diff options
| -rw-r--r-- | libraries/base/Data/Monoid.hs | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/libraries/base/Data/Monoid.hs b/libraries/base/Data/Monoid.hs index a0e3b20eff..65e3bb76d7 100644 --- a/libraries/base/Data/Monoid.hs +++ b/libraries/base/Data/Monoid.hs @@ -40,7 +40,17 @@ import Test.QuickCheck -- --------------------------------------------------------------------------- -- | The class of monoids (types with an associative binary operation that --- has an identity). The method names refer to the monoid of lists, +-- has an identity). Instances should satisfy the following laws: +-- +-- * @mempty `mappend` x = x@ +-- +-- * @x `mappend` mempty = x@ +-- +-- * @x `mappend` (y `mappend` z) = (x `mappend` y) `mappend` z@ +-- +-- * @mconcat = 'foldr' mappend mempty@ +-- +-- The method names refer to the monoid of lists under concatenation, -- but there are many other instances. -- -- Minimal complete definition: 'mempty' and 'mappend'. |