Scala Trait Traversable | Set-1
Last Updated :
12 Apr, 2019
Introduction:
A root trait of the entire class of the Scala collections is Trait Traversable. It is available at the uppermost position of the collection hierarchy. It has uniquely one abstract operation, which is foreach. Here each of the operations are assured to be executed in a single-threaded approach.
Syntax:
def foreach[U](f: Elem => U)
Here, the operation f is concerned with all the elements of the collection and Elem => U is the type of operation, where “Elem” is the type of elements in the Scala’s collection and “U” is an inconsistent result type.
Some Important points:
- Traversable is accomplished by the Scala’s Collection classes.
- It is obligatory for Traversable to define foreach method only, as Traversable can inherit all the other methods.
- The foreach method could traverse all the elements of the Scala’s collection class.
- There are numerous concrete methods which are defined by Traversables.
- List, Array, Map, Set, and many more are the subclass of Traversables.
Operations performed by the Class Traversable are as follows:
- Abstract Method:
The only abstract method here is foreach, which can traverse over all the elements of the Collection.
Example :
object CS
{
def main(args : Array[String])
{
val x = Array( "GEEKS" , "FOR" , "GEEKS" )
x.foreach { E =>
val y = E.toLowerCase
println(y)
}
}
}
|
Here, all the elements of the Array stated above are traversed by foreach method and then they are converted from uppercase to lowercase.
Example:
object GFG
{
def main(args : Array[String])
{
val l = List( 2 , 6 , 8 , 7 , 10 , 11 , 13 )
l.foreach(n => println(n * 6 ))
}
}
|
Output:
12
36
48
42
60
66
78
Here, foreach method traverses all the numbers of the list and multiplies each of them.
- Addition operation:
Here, Addition operation i.e, ++ adds two Traversables together or adds each of the elements of an iterator to a Traversable.
Example:
object GFG
{
def main(args : Array[String])
{
val x = Set( 7 , 8 , 9 , 10 )
val y = List( 1 , 5 , 8 , 18 )
val s 1 = x ++ y
val s 2 = y ++ x
println(s 1 )
println(s 2 )
}
}
|
Output:
Set(5, 10, 1, 9, 7, 18, 8)
List(1, 5, 8, 18, 7, 8, 9, 10)
Here, when a Set is added to a List then a Set is generated and when a List is added to a Set then a List is generated.
- Map operations:
The three Map operations are map, flatMap, and collect.
These Map operations create a new collection by assigning a few function to the elements of Scala collection.
Example :
object GFG
{
def main(args : Array[String])
{
val x = Set( 8 , 9 , 5 , 10 )
val y = x.map( _ * 9 )
println(y)
}
}
|
Output:
Set(72, 81, 45, 90)
Here, the Map operation (i.e, map) will assign the stated function on each elements of a Traversable and will return a new collection as output.
Example :
object GFG
{
def main(args : Array[String])
{
val q = List(List( 7 ), List( 8 , 9 , 10 ), List( 11 , 12 , 13 ))
val r = q.flatMap( _ .map( _ + 3 ))
println(r)
}
}
|
Output:
List(10, 11, 12, 13, 14, 15, 16)
Here, the flatMap will assign the stated function on each elements within the elements and then will Concatenate the output.
Example :
object GFG
{
def main(args : Array[String])
{
val x = List( 9 , 3 , 5 , 11 , 15 , 4 )
val y = x.collect
{
case z : Int if (z % 3 == 0 ) => z + 2
}
println(y)
}
}
|
Here, collect will assign a partial function to each elements of Traversable and will give a non-identical collection as output.
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