+ (when (or (not focal-length) (not units)
+ (not (n-args-not-nil 1 original-object-distance
+ original-image-distance
+ original-magnification))
+ (not (n-args-not-nil 1 new-object-distance
+ new-image-distance
+ new-magnification
+ extension-length)))
+ (error "Invalid arguments.
+Must set 1 of the following original-object-distance, original-image-distance,
+or original-magnification parameters as well as one of the following parameters
+new-object-distance, new-image-distance, new-magnification, or extension-length."))
+
+ (flet ((ret (ood oid om obf nod nid nm nbf e)
+ (list :focal-length focal-length :original-object-distance ood
+ :original-image-distance oid :original-magnification om
+ :original-bellows-factor obf :new-object-distance nod
+ :new-image-distance nid :new-magnification nm
+ :new-bellows-factor nbf :extension-length e)))
+
+ (multiple-value-bind (focal-length-original o-od o-id o-m o-bf)