Hierarchical packages using user-extensible packages

hierarchical-packages.lisp

(in-package :cl-user)

(defstruct (hierarchical-package (:include sb-package:standard-package)))

(defmethod sb-package:find-package (package-designator (package hierarchical-package))
  (flet ((find-package-from-string (string)
           (when (and (> (length string) 0)
                      (char= (elt string 0) #\.))
             (setq string (concatenate 'string (package-name package) string)))
           (call-next-method string package)))
    (typecase package-designator
      (package package-designator)
      (symbol (find-package-from-string (symbol-name package-designator)))
      (string (find-package-from-string package-designator))
      (character (find-package-from-string (string package-designator)))
      (t (error 'type-error
                :datum package-designator
                :expected-type '(or character package string symbol))))))

(let ((package (make-hierarchical-package
                :%name "FOO"
                :internal-symbols (sb-impl::make-or-remake-package-hashtable 10)
                :external-symbols (sb-impl::make-or-remake-package-hashtable 10))))
  (sb-impl::initialize-package package :use '(:cl)))

(defpackage :foo.bar (:use :cl))

(setq *package* (find-package :foo))

(print (find-package :.bar))

(print (.bar::+ 1 2))