Replace elements in one array from elements in other array in Scala

Question

I am having two arrays. Size of first array is larger than second one.

 var first  = (1 to 20).toArray
 var second = (1 to 5).toArray

I want to Replace first n elements of first array with the elements of second array. Where n is length of second array. Using For loop I can easily do this in following way

 var n = second.length
 for(i <- 0 until n)
 {
  first(i) = second(i)
 }

I want to ask is there any other way to perform same operation in Scala in more functional way?

What do you mean by "more functional way"? Are you looking for a solution without mutating the first array? — k0pernikus
– k0pernikus, Commented Aug 14, 2019 at 10:22
You could use copyToArray like, second.copyToArray(first). Also, for what you need you could replace var with val. — Leo C
– Leo C, Commented Aug 14, 2019 at 10:37
In the end, even a functional approach will loop the data. Furthermore, a functional approach will create another array consisting of the result and therefore have a larger memory consumption. — k0pernikus
– k0pernikus, Commented Aug 14, 2019 at 10:39
If you want to write in a functional way, you should begin by avoiding ever using Array in the first place, just sayin'... — Seth Tisue
– Seth Tisue, Commented Aug 14, 2019 at 14:44

Pedro Correia Luis · Accepted Answer · 2019-08-14 10:40:15Z

5

You can do this:

var first  = (1 to 20).toArray
var second = (1 to 5).toArray

val third = second ++ first.drop(second.length)

result:

third: Array[Int] = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)

edited Aug 14, 2019 at 10:40

answered Aug 14, 2019 at 10:37

Pedro Correia Luis

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3 Comments

k0pernikus Over a year ago

This IIRC either returns a vector or IndexedSeq[Int], so toArray may be necessary.

yari Over a year ago

first = second ++ first.drop(second.length) This will return first array with updated elements

Pedro Correia Luis Over a year ago

@yari yes, but since you asked a more functional way, it is better to use val´s instead of vars, if you really want to replace and keep vars, then it is exactly how you wrote.

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