If you want inscrutable Haskell you should go with the <$> operators :) I'd personally still rather have a vvs.reduce(env){|env, (a,b)| M.insert(a, b, env)

If you want inscrutable Haskell you should go with the <$> operators :) I'd personally still rather have a vvs.reduce(env){|env, (a,b)| M.insert(a, b, env)} but the for loop is perfectly readable also because it fits on a single line. I think for longer bodied reduces I might prefer a for loop actually.