How to create a map with indexed keys in scala?

Question

I'm trying to create a Map with idiomatic Scala with a sequenced key and a value of zero. I was thinking something like this:

(0 to 445) map (_ => _ -> 0).toMap

but that fails the IDE (IDEA) complains with cannot resolve symbol ->

and the compiler complains about missing parameter type

What do I do wrong?

Answer 1

You can only use the placeholder _ once in a function declaration for each argument. What you want is this:

(0 to 445) map (_ -> 0).toMap

or an explicit value like this

(0 to 445) map (x => x -> 0).toMap

Answer 2

Another option you have is to use zipAll:

0.to(445).zipAll(Seq.empty[Int], 0, 0).toMap

or zip:

0.to(445).zip(Seq.fill(445)(0)).toMap

or:

Map.from(0.to(445).map(_ -> 0))

Code run at Scastie.