nested-set! (current-module) name val
;;;     local-define name val         ==  nested-define! (current-module) name val
;;;     local-remove name             ==  nested-remove! (current-module) name
;;;     local-ref-module name         ==  nested-ref-module (current-module) name
;;;     local-define-module! name m   ==  nested-define-module! (current-module) name m
;;;


(define (nested-ref root names)
  (if (null? names)
      root
      (let loop ((cur root)
                 (head (car names))
                 (tail (cdr names)))
        (if (null? tail)
            (module-ref cur head #f)
            (let ((cur (module-ref-submodule cur head)))
              (and cur
                   (loop cur (car tail) (cdr tail))))))))

(define (nested-set! root names val)
  (let loop ((cur root)
             (head (car names))
             (tail (cdr names)))
    (if (null? tail)
        (module-set! cur head val)
        (let ((cur (module-ref-submodule cur head)))
          (if (not cur)
              (error "failed to resolve module" names)
              (loop cur (car tail) (cdr tail)))))))

(define (nested-define! root names val)
  (let loop ((cur root)
             (head (car names))
             (tail (cdr names)))
    (if (null? tail)
        (module-define! cur head val)
        (let ((cur (module-ref-submodule cur head)))
          (if (not cur)
              (error "failed to resolve module" names)
              (loop cur (car tail) (cdr tail)))))))

(define (nested-remove! root names)
  (let loop ((cur root)
             (head (car names))
             (tail (cdr names)))
    (if (null? tail)
        (module-remove! cur head)
        (let ((cur (module-ref-submodule cur head)))
          (if (not cur)
              (error "failed to resolve module" names)
              (loop cur (car tail) (cdr tail)))))))


(define (nested-ref-module root names)
  (let loop ((cur root)
             (names names))
    (if (null? names)
        cur
        (let ((cur (module-ref-submodule cur (car names))))
          (and cur
               (loop cur (cdr names)))))))

(define (nested-define-module! root names module)
  (if (null? names)
      (error "can't redefine root module" root module)
      (let loop ((cur root)
                 (head (car names))
                 (tail (cdr names)))
        (if (null? tail)
            (module-define-submodule! cur head module)
            (let ((cur (or (module-ref-submodule cur head)
                           (let ((m (make-module)))
                             (set-module-kind! m 'directory)
                             (set-module-name! m (append (module-name cur)
                                                         (list head)))
                             (module-define-submodule! cur head m)
                             m))))
              (loop cur (car tail) (cdr tail)))))))


(define (local-ref names)
  (nested-ref (current-module) names))

(define (local-set! names val)
  (nested-set! (current-module) names val))

(define (local-define names val)
  (nested-define! (current-module) names val))

(define (local-remove names)
  (nested-remove! (current-module) names))

(define (local-ref-module names)
  (nested-ref-module (current-module) names))

(define (local-define-module names mod)
  (nested-define-module! (current-module) names mod))