Write You a Haskell Stephen Diehl

Typeclass Declarations
Typeclass declarations consist simply of the list of typeclass constraints, the name of the class, and the
type variable ( single parameter only ). e body of the class is simply a sequence of scoped FunDecl
declarations with only the matchType field.
class [context] => classname [var] where
[body]
Consider a very simplified Num class.
class Num a where
plus :: a -> a -> a
ClassDecl
[]
(Name ”Num”)
[ Name ”a” ]
[ FunDecl
BindGroup
{ _matchName = Name ”plus”
, _matchPats = []
, _matchType =
Just
(Forall
[]
[]
(TArr
(TVar TV { tvName = Name ”a” })
(TArr
(TVar TV { tvName = Name ”a” })
(TVar TV { tvName = Name ”a” }))))
, _matchWhere = []
}
]
Typeclass instances follow the same pattern, they are simply the collection of instance constraints, the
name of name of the typeclass, and the head of the type class instance type. e declarations are a
sequence of FunDecl objects with the bodies of the functions for each of the overloaded function implementations.
instance [context] => head where
[body]
For example:
123