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What specific data type is created when I use the Seq [T] constructor?

Scala allows me to instantiate an object that implements a property Seq

directly using this syntax:

val numbers: Seq[Int] = Seq(1, 2, 3)
val names: Seq[String] = Seq("Alice", "Bob", "Charles")
  • Since it Seq

    is a trait and not a specific implementation, what datatype is underlying numbers

    and names

    ?
  • What's the best way I could figure this out for myself?
  • Is it idiomatic to create an object object directly?

Thank!

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2 answers


List

is the default implementation. You can check this easily in the Scala REPL:

scala> val numbers: Seq[Int] = Seq(1, 2, 3)
numbers: Seq[Int] = List(1, 2, 3)

scala> val names: Seq[String] = Seq("Alice", "Bob", "Charles")
names: Seq[String] = List(Alice, Bob, Charles)


How much better (creation List

or Seq

) I think about preference. Both options are available and as far as I know the compiler doesn't complain when choosing one of them. I personally always use Seq

.

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For completeness, the answer can also be found in the Seq

(object, not trait) Scaladocs :



This object provides a set of operations for creating Seq values. The current default implementation of Seq is List.

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