anchor.diff:  ;; (find-measurement-class :mol)
   ;; (find-measurement-class :cd)
   
  +
   (defun make-measurement (magnitude unit &optional (degree 0))
  +  "Crate a MEAUREMENT object of the specified MAGNITUDE representing a
  +scalar measurement of measurement unit UNIT. The scalar magnitude of
  +the measurement.
  +
  +Examples:
  +
  +  (make-measurement 1 :m)
  +  => #<METER 1 m {1006289003}>
  +
  + (make-measurement 1 :m -3)
  + => #<METER 1E-3 m {10062E90C3}>
  +
  +
  +See also: 
  +* `scalar-magnitude'
  +* `prefix-of'
  +* `rescale', `nrescale'
  +
  +Notes:
  +* Results are undefined if DEGREE represents a prefix not available
  +  to `find-prefix'"
     (declare (type real magnitude)
  -           (type class-designator unit))
  -  ;; note: consequences are undefined if DEGREE represents a prefix 
  +           (type measurement-class-designator unit))
  +  ;; note: results are undefined if DEGREE represents a prefix 
     ;; not indexed in %PREFIXES%
  -  (make-instance (find-measurement-class unit)
  -                 :magnitude magnitude
  -                 :degree degree))
  +  (make-instance  (etypecase unit
  +                    (symbol (find-measurement-class unit))
  +                    (measurement-class unit))
  +                  :magnitude magnitude
  +                  :degree degree))
   
   ;; (make-measurement 1 :m)
   
  
positive.code: ;; (measurement-print-name (make-measurement 1 :m))
  ;; => "m"
  
  (defun prefix-of (m)
    (declare (type measurement m)
             (values prefix))
    (let ((deg (measurement-degree m)))
  
negative.code: 
  
  
  ;;; % Geometry Domain
  
  
  (defclass scalar (measurement) ;; a monadic coordinate
    ())
  
  
  ;; (defclass plane ...)
  ;; (defclass space ...)
  ;;
  ;; The term "Coordinate" will be applied informaly, in the following
  ;;
  ;; (defclass diadic-coordinate ...) ;; a <point> onto a <planar surface>
  ;; (defclass triadic-coordinate ...) ;; a <point> onto <3 space>
  ;; (defclass polar-coordinate ...) 
  ;; ^ a <point> within a <polar coordinate> system  on a <planar surface>
  ;; (defclass spherical-coordinate ...)
  ;; ^ a <point> within a <spherical coordinate space>
  
  
  
  