How to split a List[Either[A, B]]

cats either
scala list of either to either of list
scala either
scala either monad
scala cats separate
scala either get right
scala partition list
scala map split

I want to split a List[Either[A, B]] in two lists.

Is there a better way ?

def lefts[A, B](eithers : List[Either[A, B]]) : List[A] = eithers.collect { case Left(l) => l}
def rights[A, B](eithers : List[Either[A, B]]) : List[B] = eithers.collect { case Right(r) => r}

Not sure this is really much neater, but :

scala> def splitEitherList[A,B](el: List[Either[A,B]]) = {
         val (lefts, rights) = el.partition(_.isLeft)
         (lefts.map(_.left.get), rights.map(_.right.get))
       }
splitEitherList: [A, B](el: List[Either[A,B]])(List[A], List[B])

scala> val el : List[Either[Int, String]] = List(Left(1), Right("Success"), Left(42))
el: List[Either[Int,String]] = List(Left(1), Right(Success), Left(42))

scala> val (leftValues, rightValues) = splitEitherList(el)
leftValues: List[Int] = List(1, 42)
rightValues: List[String] = List("Success")

How to split a List[Either[A, B]] - scala - html, I want to split a List[Either[A, B]] in two lists. Is there a better way ? def lefts[A, B](​eithers : List[Either[A, B]]) : List[A] = eithers.collect { case Left(l) => l} def rights[A,  The split () method splits a string into a list. You can specify the separator, default separator is any whitespace. Note: When maxsplit is specified, the list will contain the specified number of elements plus one. string .split ( separator, maxsplit ) Parameter Values. Optional. Specifies the separator to use when splitting the string. By

If scalaz is one of your dependencies I would simply use separate:

import scalaz.std.list._
import scalaz.std.either._
import scalaz.syntax.monadPlus._

val el : List[Either[Int, String]] = List(Left(1), Right("Success"), Left(42))

scala> val (lefts, rights) = el.separate
lefts: List[Int] = List(1, 42)
rights: List[String] = List(Success)

Logic And Declarative Language, This split procedure clearly goes some way towards sorting a list of elements and element was either the largest or smallest element in the list, then the result of part divide( [a,b,c,d,e] ,X,Y) - X : [a,C,el Y : [b,Cl] and the fact that the resulting  The split () method in Python returns a list of the words in the string/line , separated by the delimiter string. This method will return one or more new strings. All substrings are returned in the list datatype. string.split (separator, max) separator : The is a delimiter. The string splits at this specified separator. If is not provided then

Starting Scala 2.13, most collections are now provided with a partitionMap method which partitions elements based on a function which returns either Right or Left.

In our case, we don't even need a function that transforms our input into Right or Left to define the partitioning as we already have Rights and Lefts. Thus a simple use of identity:

val (lefts, rights) = List(Right(2), Left("a"), Left("b")).partitionMap(identity)
// lefts: List[String] = List(a, b)
// rights: List[Int] = List(2)

EitherSplit.scala · GitHub, Mine, fix return type. def split1fix(data: List[Either[String, Int]]): Either[List[String], List[Int]] = {. val either = data.partition(_.isLeft) match {. case (Nil, ints) => Right(for​  I want to split a List[Either[A, B]] in two lists. Is there a better way ? def lefts[A, B](eithers : List[Either[A, B]]) : List[A] = eithers.collect { case Left(l

You can do it with:

val (lefts, rights) = eithers.foldRight((List[Int](), List[String]()))((e, p) => e.fold(l => (l :: p._1, p._2), r => (p._1, r :: p._2)))

Partition with Either on Traversable, * returned in the second list. Any element that conforms to both B and C will be returned in the first list. */. def split[A <: AnyRef,  split () method returns a list of strings after breaking the given string by the specified separator. separator : The is a delimiter. The string splits at this specified separator. If is not provided then any white space is a separator. maxsplit : It is a number, which tells us to split the string into maximum of provided number of times.

A compact, but not CPU-effictive solution:

val lefts = list.flatMap(_.left.toOption)
val rights = list.flatMap(_.right.toOption)

Cats: EitherT, 0, a / b, "Cannot divide by zero") // divide: (a: Double, b: Double)Either[String List[Either[String, Int]] = List(Right(250)) val numberET: EitherT[List, String, Int]  A/B split testing, which pits two page variations with a single differentiating element against each other, can be a better choice for beginning webmasters than the more complex multivariate

Encyclopedia of Cryptography and Security, TR EV TE Final performance measure Full dataset Split Biometric Systems Flowchart oftypical evaluation procedure B Biometric Systems Evaluation. If the classifier returns a ranked list, either the average error is computed over the entire  I am trying to split my list into a dictionary and I wrote a function for it. It takes in a list and gets the list length. If the length of the list is 253 , it creates a dictionary with 26 keys - this is calculated by rounding up the number to a higher 10 (250 will create 25 keys, 251-259 will create 26 keys).

Cats: Either, Either. In day-to-day programming, it is fairly common to find ourselves writing val moreThrowing: String => List[Char] = ??? val magic = throwsSomeStuff. Monad implicit def eitherMonad[Err]: Monad[Either[Err, ?]] = new Monad[Either[​Err, ?]] tailRecM[A, B](a: A)(f: A => Either[Err, Either[A, B]]): Either[Err, B] = f(a) match  Case analysis for the Either type. If the value is Left a, apply the first function to a; if it is Right b, apply the second function to b.. Examples Expand. We create two values of type Either String Int, one using the Left constructor and another using the Right constructor.

Learn You Some Erlang for Great Good!: A Beginner's Guide, Moreover, if you want to add elements to a list—either in the middle or at the end​— you C l B H [c] = [a|[b]] ++ [c] [blLClll Do you see all that rewriting? in certain ways, and there is still a cost to modifying binaries, splitting them, and so on. A complete one liner: In Python, inputs are strings by default applying a split() function to a string splits it into a list of strings, then with the help of map() function we can convert all the strings into integers.

Comments
  • Edit : (lefts.map(.left.get), rights.map(.right.get)) becomes (lefts.flatMap(.left.toOption), rights.flatMap(.right.toOption))
  • Care to provide a more complete answer with all required imports? And the specific scalaz version?
  • libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.2.2", and import scalaz.Scalaz._. more info: stackoverflow.com/questions/36878459/…
  • And in case you use cats, you have separate too! typelevel.org/cats/api/cats/syntax/…