We continue with more Scala on the topic of Vectors in this post. For
all the work in this post, we will use Read-Evaluate-Print-Loop
Scala interpreter. Some familiarity
with Java will be of great help in understanding Scala. In this post, we will
look at how Vectors are defined along with some features of Vectors in Scala.
After looking at Arrays in last post, we will see how Vector are useful in Scala programs. Vector is a immutable data structure that provides random access and updates in effectively constant time. It also facilitates very fast append and prepend.
Vectors can be defined as shown below:
i) An empty Vector:
val Vector0: Vector[Int] = Vector()
The results are shown below:
scala> val Vector0: Vector[Int] = Vector()
Vector0: Vector[Int] = Vector()
scala> Vector0
res7: Vector[Int] = Vector()
ii) A Vector initialized with values:
val Vector1 = Vector(1,1,2,3,4,5)
val Vector2 = Vector(5,6,7,8,9,10,10)
The results are shown below:
scala> val Vector1 = Vector(1,1,2,3,4,5)
Vector1: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5)
scala> val Vector2 = Vector(5,6,7,8,9,10,10)
Vector2: scala.collection.immutable.Vector[Int] = Vector(5,6, 7, 8, 9, 10, 10)
Most of the methods in Vector have the same behavior that we have seen in the case of Arrays here. We will see some of methods that can be applied on Vectors:
1) :+ : An element is appended to vector
scala> Vector1 :+ 100
res3: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5, 100)
2) +: : An element is prepended to array
scala> 100 +: Vector1
res4: scala.collection.immutable.Vector[Int] = Vector(100, 1, 1, 2, 3, 4, 5)
3) addString : Takes a StringBuilder and returns a StringBuilder with all elements appended with a start, end and a separator
scala> Vector1 addString (b=new StringBuilder("Hello"),start=" Start ",sep=":",end=" End ")
res9: StringBuilder = Hello Start 1:1:2:3:4:5 End
4) aggregate : Aggregates results after application of an operator to different elements
scala> Vector(1,1,2,3,4,5).aggregate(0)({ (sum, i) => sum + i }, { (p1, p2) => p1 + p2 })
res13: Int = 16
5) apply : Selects element by index
scala> Vector1 apply 1
res14: Int = 1
6) diff : Returns difference between operands
scala> Vector1 diff Vector2
res24: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4)
7) iterator : Returns a Vector Iterator. This iterator can then be used to iterate over the different elements of the Vector
scala> val Vector1_Iterator = Vector1.iterator
Vector1_Iterator: scala.collection.immutable.VectorIterator[Int] = non-empty iterator
scala> while (Vector1_Iterator.hasNext) {
| println(Vector1_Iterator.next())
| }
1
1
2
3
4
5
8) reverseIterator : Returns a Iterator with elements in reverse order
scala> while (Vector1_Reverse_Iterator.hasNext) {
| println(Vector1_Reverse_Iterator.next())
| }
5
4
3
2
1
1
9) union : Returns union of operands
scala> Vector1 union Vector2
res29: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10, 10)
10) zipWithIndex: Zips the vector with its indices
scala> Vector1.zipWithIndex
res30: scala.collection.immutable.Vector[(Int, Int)] = Vector((1,0), (1,1), (2,2), (3,3), (4,4), (5,5))
This concludes the discussion of Vectors in Scala.
After looking at Arrays in last post, we will see how Vector are useful in Scala programs. Vector is a immutable data structure that provides random access and updates in effectively constant time. It also facilitates very fast append and prepend.
Vectors can be defined as shown below:
i) An empty Vector:
val Vector0: Vector[Int] = Vector()
The results are shown below:
scala> val Vector0: Vector[Int] = Vector()
Vector0: Vector[Int] = Vector()
scala> Vector0
res7: Vector[Int] = Vector()
ii) A Vector initialized with values:
val Vector1 = Vector(1,1,2,3,4,5)
val Vector2 = Vector(5,6,7,8,9,10,10)
The results are shown below:
scala> val Vector1 = Vector(1,1,2,3,4,5)
Vector1: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5)
scala> val Vector2 = Vector(5,6,7,8,9,10,10)
Vector2: scala.collection.immutable.Vector[Int] = Vector(5,6, 7, 8, 9, 10, 10)
Most of the methods in Vector have the same behavior that we have seen in the case of Arrays here. We will see some of methods that can be applied on Vectors:
1) :+ : An element is appended to vector
scala> Vector1 :+ 100
res3: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5, 100)
2) +: : An element is prepended to array
scala> 100 +: Vector1
res4: scala.collection.immutable.Vector[Int] = Vector(100, 1, 1, 2, 3, 4, 5)
3) addString : Takes a StringBuilder and returns a StringBuilder with all elements appended with a start, end and a separator
scala> Vector1 addString (b=new StringBuilder("Hello"),start=" Start ",sep=":",end=" End ")
res9: StringBuilder = Hello Start 1:1:2:3:4:5 End
4) aggregate : Aggregates results after application of an operator to different elements
scala> Vector(1,1,2,3,4,5).aggregate(0)({ (sum, i) => sum + i }, { (p1, p2) => p1 + p2 })
res13: Int = 16
5) apply : Selects element by index
scala> Vector1 apply 1
res14: Int = 1
6) diff : Returns difference between operands
scala> Vector1 diff Vector2
res24: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4)
7) iterator : Returns a Vector Iterator. This iterator can then be used to iterate over the different elements of the Vector
scala> val Vector1_Iterator = Vector1.iterator
Vector1_Iterator: scala.collection.immutable.VectorIterator[Int] = non-empty iterator
scala> while (Vector1_Iterator.hasNext) {
| println(Vector1_Iterator.next())
| }
1
1
2
3
4
5
8) reverseIterator : Returns a Iterator with elements in reverse order
scala> while (Vector1_Reverse_Iterator.hasNext) {
| println(Vector1_Reverse_Iterator.next())
| }
5
4
3
2
1
1
9) union : Returns union of operands
scala> Vector1 union Vector2
res29: scala.collection.immutable.Vector[Int] = Vector(1, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10, 10)
10) zipWithIndex: Zips the vector with its indices
scala> Vector1.zipWithIndex
res30: scala.collection.immutable.Vector[(Int, Int)] = Vector((1,0), (1,1), (2,2), (3,3), (4,4), (5,5))
This concludes the discussion of Vectors in Scala.
