> Except that there is a real advantage to using pure functional programming That's only true for certain values of "real". In real "real" terms, the advantage

> Except that there is a real advantage to using pure functional programming That's only true for certain values of "real". In real "real" terms, the advantage is purely virtual - even very simple programs require hundreds of pages of proof. In effect, formal proofs are almost never done in real reality and the "advantage" remains purely virtual. > what's new about it (privileging the first argument of each procedure Multimethods, CLOS, Dylan? > inheritance Don't use it if you don't like it that much... > lots of hidden mutable state It's not hidden, it's encapsulated. Do you know Smalltalk? If not, you should try learning it; I liked Pharo very much. Look at Morphic, work with it for a while and you'll see the difference. You can also try devising purely functional equivalent of Morphic while you're at it (good luck!).