Does Scala have a version of Rubys' each_slice from the Array class?
+10
A:
Scala 2.8 has grouped that will chunk the data in blocks of size n (which can be used to achieve each_slice functionality):
scala> val a = Array(1,2,3,4,5,6)
a: Array[Int] = Array(1, 2, 3, 4, 5, 6)
scala> a.grouped(2).foreach(i => println(i.reduceLeft(_ + _)) )
3
7
11
There isn't anything that will work out of the box in 2.7.x as far as I recall, but it's pretty easy to build up from take(n) and drop(n) from RandomAccessSeq:
def foreach_slice[A](s: RandomAccessSeq[A], n: Int)(f:RandomAccessSeq[A]=>Unit) {
if (s.length <= n) f(s)
else {
f(s.take(n))
foreach_slice(s.drop(n),n)(f)
}
}
scala> val a = Array(1,2,3,4,5,6)
a: Array[Int] = Array(1, 2, 3, 4, 5, 6)
scala> foreach_slice(a,2)(i => println(i.reduceLeft(_ + _)) )
3
7
11
Rex Kerr
2010-03-16 16:37:29
It would be better to create an `Array` wrapper class, which used the original `Array` as the back-end while presently only a slice of it. An implicit `eachSlice` method could then be added to `Array`, returning a `List[ArraySlice]`. Don't you want to have a go at it in your answer? :-) I can't give you more votes, but I'd admire you. :-) :-)
Daniel
2010-03-16 18:19:22
@Daniel: Hahaha--yes that would be better (faster), but if it's not going in a library somewhere (and why would it since we already have `grouped` in 2.8?), I think I'll leave it as an exercise for the reader.
Rex Kerr
2010-03-16 18:37:12
It would work better for in-place algorithms. You can always submit it for enhancement to Scala. Better sign up the contributor form first, though. I'd like to see such an option available.
Daniel
2010-03-16 19:23:32
Maybe I will after @specialized is pushed through the library a bit more than it is now. Otherwise the boxing/unboxing overhead will swamp everything for primitive types anyway.
Rex Kerr
2010-03-17 08:35:56
+6
A:
Tested with Scala 2.8:
scala> (1 to 10).grouped(3).foreach(println(_))
IndexedSeq(1, 2, 3)
IndexedSeq(4, 5, 6)
IndexedSeq(7, 8, 9)
IndexedSeq(10)
retronym
2010-03-16 16:37:45