prop_assoc :: ArbMapSyntax String Int
              -> ArbMapSyntax String Int
              -> ArbMapSyntax String Int
              -> Bool
prop_assoc a' b' c' =
    runMap ((a `mappend` b) `mappend` c) ==
    runMap (a `mappend` (b `mappend` c))
  where a = unArbSyntax a'
        b = unArbSyntax b'
        c = unArbSyntax c'
prop_assoc :: ArbMapSyntax String Int
              -> ArbMapSyntax String Int
              -> ArbMapSyntax String Int
              -> Bool
prop_assoc a' b' c' =
    runMap ((a `mappend` b) `mappend` c) ==
    runMap (a `mappend` (b `mappend` c))
  where a = unArbSyntax a'
        b = unArbSyntax b'
        c = unArbSyntax c'
prop_assoc a' b' c' =
    runMap ((a `mappend` b) `mappend` c) ==
    runMap (a `mappend` (b `mappend` c))
  where a = unArbSyntax a'
        b = unArbSyntax b'
        c = unArbSyntax c'