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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)
        }
    }
    Output:
    4
    

    Here, count will display the number of elements of the collection which satisfies the given condition.

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