{-# RULES
"++" xs ++ ys = augment (\c n -> foldr c n xs) ys
"concat" xs `concat` ys = augment (\c n -> foldr c n xs) ys
  #-}

{-# RULES
"++" xs ++ ys = augment (\c n -> foldr c n xs) ys;
"concat" xs `concat` ys = augment (\c n -> foldr c n xs) ys;
"map/Double" fmap f xs = foldr (++) f xs
  #-}

{-# RULES
    "fb' >\\ (Request b' fb )" forall fb' b' fb  .
        fb' >\\ (Request b' fb ) = fb' b' >>= \b -> fb' >\\ fb  b;
#-}