scala-collections

I merged a scala Set of scala Map s using a generic function def mergeMaps[A, B](ms: Set[Map[A, B]])(f: (B, B) => B): Map[A, B] = (Map[A, B]() /: (for (m <- ms; kv <- m) yield kv)) { (a, kv) => a + (if (a.contains(kv._1)) kv._1 -> f(a(kv._1), kv._2) else kv) } This handles the case when there is a clash of same keys. However, I wanted to do it with Java collections in Scala Code. I researched a bit and came across JavaConversions . I imported it and wrote this def mergeMaps[A, B](ms: Set[Map[A, B]])(f: (B, B) => B): Map[A, B] = (new util.HashMap[A, B] /: (for (m <- ms; kv <- m) yield kv)) {

I have a Array of Strings scala> tokens res34: Array[String] = Array(The, value, of, your, profile, is, 234.2., You, have, potential, to, gain, 8.3, more.) Here each of comma separated value is a String. I want to extract numbers from this i.e. my output should be result = (234.2, 8.3) & it should be mutable so that I can read from another array and append values What data structure should I use to achieve this? Consider import scala.util._ tokens.flatMap(s => Try( s.split("\\W+").mkString(".").toDouble ).toOption) where we tokenize further each array string into words and append them by a dot

I have 2 case classes case class First(firstId: Long, pt: Long, vt: Long) case class Second(secondId: Int, vt: Long, a: Long, b: Long, c: Long, d: Long) I have one collection (data:Seq[First]). There is one function which transforms this sequence to another Seq[Second] after applying groupBy and one future operation. getFutureInt is some function returns Future[Int] val output: Future[Seq[Second]] = Future.sequence(data.groupBy(d => (d.vt, getFutureInt(d.firstId))).map {case(k, v) => k._2.map { si => Second(si, k._1, v.minBy(_.pt).pt, v.maxBy(_.pt).pt, v.minBy(_.pt).pt, v.maxBy(_.pt).pt)}}

How do we split list in scala based on difference between neighbouring elements. For example given List(1,3,6,10,12,14) and difference 3, the function would return List(List(1,3),List(6),List(10,12,14)). Can we user foldLeft to do that? I was trying to create a function def splitDiff(list:List[Int],diff:Int) = def func(list:List[List[Int]],m:Int):List[List[Int]] = //compare with last element list.foldLeft(List(List(0))).foldLeft(func) But the inner function seems difficult? Any help? Hmm, I have a solution, but I suspect one can do better: (test.head :: test).sliding(2).toList.map( (pair: List

I have seen a similar post here here which is giving a single key-value pair which has maximum value in the entire Map. But I would like to get List of pairs which has maximum value(maximum value is same for many pairs). Ex : Map(1 -> 7, 2 -> 1, 4 -> 7, 3 -> 2) Expected Output : List(1 -> 7, 4 -> 7) This ( Map(1 -> 7, 2 -> 1, 4 -> 7, 3 -> 2).maxBy(x => x._2) ) will give only first occurrence 1 -> 7 Using map.filter(_._2 == map.values.max) will do the trick. val maxValue = map.values.max map.filter(_._2 == maxValue).toList 来源： https://stackoverflow.com/questions/49792228/getting-all-key-value

The accepted answer to " How to convert a Some(“ ”) to None in one-line? " took the form: def convert(x: Option[String]) : Option[String] = x.map(_.trim()).filterNot(_.isEmpty()) My problem is that I can't figure out how to find by what means the collection returned by filterNot is converted to an Option. I looked at the Scaladoc for Option constructors, Option Object, Predef, Seq, and Seq Object. I figure there's probably an implicit somewhere, but how does one go about finding it? In scaladoc, you can click the "by inheritance" ordering button (it appears just above the methods description).

I want to create a set of integers called IntSet . IntSet is identical to Set[Int] in every way except that its toString function prints the elements as comma-delimited (the same as if you called mkString(",") ), and it has a constructor that takes a Traversable of integers. What is the simplest way to do this? > IntSet((1 to 3)).toString 1,2,3 I'd think there would be some one-line way to do this, but I've been fiddling around with implicit functions and extending HashSet and I can't figure it out. The trick is to use a proxy object. Eastsun has the answer below. Here's a slightly different