6.8.1. Multi-parameter type classes

MultiParamTypeClasses
Implies:ConstrainedClassMethods
Implied by:FunctionalDependencies
Since:6.8.1
Status:Included in GHC2021

Allow the definition of typeclasses with more than one parameter.

Multi-parameter type classes are permitted, with extension MultiParamTypeClasses. For example:

class Collection c a where
    union :: c a -> c a -> c a
    ...etc.