I think the author was fairly careful in drawing a distinction between functional programming and programming in the functional style. You can get a lot of mil

I think the author was fairly careful in drawing a distinction between functional programming and programming in the functional style. You can get a lot of mileage from writing pure functions and using immutable state regardless of what language you're in. It doesn't make your language a functional programming language, nor does it make you a functional programmer, but does that matter? If every pure function we write prevents another headache, why not seek out opportunities to write in that style, regardless of language?