Why are there no methods toVector (like toList, toArray) in standard collection types?

Question

If we are supposed to use Vector as the default Sequence type, why are there no methods toVector (like toList, toArray) in standard collection types?

In prototyping stage, is it okay to conform all collections to Seq type and use toSeq on all collection-returns (cast everything to Seq)?

Answer 1

Normally you should be more concerned with the interface that the collection implements rather than its concrete type, i.e. you should think in terms of Seq, LinearSeq, and IndexedSeq rather than List, Array, and Vector, which are concrete implementations. So arguably there shouldn't be toList and toArray either, but I guess they're there because they're so fundamental.

The toIndexedSeq method in practice provides you with a Vector, unless a collection overrides this in order to provide a more efficient implementation. You can also make a Vector with Vector() ++ c where c is your collection.

Answer 2

Scala 2.10 will come with a method .to[C[_]] so that you can write .to[List], .to[Array], .to[Vector], or any other compatible C.

Answer 3

Scala 2.10 adds not only .to[Vector], but .toVector, as well:

In TraversableOnce trait inherited by collections and iterators:

abstract def toVector: Vector[A]