λ: folktale data.task - apply an unknown number of Tasks

Question

I am wanting to convert a list of id's into a list of Tasks, and run them concurrently, similar to Promise.all. I am aware of applicatives, but I want to apply an unknown number of tasks so I don't believe that will be the best approach.

Say I have a Task that contains an array of Task's.

Task.of([Task.of(1), Task.of(2)])

Is there anyway to fold the tasks down into a single task that will run them all, or is there a better way that I can handle the data transformation.

The snippet has data.Task included that you can copy if you want to provide an example.

http://folktalegithubio.readthedocs.io/en/latest/api/data/task/

// Task([Task])
Task.of([0, 1, 2])
  .map(t => t.map(Task.of))
  .fork(console.error, console.log)

<script src="https://codepen.io/synthet1c/pen/bWOZEM.js"></script>

@Bergi, I have added a link to the library (folktale data.task) — synthet1c, May 23 '17 at 11:54
Please avoid editing answers directly into the question. Let the answer stay in the answer. — , May 23 '17 at 13:29

score 1 · Accepted Answer · answered May 23 '17 at 12:26

control.async.parallel is exactly what you are looking for.

I am aware of applicatives, but I want to apply an unknown number of tasks so I don't believe that will be the best approach.

That shouldn't hold you back, arrays are traversable and sequenceA would do exactly what you wanted (though quite inefficiently). If it was implemented in folktale, which doesn't feature lists or even a control.applicative.

control.monad.sequence should have been working the same as the applicative sequence, but unnecessarily uses chain instead of ap. And data.task is problematic anyway in that ap is not derivable from chain with the same semantics.

thanks for your help. control.async.parallel is perfect. – synthet1c May 23 '17 at 13:21 — synthet1c, May 23 '17 at 13:21

λ: folktale data.task - apply an unknown number of Tasks

1 Answers1