Comment by Kodiologist

Admittedly, I've tried not to document the implementation. Yeah, they're pretty much simple dirty Common Lisp macros. Internally, they're functions that are called with the arguments converted to models (via `hy.as-model`), and then the return value is converted to a model. If a macro's first parameter is named `_hy_compiler`, it gets access to the current compiler object; this is undocumented since it's only meant for internal use. Reader macros have no parameters, but can access the current reader object as `&reader`. When it's defined, a reader macro is added to the current reader's dispatch table.