CODEWITHSUNDEEP
scala
I82Much
I82Much

Reputation: 27326

Scala - printing arrays

It seems like the support for printing arrays is somewhat lacking in Scala. If you print one, you get the default garbage you'd get in Java:

scala> val array = Array.fill(2,2)(0)             
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))

scala> println(array)
[[I@d2f01d

Furthermore, you cannot use the Java toString/deepToString methods from the java.util.Arrays class: (or at least I cannot figure it out)

scala> println(java.util.Arrays.deepToString(array))
<console>:7: error: type mismatch;
 found   : Array[Array[Int]]
 required: Array[java.lang.Object]
       println(java.util.Arrays.deepToString(array))

The best solution I could find for printing a 2D array is to do the following:

scala> println(array.map(_.mkString(" ")).mkString("\n"))
0 0
0 0

Is there a more idiomatic way of doing this?

Upvotes: 74

Views: 82599

Answers (8)

BSP
BSP

Reputation: 775

Array(1, 7, 2, 9) foreach println

Minor modification of rupert160's answer. No need for dots or parenthesis.

Upvotes: 0

rupert160
rupert160

Reputation: 1531

I rather like this one:

Array(1, 7, 2, 9).foreach(println)

Upvotes: 3

Noha Elprince
Noha Elprince

Reputation: 1934

Try simply this:

  // create an array
  val array1 = Array(1,2,3)
  // print an array elements seperated by comma
  println(array1.mkString(","))
  // print an array elements seperated by a line
  println(array1.mkString("\n"))

  // create a function
  def printArray[k](a:Array[k])= println(a.mkString(","))
  printArray(array1)

Upvotes: 6

akuriako
akuriako

Reputation: 447

Adding little more to Arjan's answer - you can use the mkString method to print and even specify the separator between elements. For instance :

val a = Array(1, 7, 2, 9)
a.mkString(" and ")
// "1 and 7 and 2 and 9"
a.mkString("<", ",", ">") //mkString(start: String, sep: String, end: String)
// "<1,7,2,9>"

Upvotes: 17

David Weber
David Weber

Reputation: 1995

You can get neat formatting of Array[Array[Somethings]] with custom separators for the inner as well as the outer array follows:

    def arrayToString(a: Array[Array[Int]]) : String = {
       val str = for (l <- a) yield l.mkString("{", ",", "}")
       str.mkString("{",",\n","}")
    }

    val foo = Array.fill(2,2)(0)
    println(arrayToString(foo))

This results in:

    {{0,0},
    {0,0}}

Upvotes: 2

Enrico Susatyo
Enrico Susatyo

Reputation: 19790

The "functional programming" way to do this (as far as I concern) is:

scala> array foreach{case a => a foreach {b => print(b.toString + " ")}; print('\n')}
0 0 
0 0

Or if you don't really care about the spacing:

scala> array foreach{a => a foreach println}
0
0
0
0

IMHO, functional programming can get a little messy, if it takes too long to make this, I'd say just go with the imperative way.

Upvotes: 1

Eastsun
Eastsun

Reputation: 18859

How about this:

scala> val array = Array.fill(2,2)(0)
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))

scala> import scala.runtime.ScalaRunTime._
import scala.runtime.ScalaRunTime._

scala> val str = stringOf(array)
str: String =
Array(Array(0, 0), Array(0, 0))

Upvotes: 39

Arjan Blokzijl
Arjan Blokzijl

Reputation: 6888

In Scala 2.8, you can use the deep method defined on Array, that returns an IndexedSeq cointaining all of the (possibly nested) elements of this array, and call mkString on that:


scala> val array = Array.fill(2,2)(0)
array: Array[Array[Int]] = Array(Array(0, 0), Array(0, 0))

scala> println(array.deep.mkString("\n"))
Array(0, 0)
Array(0, 0)

The IndexedSeq returned does have a stringprefix 'Array' by default, so I'm not sure whether this gives precisely what you wanted.

Upvotes: 114

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