Monoid

A subclass of Semigroup

Minimal Complete Definition

class Monoid a  
  where
    (<>) :: a -> a -> a
    mempty :: a

Methods

class Monoid a  
  where
    (<>) :: a -> a -> a
    mempty :: a
    mconcat :: [a] -> a

• <> defines composability (identical to Semigroup)
• mempty : the identity element
• mconcat: apply <> to a multiple times.

Type Class Laws

• associativity: (a <> b) <> c == a <> (b <> c).
• identity: a <> mempty = a & mempty a = a