chapter thirty

30 Working with List: Element selection

 

After reading this lesson, you will be able to

Select the first element of a sequence

Pick the nth item of a list

Find the first element of a sequence that respects a given predicate

Find the minimum/maximum item in a list according to some criteria

In the previous lesson, you learned how to analyze the properties of a sequence. In this lesson, you’ll discover how to select one item in a list by its position. You’ll also learn how to find an item that has specific characteristics. Finally, you’ll see how to select the minimum or maximum element in a list based on natural ordering or custom ordering criteria. In the capstone, you’ll analyze the movies data set to determine which movie has the highest profit.

Consider this

You have a list of exam scores. How will you find the highest and the lowest ones?

30.1 Selecting an element by its position

Let’s continue to expand the functionalities of your address book program.

Listing 30.1 Representation of a contact
case class Contact(name: String,
                   surname: String,
                   numbers: List[ContactNumber],
                   company: Option[String],
                   email: Option[String])
 
sealed trait Label
case object Work extends Label
case object Home extends Label
 
case class ContactNumber(number: String, label: Label)

Imagine you now need to select a contact based on its position in you address book.

30.2 Finding an element with given features

30.3 Picking the minimum or maximum item

Summary

Answers to quick checks