We have released Exanoke, a pure functional language which is syntactically restricted to expressing the primitive recursive functions.
If this doesn't sound like a stellar achievement, it's probably because
it's not one. But, I was previously aware of only how an imperative
language could be restricted to primitive recursion (i.e. have only
loops) and previously did some work on analyzing functions in a
pure functional language to determine if they are primitive recursive
or not; in a way, Exanoke combines both of those ideas.