http://togetter.com/li/669552

callcc-promise.scm

(import (scheme lazy)
	(picrin macro))

(define-syntax delay/cc
  (syntax-rules ()
    ((delay/cc expr)
     (lambda (k) (k expr)))))

(define-syntax force/cc
  (syntax-rules ()
    ((force/cc expr)
     (call/cc expr))))

(define pr1 (delay (+ 1 2)))
(define pr2 (delay/cc (+ 1 2)))

(= (+ 3 (force pr1)) (+ 3 (force/cc pr2)))
; => #t

(macroexpand '(force/cc (delay/cc (+ 1 2))))
; => (call/cc@142 (lambda (k@1744) (k@1744 (+@77 1 2))))