Why is the Scala for-loop (and internals) NumericRange restricted to Int size and how to elaborate the functionality?

Question

What's behind the NumericRange Int size restriction on the Scala for-loop comprehension? Is it possible (without to much headache) to extend "for/Seqs" NumericRange to make use of Long (or anything bigger than Int.MaxValue)?

scala>for (i: Long <- 0L to 10000000000) {}

java.lang.IllegalArgumentException: 0 to 10000000000L by 1: "seqs cannot contain more than Int.MaxValue elements."
    at scala.collection.immutable.NumericRange$.count(NumericRange.scala:227)
    at scala.collection.immutable.NumericRange.numRangeElements(NumericRange.scala:53)
    at scala.collection.immutable.NumericRange.length(NumericRange.scala:55)
    at scala.collection.immutable.NumericRange.foreach(NumericRange.scala:73)
    at .<init>(<console>:19)
    at .<clinit>(<console>)
    at .<init>(<console>:11)
    at .<clinit>(<console>)
    at $print(<console>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)
    at scala.tools.nsc.interpreter.IMain$Request$$anonfun$14.apply(IMain.scala:920)
    at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:43)
    at scala.tools.nsc.io.package$$anon$2.run(package.scala:25)
    at java.lang.Thread.run(Thread.java:680)

--
Thanks in advance!

Answer 1

Short answer- it appears to be a "feature" - at least, it's working as designed.

As @drexin pointed out, the implementation of "to" is limited to having an Int range. However...

The problem is that NumericRange[T].count(), .numRangeElements, and .length() returns an Int - regardless of what T is. In this case, it's a NumericRange[Long], where it seems a bit wrong to have count() limited to 31 bits, IMHO.
However...

From browsing Jira issues, this appears to be working as designed. See, e.g., SI-4370. But just to be sure it's been thought out from this perspective, I entered SI-5619.

Answer 2

You cannot count elements as long as their count doesn't fit in Int, because length is declared to return Int, but here is the shortcut: you can create iterators with any actual size, as long as you don't try to count them.

scala> def longRange(first: Long, last: Long) = new Iterator[Long] {
    private var i = first
    def hasNext = i < last
    def next = {val r = i; i += 1; r}
}
longRange: (from: Long, to: Long)java.lang.Object with Iterator[Long]

scala> val lol = longRange(0, Long.MaxValue) map (x => x * x)
lol: Iterator[Long] = non-empty iterator

scala> lol drop 5 take 5 foreach println
25
36
49
64
81