+-- | Monads having fixed points with a \`knot-tying\' semantics.
+-- Instances of 'MonadFix' should satisfy the laws
+--
+-- [purity]
+-- @'mfix' ('return' . h) = 'return' ('fix' h)@
+--
+-- [left shrinking (or tightening)]
+-- @'mfix' (\x -> a >>= \y -> f x y) = \y -> 'mfix' (\x -> f x y)@
+--
+-- [sliding]
+-- @'mfix' ('Control.Monad.liftM' h . f) = 'Control.Monad.liftM' h ('mfix' (f . h))@,
+-- for strict @h@.
+--
+-- [nesting]
+-- @'mfix' (\x -> 'mfix' (\y -> f x y)) = 'mfix' (\x -> f x x)@
+--
+-- This class is used in the translation of the recursive @do@ notation
+-- supported by GHC and Hugs.