Maybe, maybe not, but I had three criteria and C/C++ certainly don't meet the other two. (There are other criteria we use when making these kinds of decisions,

Maybe, maybe not, but I had three criteria and C/C++ certainly don't meet the other two. (There are other criteria we use when making these kinds of decisions, like performance, speed of development, availability of developers etc, but I thought we were talking about modern functional languages so I didn't bring these up.) I think the language that hasn't the biggest chance of upsetting the JVM is Rust. Mozilla talk about Rust as a C/C++ replacement, but I actually expect they'll see more interest from JVM focused developers. A lot of current systems programming uses the JVM (all the aforementioned big data systems like Kafka, Cassanda, HBase, etc.) A number of these systems have issues with the JVM, particularly GC performance on large heaps, and Rust would be very attractive here. Scala developers in particular are used to modern language idioms and so could relatively easily switch to Rust.