Cross product in Scala

by

You can do this pretty straightforwardly with an implicit class and a for-comprehension in Scala 2.10:

implicit class Crossable[X](xs: Traversable[X]) {
  def cross[Y](ys: Traversable[Y]) = for { x <- xs; y <- ys } yield (x, y)
}

val xs = Seq(1, 2)
val ys = List("hello", "world", "bye")

And now:

scala> xs cross ys
res0: Traversable[(Int, String)] = List((1,hello), (1,world), ...

This is possible before 2.10—just not quite as concise, since you’d need to define both the class and an implicit conversion method.

You can also write this:

scala> xs cross ys cross List('a, 'b)
res2: Traversable[((Int, String), Symbol)] = List(((1,hello),'a), ...

If you want xs cross ys cross zs to return a Tuple3, however, you’ll need either a lot of boilerplate or a library like Shapeless.

More Related Contents:

  1. What is Scala’s yield?
  2. What is the difference between Scala’s case class and class?
  3. What is the motivation for Scala assignment evaluating to Unit rather than the value assigned?
  4. Difference between reduce and foldLeft/fold in functional programming (particularly Scala and Scala APIs)?
  5. Abort early in a fold
  6. What is the difference between def foo = {} and def foo() = {} in Scala?
  7. Scala currying vs partially applied functions
  8. val-mutable versus var-immutable in Scala
  9. Using Either to process failures in Scala code
  10. When to use parenthesis in Scala infix notation
  11. When and why should one use Applicative Functors in Scala
  12. Function returns an empty List in Spark
  13. Functional programming, Scala map and fold left [closed]
  14. What is a function literal in Scala?
  15. How to sort a list in Scala by two fields?
  16. Can I zip more than two lists together in Scala?
  17. Functional Reactive Programming in Scala [closed]
  18. Using partial functions in Scala – how does it work?
  19. What’s the difference between => , ()=>, and Unit=>
  20. What is the advantage of using abstract classes instead of traits?
  21. Split 1 column into 3 columns in spark scala
  22. How to read files from resources folder in Scala?
  23. Scala return statements in anonymous functions
  24. What is the difference between `##` and `hashCode`?
  25. How to add “provided” dependencies back to run/test tasks’ classpath?
  26. Spark-Monotonically increasing id not working as expected in dataframe?
  27. What does a single apostrophe mean in Scala? [duplicate]
  28. Queries with streaming sources must be executed with writeStream.start();
  29. Singletons as Synthetic classes in Scala?
  30. Understanding the Aux pattern in Scala Type System

Leave a Comment