arnesi

def-special-environment 

(defun check-required (name vars required)
  (dolist (var required)
    (assert (member var vars)
            (var)
            "Unrecognized symbol ~S in ~S." var name)))

(defmacro def-special-enviroment (name (&key accessor binder binder*) &rest vars)
  "Define two macros for dealing with groups or related special variables.
[...]
ACCESSOR is defined as a macro: (defmacro ACCESSOR (VARS &rest
BODY)).  Each element of VARS will be bound to the
current (dynamic) value of the special variable.

BINDER is defined as a macro for introducing (and binding new)
special variables. It is basically a readable LET form with the
prorpe declarations appended to the body. The first argument to
BINDER must be a form suitable as the first argument to LET.

ACCESSOR defaults to a new symbol in the same package as NAME
which is the concatenation of \"WITH-\" NAME. BINDER is built as
\"BIND-\" and BINDER* is BINDER \"*\"."
  (unless accessor
    (setf accessor (intern-concat (list '#:with- name) (symbol-package name))))
  (unless binder
    (setf binder   (intern-concat (list '#:bind- name) (symbol-package name))))
  (unless binder*
    (setf binder*  (intern-concat (list binder '#:*) (symbol-package binder))))
  `(eval-when (:compile-toplevel :load-toplevel :execute)
     (flet ()
       (defmacro ,binder (requested-vars &body body)
         (check-required ',name ',vars (mapcar #'car requested-vars))
         `(let ,requested-vars
            (declare (special ,@(mapcar #'car requested-vars)))
            ,@body))
       (defmacro ,binder* (requested-vars &body body)
         (check-required ',name ',vars (mapcar #'car requested-vars))
         `(let* ,requested-vars
            (declare (special ,@(mapcar #'car requested-vars)))
            ,@body))
       (defmacro ,accessor (requested-vars &body body)
         (check-required ',name ',vars requested-vars)
         `(locally (declare (special ,@requested-vars))
            ,@body))
       ',name)))