fundamentals-fp-lab3.md

Lab3

Learning objective: To create and use custom data types and type-classes

Prerequisite

1. Daml SDK installed and setup
2. Daml Fundamentals Training: Functional Programming in Daml - Lessons 1 to 8 completed.

Problem statement 1

This problem has two parts

1. Create a data type called Person that has two fields - name and email - both of type Text. Make Person an instance of Show, Eq, and Ord. Then test it out using the following test script:

   testPerson = script do 
       let 
           person1 = Person with 
               name = "Alice"
               email = "alice@earth.com"
       
           person2 = Person with 
               name = "Bob"
               email = "bob@earth.com"
   
       debug person1
       debug $ person1 == person2
       debug $ person1 < person2
       return ()
   

   The testPerson Script should yield the result shown below:

   Trace: 
   Person {name = "Alice", email = "alice@earth.com"}
   False
   True
   

2. Create a type class named Reachable that has a function named reachOut. Make the Person data type defined above an instance of Reachable. The reachOut function takes a record of Person type as an input and returns a text string that uses the Person's name and email. For example, if a Person record has name as "Alice" and email as "alice@earth.com", then reachOut function should return:

"Hello Alice at alice@earth.com"

Here is the script to test your code:

testReachable = script do
    let
        myFriend = Person with 
            name = "Alice"
            email = "alice@earth.com"

        message: Text =  reachOut myFriend

    debug $ message

And here is the expected output

Trace: 
  "Hello Alice at alice@earth.com"