problem-os-interface.lisp

;; POSIX-based API. Really long and yuck.
(defn capitalize-file (path)
  ; Read the input.
  (def in-fd (open path))
  (def in-str (read in-fd))
  (close in-fd)
  ; Process the input.
  (def out-str (toupper in-str))
  ; Write the output.
  (def out-fd (open path 'w))
  (write out-fd out-str)
  (close out-fd))

;; with-x pattern. This is what Python does (if you're doing it right).
(defn capitalize-file (path)
  (def in-str
    (with-file (f path)
      (read f)))
  (def out-str (toupper in-str))
  (with-file (f path)
    (write f out-str)))

;; High-level-only approach. Potential problem: this doesn't let you
;; generically use non-file IO resources (e.g. stdio and sockets).
(defun capitalize-file [path]
  (->>
    (read-file path)
    toupper
    (write-file path)))

;; Something else?