Interesting that it uses defun, like Common Lisp, the main Lisp-2 dialect, and yet it's clearly a Lisp-1, like Scheme. After (defun f (n) (+ n 1)), evaluating f shows that it's a function (just as in Python, which is a Lisp-1). My first thought, for what it's worth, is that if the namespace semantics is like Scheme it'd be better to follow Scheme idioms rather than Common Lisp, so code can be easily ported. On the other hand, this is only my first minute using Hy so what do I know. Looks really neat!