Language.Haskell.TH.Instances

Documentation

instances :: QuasiQuoter

QuasiQuoter for providing intrinsic-superclasses.

Example:

 class Semigroup a where mappend :: a -> a -> a
 class Semigroup a => Commutative a
 class Semigroup a => Monoid a where mempty :: a
 class Monoid a => Group a where inverse :: a -> a
 class (Commutative a, Group a) => CommutativeGroup a
 [instances| Num a => CommutativeGroup a where
     mempty = fromInteger 0
     mappend a b = a + b
     inverse = negate
     |]

will generate the appropriate instances for Semigroup, Monoid, and Group:

 instance Num a => Semigroup a where mappend a b = a + b
 instance Num a => Commutative a
 instance Num a => Monoid a where mempty = fromInteger 0
 instance Num a => Group a where inverse = negate
 instance Num a => CommutativeGroup a