Splitting an iterator in scala 2.7.5
It looks like there is no partition
method on Iterator
in scala 2.7.5 (there is in 2.8). I would like to have a partition without losing laziness Iterator
, so the next option is not :
itr.toList.partition( someTest(_) )
Can anyone recommend a way to do this without implementing my own method partition
? For example, is there a way to convert Iterator
to lazy-evaluable Stream
?
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Have you tried the method Stream.fromIterator
? It creates a stream containing the elements of the given iterator :).
Example:
val iter = List(1,2,3,4).elements // just a simple iterator
val str = Stream.fromIterator(iter)
str.partition(_ >= 3)
Hope this helps (and this is what you meant).
EDIT: Just an example to show that this is lazy (and memoised - like everyone else Stream
).
scala> val iter = new Iterator[Int] {
| var lst = List(1,2,3,4)
| def hasNext() = !lst.isEmpty
| def next() = { val x = lst.head; println(x); lst = lst.tail; x }
| }
scala> val stream = Stream.fromIterator(iter)
1
stream: Stream[Int] = Stream(1, ?)
scala> stream.partition(_ >= 2)
2
3
4
res1: (Iterable[Int], Iterable[Int]) = (ArrayBuffer(2, 3, 4),ArrayBuffer(1))
scala> stream.partition(_ >= 3)
res2: (Iterable[Int], Iterable[Int]) = (ArrayBuffer(3, 4),ArrayBuffer(1, 2))
NB: left some way out as it was quite verbose.
- Flavi Chipchigan
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