Foreach loop over a list Scala?

Question

I have a list in scala that looks like the following:

val totalQuote: List[List[String]] = List(List("a","b","c"),List("1","2","3"),List("d","e","f"),List("4","5","6"))

I want to print out every element in the list using a foreach loop. However when I run this:

totalQuote.foreach{ e =>
      val(a,b) = e
      println(a)
    }

I get the following error:

Error:(17, 10) constructor cannot be instantiated to expected type;
 found   : (T1, T2)
 required: List[String]
      val(a,b) = e

Not sure how to resolve this!

Andrey Tyukin · Accepted Answer · 2018-05-11 21:53:11Z

3

You could use nested for-loops:

for {
  list <- totalQuote
  character <- list
} println(character)

Without for, this could also be written as:

totalQuote.foreach { list =>
  list foreach println
}

or even

totalQuote foreach (_ foreach println)

If you want to take only the first two elements out of every list, you could combine for with pattern-matching as follows:

for (a :: b :: _ <- totalQuote) { 
  println(a)
  println(b) 
}

or

for (a :: b :: _ <- totalQuote; x <- List(a, b)) println(x)

answered May 11, 2018 at 21:53

Andrey Tyukin

45.1k4 gold badges65 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Tim · Accepted Answer · 2018-05-11 17:59:24Z

1

The type of e is List[String] but

val (a,b) = e

only works if e is a tuple. Try this

val a::b::_ = e

answered May 11, 2018 at 17:59

Tim

27.6k2 gold badges18 silver badges32 bronze badges

Chaitanya · Accepted Answer · 2018-05-11 17:58:19Z

0

You can simply use the following to print each element of the list

  totalQuote.flatten.foreach{x => println(x)}

answered May 11, 2018 at 17:58

Chaitanya

3,65417 silver badges41 bronze badges