anchor.diff:  
   (defun map-reduce (reducer mapper sequence)
     "
  -MAP-REDUCE is suitable for only the case that MAPPER's cost is much expensive.
  - (QUICKSEARCH uses this function for drakma:http-request)
  -For each element in SEQUENCE (as an argument), MAPPER is computed with each thread,
  -then the results are collected by REDUCER.
  +MAP-REDUCE is suitable for only the case that `mapper''s cost is much
  +expensive (e.g. QUICKSEARCH invokes DRAKMA:HTTP-REQUEST as `mapper').
  +For each element in `sequence' (as an argument), `mapper' is computed it
  +with each thread, then the results are collected by `reducer'.
   
   Examples: (inefficient but intuitive)
   
  
positive.code:               :cache-size 10
                :threading? nil
                :quicklisp-verbose? t)"
    (let ((result nil))
      (if (not (or max-cols-supplied?  max-repos-supplied?
                   cache-size-supplied? clear-cache-supplied?
  
negative.code:     (when (and ?web *threading?* bordeaux-threads:*supports-threads-p*)
        ;; MAP Phase:
        ;; (Strictly, the following is not the MapReduce,
        ;;  but abstract model is the same if threads are equated with
        ;;  worker nodes.)
        (let ((drakma:*drakma-default-external-format* :utf-8))
          ;; (print 'threading) ;for DBG
          (loop :for space   :in '(cliki github bitbucket)
  