Get set in Haskell

In Haskell, the get and set functions are used to access and modify fields of a record.

In order to demonstrate how to use get and set, let's create a simple example class called Person that has two fields: name and age.

data Person = Person { 
  name :: String,
  age :: Int
} deriving (Show)

Here, we have defined the Person class using the data keyword and defined two fields using the record syntax.

To access the name field of a Person object, we can use the name function as follows:

pName :: Person -> String
pName p = name p

This function takes a Person object as input and returns its name field.

To modify the name field of a Person object, we can use the set function as follows:

setName :: String -> Person -> Person
setName n p = p {name = n}

This function takes a String and a Person object as input, modifies the name field and returns the updated Person object.

Here's an example of how we would use these functions:

-- create a person
mike = Person {name = "Mike", age = 26}
-- get the person's name

mikeName = pName mike     -- returns "Mike"
-- set the person's name

mike' = setName "Michael" mike -- creates a new Person object with name "Michael" instead of "Mike"

Overall, the get and set functions in Haskell allow us to easily access and modify record fields, making it easy to work with complex data structures.