Comment by gmfawcett

In fairness, we could be in the List monad here, and this would effectively be a list comprehension rather than an imperative program. Even if we are in IO, `getPrices` and `book` may never execute --- even `finishDeal` may never execute! --- depending on non-local details that aren't shown here.

The code certainly "looks imperative" but it's still a declarative program --- the semantics are rather different from what a typical "imperative programmer" would expect.