What's the new name for map2 in Scalaz 7?

Question

Jordan West in this presentation from Scalamachine clearly speaks about map2 function. Turns out the function was available in Scalaz 6 but I can't find it or any equivalent in Scalaz 7.

E.g. I would like to be able to run this code:

List(Some(1), Some(2)).map2(_ + 1)

and get as a result

List(Some(2), Some(3))

Where can I find this function in Scalaz 7?

EDIT: Ideally, I would like to be able to execute any function f: A => B on l: List[Option[A]]

l.map2(f)

And get List[Option[B]] with the intuitive semantics.

Possible duplicate of [How to simplify nested map calls?](http://stackoverflow.com/questions/31284131/how-to-simplify-nested-map-calls) — ZhekaKozlov, Oct 01 '15 at 08:29

score 0 · Answer 1 · answered Sep 30 '15 at 22:20

You can use the applicative syntax instead:

scala> List(Some(1), Some(2)) <*> List((x:Option[Int]) => x |+| Some(1))
res0: List[Option[Int]] = List(Some(2), Some(3))

Scalaz 7 is a different beast compared to Scalaz 6.

Filippo Vitale · Answer 2 · 2015-10-01T05:50:40.010

-1

I haven't found map2 in scalaz 7 and the applicative approach by @I.K. is the most similar I could think. However in this situation where the "shape of the list" doesn't change, I would map and mappend:

List(1.some, 2.some) map (_ |+| 1.some)
res: List[Option[Int]] = List(Some(2), Some(3))

Of course if the default operation assigned to the type is not the desired one, then I would use an exiting Tag from scalaz or a custom implicit.

EDIT

I have just noticed your answer: the other-way-round expected result could be achieved using traverse

List(1.some, 2.some, 3.some) traverseU (_ |+| 1.some)
Some(List(2, 3, 4))

edited Oct 01 '15 at 05:50

answered Oct 01 '15 at 04:55

Filippo Vitale

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Yeah, this is fun but it's not going to work for `List[Option[S]]` where `S` doesn't form a semigroup, right ? – mjaskowski Oct 01 '15 at 07:24
That is correct, if `S` doesn't form a `semigroup` , `Option[S]` doesn't too – Filippo Vitale Oct 04 '15 at 00:17
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`Please consider adding a comment if you think this response can be improved` – Filippo Vitale Oct 04 '15 at 00:22

mjaskowski · Accepted Answer · 2015-10-01T07:33:38.123

-2

Ok, there does not seem to exist such function in Scalaz 7 but there is a nice way around using Monad Transformers:

OptionT[List, Int](List(Some(1), Some(2))).map(_ + 1).run

// List(Some(2), Some(3))

or in the case of l: List[Option[A]]

OptionT[List, A](l).map(f).run

edited Oct 01 '15 at 07:33

answered Sep 30 '15 at 21:22

mjaskowski

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What's the new name for map2 in Scalaz 7?

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