7 Working with CSV files
In the last chapter, we tackled a search problem and wrote some powerful artificial intelligence for a children’s game. In this chapter, however, we want to take care of earnest business, and nothing screams business like spreadsheets! Don’t worry, we will not deal with any data directly. As programmers, we obviously want to automate such tasks, and the easiest way for us to deal with data in spreadsheet form is using comma-separated values (CSV) files.
In this chapter, we will cover how to parse such files, extract meaningful data from them, and work effectively with structured data. We will learn how to generalize the appending and slicing of data as well as how to bring type classes into the mix to help us write our program.
This chapter will begin with an introduction to CSV files and how to model them using Haskell’s record syntax. We will learn how to encode errors using the Either type. We will cover using the dollar operator and certain language extensions to simplify our syntax. Following this, we will create our own type classes to generalize the use case for our data types. All the while, we will learn about the type classes Semigroup and Monoid, what they represent, and what they are used for.