chickadee » transducers » reader-fold

Fold operation over reader procedures / generators. Can be used with transduce in the following way:

 
(import (chicken port)
        transducers)

(with-input-from-string "abcd"
  (lambda ()
    (transduce reader-fold
               values
               (collect-list)
               read-char)))

; => (#\a #\b #\c #\d)

To note: (take n) is not greedy / over-eager, so it is possible to read from a reader / generator and continue to read from the same port afterwards:

 
(import (chicken port)
        transducers
        test)

(with-input-from-string "abcd"
  (lambda ()
    (test "List is (a b)"
          (list #\a #\b)
          (transduce reader-fold
                     (take 2)
                     (collect-list)
                     read-char))

    (test "Reader has not yet read #\c"
          #\c
          (read-char)))