What is the meaning of this snippet of code?

Question

I am studying Scala language and I do not understand this piece of code:

for {
  i <- Set(2,3)
  j <- 1 to i
  k <- i to 2 by -1
} yield (j,k)

What does it mean that j is a Range from 1 to i when i is a Set?

`i` isn't a `Set`. It is an element from the set, i.e. `2` or `3`. — jwvh, May 17 '21 at 07:26

score 2 · Accepted Answer · answered May 17 '21 at 08:23

I recommend that you read the Scala documentation about for-comprehension and/or this answer on SO: Confused with the for-comprehension to flatMap/Map transformation

The code you provided is strictly equivalent to the following one:

Set(2,3)
  .flatMap { i => 
    (1 to i).flatMap { j =>
      (i to 2 by -1).map { k =>
        (j,k)
      }
    }
  }

This way, you should see better that i is an "item" from the Set.

1 Answers1