Monads are used for abstracting computation composition. In any given Haskell code, I'd say at least 80% of my monadic code is non-imperative. There are imperat

Monads are used for abstracting computation composition. In any given Haskell code, I'd say at least 80% of my monadic code is non-imperative. There are imperative monads (ST, IO), but also many many functional ones. I've written an introductory article at < http://ianen.org/articles/monad-is-not-difficult/ http://ianen.org/articles/monad-is-not-difficult/ >. The first example in the article demonstrates what I mean by "computation composition". "mdiv(2.0, 3.0)" returns a Maybe, not a float, and before using it as a float the inner value must be unpacked. That can be done without the monad operators, but is verbose and error-prone: mdiv :: Float -> Float -> Float mdiv a b = if b == 0 then Nothing else Just (a / b) with_maybe :: Maybe Float with_maybe = case mdiv 2.0 2.0 of Nothing -> Nothing Just val1 -> case mdiv 3.0 0.0 of Nothing -> Nothing Just val2 -> case mdiv val1 val2 of Nothing -> Nothing Just val3 -> Just val3 Here's that same example, rewritten to use the monadic operators (with explicit lambdas, as in the article): with_maybe :: Maybe Float with_maybe = mdiv 2.0 2.0 >>= (\val1 -> mdiv 3.0 0.0 >>= (\val2 -> mdiv val1 val2 >>= (\val3 -> Just val3))) And, for completeness, using Haskell's lambda-hiding 'do' notation: with_maybe :: Maybe Float with_maybe = do val1 <- mdiv 2.0 2.0 val2 <- mdiv 3.0 0.0 val3 <- mdiv val1 val2 Just val3