Scala not a member of Any - scala

Question

def interpolate(l:List[Tuple2[String,String]]) : List[Tuple2[java.util.Date, Long]] = {
val mapped : List[Tuple2[java.util.Date, Long]] = l.map(item => (format.parse(item._1), item._2.toLong ) )
val results = ListBuffer[Tuple2[java.util.Date, Long]]()
val last : Option[Tuple2[java.util.Date, Long]] = None
mapped.foreach( item =>
if(!last.isEmpty) {
val daysItem = item._1.getTime() / 1000 / 60 / 60 / 24
val daysLast = last.get._1.getTime() / 1000 / 60 / 60 / 24
if( daysItem - daysLast > 1 ) {
val slope = (item._2 - last.get._2) / (daysItem - daysLast)
val days = daysLast until daysItem
val missingChunk : List[Tuple2[java.util.Date, Long]] = days.map( day => (new Date(day * 24 * 60 * 60 * 1000), slope * day)).toList
results ++= missingChunk
}
}
//results += item
last = Some(item)
)
results.toList
}
Error:
<console>:45: error: value last is not a member of Any
possible cause: maybe a semicolon is missing before `value last'?
last = Some(item)
^

Answer 1

There are 2 problems here:
1) multiple statements needs {...} brackets:
from
mapped.foreach((item: (Date, Long)) => item
XXX // OK
YYY // NO
)
to
mapped.foreach { (item: (Date, Long)) => item
XXX // OK
YYY // OK
}
2) val can't be reassigned:
from
val last: Option[Tuple2[java.util.Date, Long]] = None
to
var last: Option[Tuple2[java.util.Date, Long]] = None
Refactor #1
I would try to avoid using var. It seems that with this condition if (last.isDefined) probably we are trying to zip the list with itself:
scala> val l = List(1, 2, 3, 4, 5)
scala> l.zip(l.tail)
List[(Int, Int)] = List((1,2), (2,3), (3,4), (4,5))
Refactoring your example:
import java.util.Date
def interpolate(l: List[(String, String)]): List[(Date, Long)] = {
val mapped: List[(Date, Long)] = l.map(item => (format.parse(item._1), item._2.toLong))
val results = ListBuffer[(Date, Long)]()
mapped.zip(mapped.tail).foreach { case ((lastDate, lastLong), (itemDate, itemLong)) =>
val daysItem = itemDate.getTime / 1000 / 60 / 60 / 24
val daysLast = lastDate.getTime / 1000 / 60 / 60 / 24
if (daysItem - daysLast > 1) {
val slope = (itemLong - lastLong) / (daysItem - daysLast)
val days = daysLast until daysItem
val missingChunk: List[(Date, Long)] = days.map(day => (new Date(day * 24 * 60 * 60 * 1000), slope * day)).toList
results ++= missingChunk
}
}
results.toList
}
Refactor #2
ListBuffer is a mutable collection. In our scenario it seems we are trying to flatten the missingChunks.
Keep refactoring:
def interpolate(l: List[(String, String)]): List[(Date, Long)] = {
val mapped: List[(Date, Long)] = l.map(item => (format.parse(item._1), item._2.toLong))
val missingChunks = mapped.zip(mapped.tail).map { case ((lastDate, lastLong), (itemDate, itemLong)) =>
val daysItem = itemDate.getTime / 1000 / 60 / 60 / 24
val daysLast = lastDate.getTime / 1000 / 60 / 60 / 24
if (daysItem - daysLast > 1) {
val slope = (itemLong - lastLong) / (daysItem - daysLast)
val days = daysLast until daysItem
days.map(day => (new Date(day * 24 * 60 * 60 * 1000), slope * day)).toList
} else List.empty[(Date, Long)]
}
missingChunks.flatten
}