• fuse
• melt

On a different note, I wanted to say earlier that I’m really enjoying this library. I tried a few other functional libraries after reading this book and they felt rather abstruse. Things are really clicking for me with crocks. Thanks a lot!