anchor.diff:                                            0.125))
                               :length length))))
   
  -(defmethod as-pstream ((pbrown pbrown))
  -  (with-slots (lo hi step length) pbrown
  -    (make-instance 'pbrown-pstream
  -                   :lo (pattern-as-pstream lo)
  -                   :hi (pattern-as-pstream hi)
  -                   :step (pattern-as-pstream step)
  -                   :length (as-pstream length))))
  -
   (defmethod next ((pbrown pbrown-pstream))
     (unless (remaining-p pbrown 'length)
       (return-from next eop))
  
positive.code: ;; ;=> (1 3 5 7)
  
  See also: `pseries*', `pgeom', `paccum'")
  
  (defmethod as-pstream ((pseries pseries))
    (with-slots (start step length) pseries
      (make-instance 'pseries-pstream
                     :start (pattern-as-pstream start)
                     :step (pattern-as-pstream step)
                     :length (as-pstream length))))
  
  (defmethod next ((pseries pseries-pstream))
    (with-slots (start step current-value) pseries
  
negative.code: ;; ;=> (1 2 4 8)
  
  See also: `pseries', `paccum'")
  
  (defmethod next ((pgeom pgeom-pstream))
    (with-slots (start grow current-value) pgeom
  