Questions And Answers

More Tutorials

Scala For Expressions


Basic For Loop

for (x <- 1 to 10)
 println("Iteration number " + x)

This demonstrates iterating a variable, x, from 1 to 10 and doing something with that value. The return type of this for comprehension is Unit.

Basic For Comprehension

This demonstrates a filter on a for-loop, and the use of yield to create a 'sequence comprehension':

for ( x <- 1 to 10 if x % 2 == 0)
 yield x

The output for this is:

scala.collection.immutable.IndexedSeq[Int] = Vector(2, 4, 6, 8, 10)

A for comprehension is useful when you need to create a new collection based on the iteration and it's filters.

Nested For Loop

This shows how you can iterate over multiple variables:

for {
 x <- 1 to 2
 y <- 'a' to 'd'
} println("(" + x + "," + y + ")")

(Note that to here is an infix operator method that returns an inclusive range. See the definition here.)

This creates the output:


Note that this is an equivalent expression, using parentheses instead of brackets:

for (
 x <- 1 to 2
 y <- 'a' to 'd'
) println("(" + x + "," + y + ")")

In order to get all of the combinations into a single vector, we can yield the result and set it to a val:

val a = for {
 x <- 1 to 2
 y <- 'a' to 'd'
} yield "(%s,%s)".format(x, y)
// a: scala.collection.immutable.IndexedSeq[String] = Vector((1,a), (1,b), (1,c), (1,d),
(2,a), (2,b), (2,c), (2,d))


In this page (written and validated by ) you learned about Scala For Expressions . What's Next? If you are interested in completing Scala tutorial, your next topic will be learning about: Scala Functions.

Incorrect info or code snippet? We take very seriously the accuracy of the information provided on our website. We also make sure to test all snippets and examples provided for each section. If you find any incorrect information, please send us an email about the issue:

Share On:

Mockstacks was launched to help beginners learn programming languages; the site is optimized with no Ads as, Ads might slow down the performance. We also don't track any personal information; we also don't collect any kind of data unless the user provided us a corrected information. Almost all examples have been tested. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. By using, you agree to have read and accepted our terms of use, cookies and privacy policy.