Writing generic function to take in both Array and ArrayBuffer

Question

def foo[T <% Ordered[T]](array: Array[T], x: T) = {
      ........
}

So with foo I would like it to take in both Array and ArrayBuffer. However when I try and pass an ArrayBuffer, I get a type mistmatch

main.scala:67: error: type mismatch;
 found   : scala.collection.mutable.ArrayBuffer[Int]

I could simply solve this by making the array parameter an ArrayBuffer instead of an Array but that makes my method less flexible.

Martin · Accepted Answer · 2017-03-26 09:25:11Z

2

scala.collection.mutable.Seq will allow you to access and modify both Array and ArrayBuffer by index.

Note: view bound syntax is now deprecated, you can achieve the same thing with an implicit parameter:

def foo[T](array: scala.collection.mutable.Seq[T], x: T)(implicit ordering: Ordering[T]) = {
if (ordering.gt(array(0), x)) {
  array.update(0, x)
}

}

You can find more info about that in SI-7629 (https://issues.scala-lang.org/browse/SI-7629)

Hope that helps,

Thanks

answered Mar 26, 2017 at 9:25

Martin

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1 Comment

The implicit parameter you used is not equivalent to the view bound.

Cyrille Corpet · Accepted Answer · 2017-03-26 08:58:56Z

1

You can write

def foo[T <% Ordered[T]](seq: Seq[T], x: T) = ???

ArrayBuffer is indeed an implementation of Seq, and Array has an implicit conversion to it, so it will work just fine.

answered Mar 26, 2017 at 8:58

Cyrille Corpet

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