scalax-collection

A small library of extension methods for standard scala collections library. Published to maven central.

2.10	2.11	2.12	2.13	3

Collection Examples

An import needed for examples to work:

import com.daodecode.scalax.collection.extensions._

distinctBy

preserving first duplicate

val xs = List(1 -> "one", 1 -> "ten", 2 -> "two", 2 -> "twenty").distinctBy(_._1)
// xs: List[(Int, String)] = List((1, "one"), (2, "two"))

NOTE: Since Scala 2.13 this method is available in standard library

distinctByUsing

or preserving any duplicate you want

val xs = List(1 -> "one", 1 -> "ten", 2 -> "two", 2 -> "twenty").distinctByUsing(_._1, takeFirst = _._2.length > _._2.length)
// xs: List[(Int, String)] = List((1, "ten"), (2, "twenty"))

NOTE: Before 0.3.0 this method was named distinctBy

foldLeftWhile/foldRightWhile

val xs = Iterable(List(1,2,3), List(4,5), List(6,7,8,9)).foldLeftWhile(List.empty[Int])(_.size < 4){ case (acc, l) => acc ++ l }
// xs: List[Int] = List(1, 2, 3, 4, 5)

toCompleteMap

since Scala 2.13 can be seen as equivalent to groupMap(_._1)(_._2)

val cm = List(1 -> "1", 2 -> "2", 1 -> "11").toCompleteMap
// cm: Map[Int, List[String]] = Map(1 -> List("1", "11"), 2 -> List("2"))

mapToMap

can be seen as more efficient replacement for map().toMap combination

val m = List("1" -> "one", "2" -> "two").mapToMap { case (i, s) => i.toInt -> s }
// m: Map[Int, String] = Map(1 -> "one", 2 -> "two")

toMapWithKey

since Scala 2.13 can be seen as equivalent to groupMapReduce(f)(identity)((b,_) => b)

val m = List("1", "2", "1").toMapWithKey(_.toInt)
// m: Map[Int, String] = Map(1 -> "1", 2 -> "2")

toMapWithValue

since Scala 2.13 can be seen as equivalent to groupMapReduce(identity)(f)((b,_) => b)

val m = List("1", "2", "1").toMapWithValue(_.toInt)
// m: Map[String, Int] = Map("1" -> 1, "2" -> 2)

withFrequency

since Scala 2.13 can be seen as equivalent to groupMapReduce(identity)(_ => 1)(_ + _)

val fm = List("a", "b", "c", "a", "b", "d").withFrequency
// fm: Map[String, Int] = Map("a" -> 2, "b" -> 2, "c" -> 1, "d" -> 1)

withFrequencyBy

since Scala 2.13 can be seen as equivalent to groupMapReduce(f)(_ => 1)(_ + _)

val fm = List("ab", "bc", "cd", "ab", "bc", "de").withFrequencyBy(_.head)
// fm: Map[Char, Int] = Map('a' -> 2, 'b' -> 2, 'c' -> 1, 'd' -> 1)

mergedWith

Merges two maps using provided function to merge values for duplicate keys

val merged = Map("1" -> 1, "2" -> 2).mergedWith(Map("1" -> 1, "2" -> 2))(_ + _)
// merged: Map[String, Int] = Map("1" -> 2, "2" -> 4)

minOption/minOptionBy

Finds the smallest element wrapped in Option or None if iterable is empty

val m1 = List.empty[Int].minOption
// m1: Option[Int] = None

val m2 = List(1,2,1).minOptionBy(_ * -1)
// m2: Option[Int] = Some(value = 2)

NOTE: Since Scala 2.13 this is available in standard library

maxOption/maxOptionBy

Finds the largest element wrapped in Option or None if iterable is empty

val m1 = List.empty[Int].maxOption
// m1: Option[Int] = None

val m2 = List(1,2,1).maxOptionBy(_ * -1)
// m2: Option[Int] = Some(value = 1)

NOTE: Since Scala 2.13 this is available in standard library

unzip4/unzip5/unzip6

Similar to unzip and unzip3 from standard library, but for tuples of higher arity (up to 6)

val (ints, strings, chars, doubles) = 
  Iterable(
    (1, "one", '1', 1d),
    (2, "two", '2', 2d),
    (3, "three", '3', 3d),
    (4, "four", '4', 4d)
  ).unzip4
// ints: Iterable[Int] = List(1, 2, 3, 4)
// strings: Iterable[String] = List("one", "two", "three", "four")
// chars: Iterable[Char] = List('1', '2', '3', '4')
// doubles: Iterable[Double] = List(1.0, 2.0, 3.0, 4.0)

Strings Examples

An import needed for examples to work:

import com.daodecode.scalax._

NonEmptyString

NonEmptyString(null)
// res0: Option[String] = None
NonEmptyString("")
// res1: Option[String] = None
NonEmptyString(" a ")
// res2: Option[String] = Some(value = " a ")

(null: String) match {
  case NonEmptyString(_) => "boo" 
  case _ => "works!"
}
// res3: String = "works!"

"" match {
  case NonEmptyString(_) => "boo" 
  case _ => "works!"
}
// res4: String = "works!"

"works!" match {
  case NonEmptyString(s) => s 
  case _ => "boo"
}
// res5: String = "works!"

NonBlankString

NonBlankString(null)
// res6: Option[String] = None
NonBlankString("")
// res7: Option[String] = None
NonBlankString(" \n \r \t ")
// res8: Option[String] = None
NonBlankString(" a ")
// res9: Option[String] = Some(value = " a ")

(null: String) match {
  case NonBlankString(_) => "boo" 
  case _ => "works!"
}
// res10: String = "works!"

"" match {
  case NonBlankString(_) => "boo" 
  case _ => "works!"
}
// res11: String = "works!"

"   \t " match {
  case NonBlankString(_) => "boo" 
  case _ => "works!"
}
// res12: String = "works!"

"works!" match {
  case NonBlankString(s) => s 
  case _ => "boo"
}
// res13: String = "works!"

NonBlankTrimmedString

NonBlankTrimmedString(null)
// res14: Option[String] = None
NonBlankTrimmedString("")
// res15: Option[String] = None
NonBlankTrimmedString(" \n \r \t ")
// res16: Option[String] = None
NonBlankTrimmedString(" a ")
// res17: Option[String] = Some(value = "a")

(null: String) match {
  case NonBlankTrimmedString(_) => "boo" 
  case _ => "works!"
}
// res18: String = "works!"

"" match {
  case NonBlankTrimmedString(_) => "boo" 
  case _ => "works!"
}
// res19: String = "works!"

"   \t " match {
  case NonBlankTrimmedString(_) => "boo" 
  case _ => "works!"
}
// res20: String = "works!"

"  works!\n  " match {
  case NonBlankTrimmedString(s) => s 
  case _ => "boo"
}
// res21: String = "works!"

Latest stable release

sbt

libraryDependencies += "com.daodecode" %% "scalax-collection" % "0.3.2"

maven

set <scala.binary.version> property to scala version you need, like

<properties>
    <scala.binary.version>2.13</scala.binary.version>
</properties>

and then in dependencies add

<dependency>
    <groupId>com.daodecode</groupId>
    <artifactId>scalax-collection_${scala.binary.version}</artifactId>
    <version>0.3.2</version>
</dependency>