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scalafunctional-programmingyield

What is Scala's yield?

I understand Ruby and Python's yield. What does Scala's yield do?

Solution

  • It is used in sequence comprehensions (like Python's list-comprehensions and generators, where you may use yield too).

    It is applied in combination with for and writes a new element into the resulting sequence.

    Simple example (from scala-lang)

    /** Turn command line arguments to uppercase */
object Main {
  def main(args: Array[String]) {
    val res = for (a <- args) yield a.toUpperCase
    println("Arguments: " + res.toString)
  }
}

    The corresponding expression in F# would be

    [ for a in args -> a.toUpperCase ]

    or

    from a in args select a.toUpperCase

    in Linq.

    Ruby's yield has a different effect.