イテレータの反転をつかったパイプライン。

t.scm

(use gauche.generator)
(use text.tr)

(define (generator-inverter) 
  (^[produce consume] (consume (generate produce) ) ) )

(define (pipeline inverter cmd-in cmd-out)
  (^[ g yield]
    (inverter
      (^[yield]
        (cmd-in g yield) )
      (^g
        (cmd-out g yield) ) ) ) )

(define (cat)
  (^[g yield]
    (do-generator (f g)
      (call-with-input-file 
        f (^p (generator-for-each yield (cut read-line p) ) ) ) ) ) )

(define (tr from to)
  (^[g yield]
    (generator-for-each yield (gmap (cut string-tr <> from to) g) ) ) ) 

(define (grep rx)
  (^[g yield]
    (generator-for-each yield (gfilter rx g) ) ) )

(define c 
  (pipeline (generator-inverter) 
            (cat)
            (pipeline (generator-inverter) 
                      (grep #/define/)
                      (tr "a-z" "A-Z") ) ) )
(c ($ list->generator $ glob "*.scm" ) print)