>I don't see how this is any knock against the functional programming paradigm. I always understood the rule of thumb to be "use purity as much as possible, and

>I don't see how this is any knock against the functional programming paradigm. I always understood the rule of thumb to be "use purity as much as possible, and be impure only when it's explicitly needed." Modifying a global state seems to be a pretty obvious case for using an impure function. This is pretty much exactly what he's saying. His response was targeted at people who think functional programs should wholly avoid state and side-effects. (I don't actually know of too many people who believe this, but apparently he does)