performance - Why are so few things @specialized in Scala's standard library?

Question

I've searched for the use of @specialized in the source code of the standard library of Scala 2.8.1. It looks like only a handful of traits and classes use this annotation: Function0, Function1, Function2, Tuple1, Tuple2, Product1, Product2, AbstractFunction0, AbstractFunction1, AbstractFunction2.

None of the collection classes are @specialized. Why not? Would this generate too many classes?

This means that using collection classes with primitive types is very inefficient, because there will be a lot of unnecessary boxing and unboxing going on.

What's the most efficient way to have an immutable list or sequence (with IndexedSeq characteristics) of Ints, avoiding boxing and unboxing?

question from:https://stackoverflow.com/questions/5477675/why-are-so-few-things-specialized-in-scalas-standard-library

Answer 1

Specialization has a high cost on the size of classes, so it must be added with careful consideration. In the particular case of collections, I imagine the impact will be huge.

Still, it is an on-going effort -- Scala library has barely started to be specialized.