> pure functions always do exactly the same thing Unless there's a hardware error, OS error, language bug or any of the number of other circumstances which can

> pure functions always do exactly the same thing Unless there's a hardware error, OS error, language bug or any of the number of other circumstances which can messes up your assumptions. As Joe Armstrong said, you can't type-check being hit by a lightning, not to mention your pure function may never terminate simply because the thread it ran on was killed. > Language error-proneness is directly proportional Citation needed (and it doesn't matter to what exactly you think it's proportional at this point). A large-scale, confirmed independently a couple of times, academic study would do. In other words: it's not that simple, even if you choose to ignore performance. Immutable data and pure functions are great and should be used wherever it makes sense, but they are not a silver bullet.