Response to https://gist.github.com/redline6561/5017627

cpu.lisp

(defmacro defenum (name (&rest keys))
  "Define a function named %NAME, that takes an argument KEY and returns
an associated value from KEYS.  If KEYS are scalar values, the associated
values are zero-based indices."
  (let ((function-name (intern (format nil "%~:@(~A~)" name))))
    (flet ((ensure-alist (list)
             (let ((i -1))
               (mapcar #'(lambda (x)
                           (destructuring-bind (key &optional (value (incf i)))
                               (alexandria:ensure-list x)
                             (cons key value)))
                       list))))
      (alexandria:with-unique-names (hash-table)
        `(let ((,hash-table (alexandria:alist-hash-table (ensure-alist ,keys))))
           (defun ,function-name (key)
             (gethash key ,hash-table))))))