Steps

1. How to create a Stream with 3 numbers using #::

The code below shows how to create a Stream with 3 numbers using #::.

println("Step 1: How to create a Stream with 3 numbers using #::")
val stream1: Stream[Int] = 1 #:: 2 #:: 3 #:: Stream.empty
println(s"Elements of stream1 = $stream1")

You should see the following output when you run your Scala application in IntelliJ:

Step 1: How to create a Stream with 3 numbers using #::
Elements of stream1 = Stream(1, ?)

NOTE:

• When we tried to print the elements of the Stream, only the first element of the Stream was printed!
• As mentioned earlier, the elements of Streams are lazily computed.

2. How to create a Stream with 3 numbers using Stream.cons

The code below shows how to create a Stream with 3 numbers using Stream.cons.

import scala.collection.immutable.Stream.cons
println("\nStep 2: How to create a Stream with 3 numbers using Stream.cons")
val stream2: Stream[Int] = cons(1, cons(2, cons(3, Stream.empty) ) )
println(s"Elements of stream2 = ${stream2}")

You should see the following output when you run your Scala application in IntelliJ:

Step 2: How to create a Stream with 3 numbers using Stream.cons
Elements of stream2 = Stream(1, ?)

NOTE:

• Similar to Step 1 above, only the first element of the Stream was printed.
• Stream.cons is commonly known and referred to as the cons operator.

3. How to print all 3 numbers from stream2 using the take function

The code below shows how to print all 3 numbers from stream2 using the take function.

println("\nStep 3: How to print all 3 numbers from stream2 using the take function")
print("Take first 3 numbers from stream2 = ")
stream2.take(3).print

print("\nTake first 10 numbers from stream2 = ")
stream2.take(10).print

You should see the following output when you run your Scala application in IntelliJ:

Step 3: How to print all 3 numbers from stream2 using the take function
Take first 3 numbers from stream2 = 1, 2, 3, empty
Take first 10 numbers from stream2 = 1, 2, 3, empty

NOTE:

• When we tried to take 10 numbers from the Stream, although it only contained 3 elements, it did not throw any IndexOutOfBoundsException.

4. How to define an infinite Stream of numbers using Stream.cons

The code below shows how to define an infinite Stream of numbers using Stream.cons.

println("\n\nStep 4: How to define an infinite Stream of numbers using Stream.cons")
def inifiniteNumberStream(number: Int): Stream[Int] = Stream.cons(number, inifiniteNumberStream(number + 1))
print("Take only the first 20 numbers from the infinite number stream = ")
inifiniteNumberStream(1).take(20).print

You should see the following output when you run your Scala application in IntelliJ:

Step 4: How to define an infinite Stream of numbers using Stream.cons
Take only the first 20 numbers from the infinite number stream = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, empty

5. How to define an infinite stream of numbers using Stream.from

The code below shows how to define an infinite stream of numbers using Stream.from.

println("\n\nStep 5: How to define an infinite stream of numbers using Stream.from")
val stream3: Stream[Int] = Stream.from(1)
print("Take only the first 20 numbers from the infinite number stream = ")
stream3.take(20).print

You should see the following output when you run your Scala application in IntelliJ:

Step 5: How to define an infinite stream of numbers using Stream.from
Take only the first 20 numbers from the infinite number stream = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, empty

6. How to initialize an empty Stream

The code below shows how to initialize an empty Stream.

println("\n\nStep 6: How to initialize an empty Stream")
val emptyStream: Stream[Int] = Stream.empty[Int]
println(s"Empty Stream = $emptyStream")

You should see the following output when you run your Scala application in IntelliJ:

Step 6: How to initialize an empty Stream
Empty Stream = Stream()