Scala Trait Traversable | Set-3

Last Updated : 15 Apr, 2019

Prerequisite :
Scala Trait Traversable | Set-1
Scala Trait Traversable | Set-2
It is recommended to see (Set-1, Set-2) before this Set.
The operations are as follows:

Sub-Collection retrieval operations:
The operations here are slice, drop, dropWhile, filter, filterNot, tail, take, takeWhile, and init. These operations are utilized to return some sub collection.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(17, 19, 21, 29, 31) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.init  
  
        // Displays all the elements of  
        // the List except the last one 
        println(y) 
    } 
} 

Output:

List(17, 19, 21, 29)

Here, init retrieves all the elements of the Traversable collection except the last element.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(17, 19, 21, 29, 31) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.tail 
  
        // Displays all the elements of  
        // the List except the first one 
        println(y) 
    } 
} 

Output:

List(19, 21, 29, 31)

Here, tail retrieves all the elements of the Traversable collection except the first element.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(27, 29, 31, 49, 51, 56) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.slice(2, 5) 
  
        // Displays the elements  
        // from index 2 to 4  
        println(y) 
    } 
} 

Output:

List(31, 49, 51)

Here, slice will return the elements from the given range of index excluding last index.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(37, 49, 51, 69, 71, 86) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.take(2) 
  
        // Displays the first two  
        // elements of the list 
        println(y) 
    } 
} 

Output:

List(37, 49)

Here, this operation will return numbers of elements given in the argument of the take operation.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(33, 34, 36, 37, 39, 40, 44) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.drop(4) 
  
        // Displays all the elements of  
        // the list except the first  
        // four elements 
        println(y) 
    } 
} 

Output:

List(39, 40, 44)

Here, this operation will return all the elements of the collection except the first number of elements given in the argument of drop operation.
Example:

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(2, 5, 9, 13, 17, 20) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.dropWhile(_ < 10) 
  
        // Displays all the elements of  
        // the list which are greater  
        // than or equal to 10 
        println(y) 
    } 
} 

Output:

List(13, 17, 20)

Here, dropWhile will drop the elements until the given condition is satisfied and returns rest of the left elements.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(2, 5, 9, 10, 13, 17, 20) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.takeWhile(_ < 13) 
          
        // Displays all the elements of  
        // the list which are less  
        // than 13 
        println(y) 
    } 
} 

Output:

List(2, 5, 9, 10)

Here, takeWhile will take the elements until the given condition is satisfied and returns these elements.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(9, 65, 99, 10, 23, 17, 12) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.filter(_ < 23) 
  
        // Displays all the elements of  
        // the list which are less  
        // than 23 
        println(y) 
    } 
} 

Output:

List(9, 10, 17, 12)

Here, filter will return all the elements until the given condition is satisfied and drops the rest.
Example :

// Scala program of Sub-Collection 
// retrieval operation 
  
// Creating object  
object SubCollection 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(9, 65, 99, 10, 23, 17, 12) 
  
        // Applying Sub-Collection  
        // retrieval operation 
        val y = x.filterNot(_ < 23) 
  
        // Displays all the elements of  
        // the list which are greater  
        // than or equal to 23 
        println(y) 
    } 
} 

Output:

List(65, 99, 23)

Here, filterNot will return all the elements which does not satisfies the given condition and drops the rest.

Subdivision operations:
These operations include span, partition, splitAt, groupBy. These operations are utilized to break the elements of the collection and return some sub-collections.
Example :

// Scala program of Subdivision  
// operations 
  
// Creating object  
object Subdivision 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val q = List(7, 9, 11, 15, 17, 19, 22) 
  
        // Applying Subdivision  
        // operations 
        val r = q.span(_ < 15) 
  
        // Displays all the elements in  
        // two parts 
        println(r) 
    } 
} 

Output:

(List(7, 9, 11), List(15, 17, 19, 22))

Here, span will split the given Traversable collection of element into two parts where, first part is obtained by performing takeWhile operation and second part is obtained by performing dropWhile operation.
Example :

// Scala program of Subdivision  
// operations 
  
// Creating object  
object Subdivision 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val q = List(17, 29, 31, 36, 37, 39, 42) 
  
        // Applying Subdivision  
        // operations 
        val r = q.partition(_ < 35) 
  
        // Displays all the elements in  
        // two parts 
        println(r) 
    } 
} 

Output:

(List(17, 29, 31), List(36, 37, 39, 42))

Here, partition will divide the collection into two parts where, first part will return the elements till the given condition is satisfied and second part will return rest of the elements.
Example :

// Scala program of Subdivision  
// operations 
  
// Creating object  
object Subdivision 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val q = List(17, 29, 31, 36, 37, 39, 42) 
  
        // Applying Subdivision  
        // operations 
        val r = q.splitAt(4) 
  
        // Displays all the elements in  
        // two parts 
        println(r) 
    } 
} 

Output:

(List(17, 29, 31, 36), List(37, 39, 42))

Here, splitAt will divide the elements of the collection into two parts in the given position where, first part will be obtained by performing take operation and second part will be obtained by performing drop operation.
Example :

// Scala program of Subdivision  
// operations 
  
// Creating object  
object Subdivision 
{ 
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(21, 20, 33, 40, 27, 62) 
  
        // Applying Subdivision  
        // operation  
        val y = x.groupBy  
        { 
  
            // Partial function 
            case z : Int if (z % 3 == 0) => z + 3
            case z : Int if (z % 2 == 0) => z + 2
        } 
      
        // Displaying Map of lists 
        println(y) 
    } 
} 

Output:

Map(42 -> List(40), 24 -> List(21), 64 -> List(62), 22 -> List(20), 36 -> List(33), 30 -> List(27))

Here, groupBy will divide the Traversable collection on the basis of the partial function given and will return a Map.

Element test methods:
These methods include forall, exists, and count. These methods are utilized to test the given collection of Traversable on the basis of stated conditions.
Example :

// Scala program of Element  
// test 
  
// Creating object  
object Elementtest 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(21, 20, 33, 40, 27, 62) 
  
        // Applying Element test  
        // method 
        val y = x forall (_ < 63)  
  
        // Displays true if all the  
        // elements are lesser  
        // than 63 
        println(y) 
    } 
} 

Output:

true

Here, forall will return true if all the elements of the collection satisfies the given condition else returns false.
Example :

// Scala program of Element  
// test 
  
// Creating object  
object Elementtest 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(21, 20, 33, 40, 27, 62) 
  
        // Applying Element test  
        // method 
        val y = x exists (_ < 30)  
  
        // Displays true if some of  
        // the elements are lesser  
        // than 30 
        println(y) 
    } 
} 

Output:

true

Here, exists will return true if some of the elements of the collection satisfies the given condition else returns false.
Example :

// Scala program of Element  
// test 
  
// Creating object  
object Elementtest 
{ 
  
    // Main method 
    def main(args: Array[String])  
    { 
  
        // Creating List of numbers  
        val x = List(21, 20, 33, 40, 27, 62) 
  
        // Applying Element test  
        // method 
        val y = x count(_ < 40)  
  
        // Displays the number of  
        // elements satisfying the  
        // given condition 
        println(y) 
    } 
} 