Chapter 8 - Making Our Own Types and Typeclasses

Chapter 8 - Making Our Own Types and Typeclasses

1. We can create our own data types, it could be usefull for store diferent types of data in the same typeclass

   • Syntaxis
     • data <name of typeclass>
     • =
     • Data constructor or class definition

2. Record syntax

   • It is used as an alternative to define data types
   • data Person = Person { firstName :: String , lastName :: String , age :: Int }

3. Type parameters

   • A value constructor can take some values parameters and then produce a new value.
   • data Maybe a = Nothing | Just a

4. Derived instances

   • This works like inheritance in programming languages, the class takes attributes from parent class.
   • data Person = Person { firstName :: String , lastName :: String , age :: Int } deriving (Eq)

5. Type synonyms

   • type String = [Char]
   • Give equivalence between different types

6. Recursive data structures

   • This data structures, allow to store the same data type into same
   • data List a = Empty | Cons a (List a) deriving (Show, Read, Eq, Ord)

7. A yes-no typeclass

   • This type of class define a data as boolean like "" or [] in javascript
   • instance YesNo Int where yesno 0 = False yesno _ = True

8. Functor typeclass

   • This class is used for map classes that can be maped like lists
   • class Functor f where fmap :: (a -> b) -> f a -> f b