os-part function

(define (os-part inherit-list packages services)
  (if (null? inherit-list)
      (lambda () (list (cons packages-keyword packages)
                  (cons services-keyword services)))
      (lambda () (let ((inherited ((car inherit-list))))
              ((os-part (cdr inherit-list)
                        (append (or (assoc-ref inherited packages-keyword) #nil)
                                packages)
                        (append (or (assoc-ref inherited services-keyword) #nil)
                                services)))))))

;;;; example usage: no-desktop-environment.scm

(os-part (list
          ;; Other os-part files can be loaded here. ex.
          ;; (load "./other-os-part.scm")
          )
         (list
          compton
          slock
          gnome-icon-theme
          brightnessctl)
         (cons*
          (service
           slim-service-type
           (slim-configuration
            (xorg-configuration
             (xorg-configuration
              (extra-config '("
                         Section \"Device\"

                             Identifier \"Intel Graphics\"

                             Driver \"intel\"

                             Option \"TearFree\" \"false\"

                         EndSection
                         "))))))
          (remove
           (lambda (service)
             (eq? (service-kind service) gdm-service-type))
           (modify-services %desktop-services
             (udev-service-type
              config =>

              (udev-configuration
               (inherit config)
               (rules (cons brightnessctl
                            (udev-configuration-rules config)))))))))