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Is it possible to see which typeclasses the type implements? Something like:
>:typeclasses Int [Num, etc...] 
527
Haskell will check all types at compile time, including membership of typeclasses. So to check if a literal is of a type that supports Eq, you simply need to use it with (==) or (/=) and try to compile it.
An instance of a class is an individual object which belongs to that class. In Haskell, the class system is (roughly speaking) a way to group similar types. (This is the reason we call them "type classes"). An instance of a class is an individual type which belongs to that class.
We say that Eq is a superclass of Ord (conversely, Ord is a subclass of Eq), and any type which is an instance of Ord must also be an instance of Eq.
Type classes define interfaces that in Haskell's terms are called dictionaries. For instance, from the Ord class definition the compiler will create a dictionary that stores all the class methods.
Use the :info command.
Prelude> :info Int data Int = GHC.Types.I# GHC.Prim.Int# -- Defined in GHC.Types instance Bounded Int -- Defined in GHC.Enum instance Enum Int -- Defined in GHC.Enum instance Eq Int -- Defined in GHC.Base instance Integral Int -- Defined in GHC.Real instance Num Int -- Defined in GHC.Num instance Ord Int -- Defined in GHC.Base instance Read Int -- Defined in GHC.Read instance Real Int -- Defined in GHC.Real instance Show Int -- Defined in GHC.Show Naturally this list depends on the modules that are currently imported.
Prelude> :info (->) data (->) a b -- Defined in GHC.Prim Prelude> :m +Control.Monad.Instances Prelude Control.Monad.Instances> :info (->) data (->) a b -- Defined in GHC.Prim instance Monad ((->) r) -- Defined in Control.Monad.Instances instance Functor ((->) r) -- Defined in Control.Monad.Instances If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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