question: flatMap/chain and iterables about list HOT 3 CLOSED

I think what your trying to do is reuse a classical OOP collection type, when what you might want is a functional type, e.g.:
https://github.com/fantasyland/fantasy-land#chain

interface Chain {
  // unfortunately, there's a lack of consensus on `chain` vs `flatMap` still...
  flatMap() {}
  chain() {} // same as above
  ap() {}
}
function flatMap<A>(f: (a:A) => Chain<B>, List<A>): List<B>

although I think most libs I've seend tend to give up and just:

function flatMap<A>(f: (a:A) => List<B>, List<A>): List<B>

from list.

yes good point, what did fantasyland decide, and they decided like list and the current prelude.ts (and unlike scala & immutablejs), it's clearly written:

• f must return a value of the same Chain

(f being the callback which is passed in to flatMap/chain)

on the one hand this accepting an Iterable is 'handy', on the other hand it feels a little like Promise.then which mixes up map & flatMap in a single 'then' function. From that point of view the current behavior is better. Still thinking about it though ;)

from list.

Closing. List has its system and obviously doesn't intend to change. I'm also not going to change it for prelude.ts.

from list.