Collection library for Scala Programming Language
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Questions tagged [scala-collections]
1639 questions
0
votes
1 answer
What's the easiest way to circumvent [SI-6976] in scala 2.10 for primitive collection pattern matching?
I have a simple function:
implicit class ArrayView[A](self: Array[A]) {
def filterByType[B <: A: ClassTag]: Array[B] = {
val ctg = implicitly[ClassTag[B]]
val runtimeClazz = ctg.runtimeClass
self.flatMap{
v =>
…
tribbloid
- 4,026
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0
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1 answer
Scala - map a value from a Map to another Map
I've a requirement to map a field in my RDD to another field from another map UserDAO.users I've tried to figure out the mapping here but can't return the username yet. I'm getting this in the updated map when I do a foreach print…
Philip K. Adetiloye
- 3,102
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- 63
0
votes
1 answer
Scala Overloading Issue
If I have a java.util.Map[String,Java.util.Map] for the first call, correct overloaded method is called: toScala(java.util.Map[_,_]). But in the mapValues invocation, function toScala(other:Any) is called. How to avoid this?
I would be calling…
bugs
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- 2
0
votes
1 answer
Scala sum of the arrays contained in an array
I have defined a function that receives an array of arrays. I want to get the sum of all arrays. My question is how to make that sum.
def suma[T](args: WrappedArray[T]*)(implicit n: Numeric[T]) = {
args.transpose.map(_.sum)
}
def sum[T](arr:…
nest
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- 17
0
votes
2 answers
High performance Scala/Java collection needed
I am looking for a Scala (or Java/Guava) collection that supports O(1) access to (and ideally removal of) its minimum element as well as O(log n) insertion and removal of arbitrary elements.
Thoughts?
davidrpugh
- 4,363
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- 46
0
votes
1 answer
Scala 2.10: Convert mutable Map of ListBuffer to readonly datastructure
I am using the following code to traverse directories and adding files to a mutable Map of mutable ListBuffer. The key is the directory name and the values are the list of files under that directory.
def WalkDir(path:String):…
Neel
- 9,913
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- 74
0
votes
2 answers
How do you create a Scala collection of content in a Play template?
I'm sure I'm missing the obvious but is there a way to create a collection of Html objects to pass to a Play template like @(title: String)(content: Seq(Html))? I am trying to dynamically generate a group of tab pages where each Html object is the…
geeforce
- 15
- 3
0
votes
1 answer
How do I modify this library design so that Scala will infer the correct builder implicit argument?
Below I have a simplified version of a library I'm working on. I modeled this after the scala collection library's CanBuildFrom trait, since my requirements are similar. However, I can't quite get it to infer the correct builder to use in all…
Nimrand
- 1,748
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- 29
0
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2 answers
Scala: Creating singleton object by calling constructor
I want to create a singleton object for my application , but i want to initialize it from another object.
For ex :
object A{
val x = 10
val b = B(x)
}
object B(y:Int){
var z = y
}
But this would not work , since object doesnt have constructor.…
Alok
- 1,374
- 3
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- 44
0
votes
0 answers
spark job freeze when started in ParArray
I want to convert a set of time-serial data to Labeledpoint from multiple csv files and save to parquet file. Csv Files are small, usually < 10MiB
When I start it with ParArray, it submit 4 jobs a time and freeze . codes here
val idx =…
skywalkerytx
- 244
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- 14
0
votes
1 answer
Scala data structure for storing multiple variable which can be used in collection.contains or collection.exisits
I have a requirement ,where i have multiple tuples coming in.
For eg: (a1, b1)
(a2, b2)
(a3, b3)
I need to store these values in datastructure and create a collection of these.
Next I will get another tuple as input (an, bn) and i…
Alok
- 1,374
- 3
- 18
- 44
0
votes
1 answer
A (strictly) `Growable` mutable `Seq`
I need a (mutable) Seq that is only Growable. I do not need to update any index or shrink the collection or transform it (or any other form of mutation), Just grow it (+=) and I want to actively protect the collection from other mutations.
The…
Ashkan Kh. Nazary
- 21,844
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- 68
0
votes
1 answer
Scala : How to find types of values inside a scala nested collection
consider the following variables in scala :
val nestedCollection_1 = Array(
"key_1" -> Map("key_11" -> "value_11"),
"key_2" -> Map("key_22" -> "value_22"))
val nestedCollection_2 = Map(
"key_3"-> ["key_33","value_33"],
"key_4"->…
Sriram
- 53
- 7
0
votes
1 answer
Runtime of tail and init on List
if I have the following with ls an instance of scala.collection.immutable.List :
will ls.init make a copy of the first n-1 elements of ls and then
give this copy back thus yielding a runtime of theta of n-1(because of the copy runtime)?
Does…
Simonlbc
- 591
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0
votes
1 answer
Optional tuples to Map in Scala
If I have a List of tuples, I can convert to a map with toMap:
val x = (3 -> 3)
List(x).toMap
and I get
scala.collection.immutable.Map[Int,Int] = Map(3 -> 3)
If I have a List of Optional and try the same I would get an error:
val x = Some(3 ->…
pedrorijo91
- 7,635
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