Steps

1. How to initialize a sequence of donut prices

The code below shows how to initialize a sequence of donut prices where each element in the sequence is of type Double.

println("Step 1: How to initialize a sequence of donut prices")
val prices: Seq[Double] = Seq(1.5, 2.0, 2.5)
println(s"Donut prices = $prices")

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

Step 1: How to initialize a sequence of donut prices
Donut prices = List(1.5, 2.0, 2.5)

2. How to sum all the donut prices using foldLeft function

The code below shows how to sum all the donut prices from the sequence by using the foldLeft method.

println("\nStep 2: How to sum all the donut prices using foldLeft function")
val sum = prices.foldLeft(0.0)(_ + _)
println(s"Sum = $sum")

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

Step 2: How to sum all the donut prices using foldLeft function
Sum = 6.0

NOTE:

• Note that we passed in a default or initial value of 0.0 to the foldLeft method because the sequence of Donuts was of type Double.

3. How to initialize a Sequence of donuts

The code below shows how to initialize a Sequence of donuts where each element is of type String.

println("\nStep 3: How to initialize a Sequence of donuts")
val donuts: Seq[String] = Seq("Plain", "Strawberry", "Glazed")
println(s"Elements of donuts1 = $donuts")

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

Step 3: How to initialize a Sequence of donuts
Elements of donuts1 = List(Plain, Strawberry, Glazed)

4. How to create a String of all donuts using foldLeft function

The code below shows how to create a String representation for all the donut elements in the Sequence and also append the word Donut to each element using the foldLeft method.

println("\nStep 4: How to create a String of all donuts using foldLeft function")
println(s"All donuts = ${donuts.foldLeft("")((a, b) => a + b + " Donut ")}")

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

Step 4: How to create a String of all donuts using foldLeft function
All donuts = Plain Donut Strawberry Donut Glazed Donut 

5. How to declare a value function to create the donut string

The code below shows how to declare a Value Function to encapsulate the behaviour for creating a String representation for all donut elements.

println("\nStep 5: How to declare a value function to create the donut string")
val concatDonuts: (String, String) => String = (a, b) => a + b + " Donut "
println(s"Value function concatDonuts = $concatDonuts")

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

Step 5: How to declare a value function to create the donut string
Value function concatDonuts = <function2>

6. How to create a String of all donuts using value function from Step 5 and foldLeft function

The code below shows how to create a String representation for the donut elements by passing through the Value Function from Step 5 to the foldLeft method.

println("\nStep 6: How to create a String of all donuts using value function from Step 5 and foldLeft function")
println(s"All donuts = ${donuts.foldLeft("")(concatDonuts)}")

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

Step 6: How to create a String of all donuts using value function from Step 5 and foldLeft function
All donuts = Plain Donut Strawberry Donut Glazed Donut