> To anticipate a common question: why couldn't my-unless be a function? Function arguments are evaluated eagerly, before the function ever sees them.

Interesting, so if you’re using a lazy language then you don’t need a macro here and could write my-unless as a function.

Remember the golden rule of Lisp macros: don't write a macro.

I always thought it odd that Penrose gets dropped from the Escher conversations.

If macros can implement arbitrary language features then how come elisp has never built a type system?