### Warning! Reference to Haskell-like FP abstractions ahead. If you are not interested in this kind of content, please skip reading.
`Task` could be seen as an instance of `Applicative` typeclass, and `map2` function could be implementation of `liftA2` function type. In general, `Applicative` describes combining independent computations, so in case of `Task` that would mean running asynchronous processes in parallel. For example [Task from the Monix scala library](https://monix.io/docs/2x/eval/task.html#the-applicative-zip2-zip3--zip6) is an instance of `Applicative`, and it’s function family zipMapN have parallel semantics.
I believe parallel semantics of `Task.map2` function would be more inline with similar abstractions in FP community.
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### Author:  [@Brian\_Carroll](https://discourse.elm-lang.org/u/Brian_Carroll)
#### Post date: [November 7, 2018, 3:23pm UTC](https://discourse.elm-lang.org/t/task-map2-and-independent-asynchronous-operations/2471/2 "2018-11-07T15:23:26Z")
If you look at the source code for `Task.map2` you’ll see that it’s built on top of `Task.andThen`, which is known as the monadic `bind` or `>>=` in Haskell.
So it already _is_ an applicative. It’s just that the semantics of `andThen` are sequential.
Elm does have monads and applicatives but tends to focus on how to use individual instances of those rather than pushing people to learn the full general concept before starting to get things done. An applicative in Elm is “a type that has `map2`, `map3` etc.”
However `Cmd.batch` doesn’t have sequential semantics so you can use that instead.
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### Author:  [@evancz](https://discourse.elm-lang.org/u/evancz)
#### Post date: [November 7, 2018, 3:30pm UTC](https://discourse.elm-lang.org/t/task-map2-and-independent-asynchronous-operations/2471/3 "2018-11-07T15:30:50Z")
> [@minedeljkovic](#):
>
> I believe parallel semantics of `Task.map2` function would be more inline with similar abstractions in FP community.
Task is roughly equivalent to `IO` in Haskell. Looking at the `IO` instance that defines `liftA2` [here](http://hackage.haskell.org/package/base-4.12.0.0/docs/src/GHC.Base.html#line-1353), you see that it is sequential there as well (`liftA2 = liftM2`). **This is because `Task` and `IO` are both general to all kinds of effects.** Having things go in parallel is often acceptable for HTTP, but it would be quite a problem for reading/writing files.
Adding a way to run tasks in parallel may be nice, but having it be the default for `map2` means that a `Task` will be quite confusing if it is ever used for effects that are not naturally independent. (And even with HTTP, it is not always the case that requests are independent!)
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### Author:  [@Dan\_Abrams](https://discourse.elm-lang.org/u/Dan_Abrams)
#### Post date: [November 7, 2018, 3:36pm UTC](https://discourse.elm-lang.org/t/task-map2-and-independent-asynchronous-operations/2471/4 "2018-11-07T15:36:01Z")
Is there a way to map two independent HTTP requests that are done in parallel, then return a Msg currently? I have a use case for that where they really can and should be parallel, if possible.
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### Author:  [@evancz](https://discourse.elm-lang.org/u/evancz)
#### Post date: [November 7, 2018, 4:02pm UTC](https://discourse.elm-lang.org/t/task-map2-and-independent-asynchronous-operations/2471/5 "2018-11-07T16:02:11Z")
The path for now is to use two different commands.
It is conceivable that there should be an abstraction for HTTP that accounts for parallel requests that should happen together, but it then becomes much more complicated to (1) track errors and (2) track progress. I have tried to do it, but to fully account for these kinds of situations, I have found that it complicates the simple cases quite a bit. My current feeling is that it might want an abstraction of its own, and the starting point there is to get a couple real examples where people feel this might be the best path.
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### Author:  [@system](https://discourse.elm-lang.org/u/system)
#### Post date: [November 17, 2018, 4:02pm UTC](https://discourse.elm-lang.org/t/task-map2-and-independent-asynchronous-operations/2471/6 "2018-11-17T16:02:23Z")
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