gistfile1.scm

(use gauche.threads)

(define (runonce fn)
  (let1 state (atom #f) ; once run, becomes (list result)
    (values (^[] (atomic state boolean))         ;has-run?
            (^[] (atomic-update! state (^_ #f))) ;reset
            (^ args                              ;once
              (car (atomic-update! state (^p (or p `(,(apply fn args))))))))))