Collection type generated by for with yield

When I evaluate a for in Scala, I get an immutable IndexedSeq (a collection with array-like performance characteristics, such as efficient random access):

scala> val s = for (i <- 0 to 9) yield math.random + i
s: scala.collection.immutable.IndexedSeq[Double] = Vector(0.6127056766832756, 1.7137598183155291, ...

Does a for with a yield always return an IndexedSeq, or can it also return some other type of collection class (a LinearSeq, for example)? If开发者_如何学Go it can also return something else, then what determines the return type, and how can I influence it?

I'm using Scala 2.8.0.RC3.

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Thanks michael.kebe for your comment.

This explains how for is translated to operations with map, flatMap, filter and foreach. So my example:

val s = for (i <- 0 to 9) yield math.random + i

is translated to something like this (I'm not sure if it's translated to map or flatMap in this case):

val s = (0 to 9) map { math.random + _ }

The result type of operations like map on collections depends on the collection you call it on. The type of 0 to 9 is a Range.Inclusive:

scala> val d = 0 to 9
d: scala.collection.immutable.Range.Inclusive with scala.collection.immutable.Range.ByOne = Range(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

The result of the map operation on that is an IndexedSeq (because of the builder stuff inside the collections library).

So, to answer my question: the result of a for (...) yield ... depends on what type is inside the parantheses. If I want a List as the result, I could do this:

scala> val s = for (i <- List.range(0, 9)) yield math.random + i
s: List[Double] = List(0.05778968639862214, 1.6758775042995566, ...

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You can always transform a range to a list using toList:

> val s = for (i <- (0 to 9).toList) yield math.random + i
> s  : List[Double]