> If a company hires software engineers, there’s a good chance that critical parts of their business exist in the form of computer code. Therefore the growth of

> If a company hires software engineers, there’s a good chance that critical parts of their business exist in the form of computer code. Therefore the growth of that business is closely linked to the maintainability of that code. Businesses adapt and grow constantly, they perpetually change. New features and new offerings to customers are added every day. Existing features are revisited, strategies are revised, whole business models are pivoted. There are advantages to functional programs, but I wouldn't say they're any easier to change than imperative programs. In fact, it's often more work to change a program where all functions depend purely on their arguments. Instead of adding a single imperative state update, you have to add a new argument to a whole group of functions and thread state through them appropriately. Patterns like monads and monad transformers can make this easier, but massive stacks of monad transformers have their own issues (http://blog.ezyang.com/2013/09/if-youre-using-lift-youre-doing-it-wrong-probably/ http://blog.ezyang.com/2013/09/if-youre-using-lift-youre-doi...). (And besides, most functional programming languages apart from Haskell support mutable state (e.g. ML ref cells, Scheme set!) -- pure functions aren't fundamental to the functional paradigm.)