Steps

1. How to initialize a List of donuts

The code below shows how to create a List of donuts of type String.

println("Step 1: How to initialize a List of donuts")
val donuts: Seq[String] = List("Plain Donut", "Strawberry Donut", "Glazed Donut")
println(s"Elements of donuts = $donuts")

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

Step 1: How to initialize a List of donuts
Elements of donuts = List(Plain Donut, Strawberry Donut, Glazed Donut)

2. How to take elements from the List using the takeWhile function

The code below shows how to use the takeWhile method to take donut elements whose names start with letter P.

println("\nStep 2: How to take elements from the List using the takeWhile function")
println(s"Take donut elements which start with letter P = ${donuts.takeWhile(_.charAt(0) == 'P')}")

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

Step 2: How to take elements from the List using the takeWhile function
Take donut elements which start with letter P = List(Plain Donut)

3. How to declare a predicate function to be passed-through to the takeWhile function

Let's create a predicate function which will encapsulate the donut predicate of selecting donut elements whose names start with letter P.

println("\nStep 3: How to declare a predicate function to be passed-through to the takeWhile function")
val takeDonutPredicate: (String) => Boolean = (donutName) => donutName.charAt(0) == 'P'
println(s"Value function takeDonutPredicate = $takeDonutPredicate")

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

Step 3: How to declare a predicate function to be passed-through to the takeWhile function
Value function takeDonutPredicate = <function1>

4. How to take elements using the predicate function from Step 3

With the predicate function defined in Step 3, we can not pass it to the takeWhile function in order to take donut elements whose names start with letter P.

println("\nStep 4: How to take elements using the predicate function from Step 3")
println(s"Take elements using function from Step 3 = ${donuts.takeWhile(takeDonutPredicate)}")

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

Step 4: How to take elements using the predicate function from Step 3
Take elements using function from Step 3 = List(Plain Donut)