Types and Typeclasses

Types and Typeclasses

1. Use the data keyword to define a type

2. Value constructors are actually functions that return a value of a data type

3. You can export your data types in your modules: Shape(..)

4. Record syntax

   • data Person = Person { firstName :: String , ...

5. Type parameters

   • We use them when our data type would work regardless of the type of the value it then holds inside it

6. Typeclass is a sort of an interface that defines some behavior

7. Derived instances

   • A type is an instance of a typeclass if the type has the behavior of the typeclass

8. Type synonyms

   • They're just about giving some types different names
   • Just like we call a function with too few parameters to get back a new function, we can specify a type constructor with too few type parameters and get back a partially applied type constructor.

9. A typeclass is a sort of an interface that defines some behavior

10. Recursive data structures

    • We can make types whose constructors have fields that are of the same type

11. Types

    • data Bool = False | True
      • type = The different values that this type can have
    • if we add deriving (Show) at the end of a data declaration, that type become part of the Show typeclass
      • data Shape ...|... deriving (Show)
    • Intermediate data type
      • data Point = Point Float Float data Shape = Circle Point Float

12. Typeclass

    • A typeclass defines some behavior like comparing for equality and then types that can behave in that way are made instances of that typeclass
    • class Eq a where...