[chongli]

Haskell is not imperative, though it allows you to express imperative programs within it via Monads. One way to think of Haskell is as a purely functional, lazy analogue to the C Preprocessor. Your program is then merely a function whose value is a set of instructions for performing the effects you desire on some particular machine. The cool thing about being lazy in this context is that preprocessing time (evaluation of the function) and runtime are interleaved rather than separate (as in the case of C).