How to create an immutable array within a mutable array in scala?

Question

So I am trying to create an immutable array of size 10 within a mutable array in scala. In this immutable array I want to store key, value pairs. so far I have this mutable array:

val array1 = mutable.ArrayBuffer[Option[IndexedSeq[(A,B)]]]()

Now to create an immutable buffer in array1 would I just do:

array1(0) = immutable.ArrayBuffer[](10)

I am confused on what would go within the brackets of the immutable buffer for the type.

I don't understand what exactly do you want to do? You are trying to assign a immutable.ArrayBuffer to the first position of array1, is what what you want to do? — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Nov 10, 2021 at 14:29
Well array1 is an mutable.ArrayBuffer[Option[IndexedSeq[(A,B)]]] thus the elements must be Option[IndexedSeq[(A,B)]] not an immutable.ArrayBuffer so what you want to do doesn't make sense. — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Nov 10, 2021 at 14:37

Aivean · Accepted Answer · 2021-11-10 22:18:26Z

1

There is no immutable.ArrayBuffer. ArrayBuffer is mutable.

Trait IndexedSeq can correspond to both immutable and mutable collections, so you have options what to use as your inner elements:

type A = Int
type B = Int

val array1 = mutable.ArrayBuffer[Option[IndexedSeq[(A,B)]]]()

// Adds immutable Vector
array1 += Some(IndexedSeq[(A, B)]( (1,2), (3,4) ))

// Adds mutable ArrayBuffer
array1 += Some(ArrayBuffer[(A, B)]( (1,2), (3,4) ))

Note, since your inner element is Option[IndexedSeq[...]], you need to wrap the elements you are adding in Some.

answered Nov 10, 2021 at 22:18

Aivean

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