Common Lisp has a very sophisticated type system. The only thing it doesn't have (among things that are currently fashionable) is compile-time typing by defaul

Common Lisp has a very sophisticated type system. The only thing it doesn't have (among things that are currently fashionable) is compile-time typing by default. Peridot is "novel" in that it introduces user-level compiler optimizations into a language that does have compile-time typing by default. But that's kind of like Chevrolet making a plug-in hybrid version of the C8 Corvette (which they recently announced they are going to do). Neither the C8 nor plug-in hybrids are new. A plug-in hybrid C8 will be new, and when it happens it will be a Big Deal to a niche market: the intersection of C8 fans and plug-in-hybrid fans. But it won't change the world. (For the record, I happen to be a member of the niche market to which a plug-in hybrid C8 will appeal, so I am very excited about it. So I get that some people may be excited about Peridot. I just think it's important to keep things in perspective.)