;; environment.lq

(define (environment-all-names env)
  (let ((parent (environment-parent env)))
    (if parent
        (unique (append (environment-names env)
                        (environment-all-names parent))
                equal?)
        (environment-names env))))

(define (environment-set! env name value)
  (let ((z (environment-lookup env name)))
    (if z
        (let# (penv old-value) z
          (environment-bind! penv name value))
        (error "environment-set!: name does not exist"))))