Remove scheme-lib/lazy.scm

scheme-lib/lazy.scm

@@ -1,47 +0,0 @@
-; SRFI 45: Primitives for Expressing Iterative Lazy Algorithms
-; by André van Tonder
-;=========================================================================
-; Boxes
-
-(define (box x) (list x))
-(define unbox car)
-(define set-box! set-car!)
-
-;=========================================================================
-; Primitives for lazy evaluation:
-
-(define (eager x)
-  (box (cons 'eager x)))
-
-#|
-(define-syntax lazy
-  (syntax-rules ()
-    ((lazy exp)
-     (box (cons 'lazy (lambda () exp))))))
-
-(define-syntax delay
-  (syntax-rules ()
-    ((delay exp) (lazy (eager exp)))))
-|#
-
-(define-macro (lazy exp)
-  `(box (cons 'lazy (lambda () ,exp))))
-
-(define-macro (delay exp)
-  `(lazy (eager ,exp)))
-
-(define (force promise)
-  (let ((content (unbox promise)))
-    (case (car content)
-      ((eager) (cdr content))
-      ((lazy)  (let* ((promise* ((cdr content)))
-                      (content  (unbox promise)))                      ; *
-                 (if (not (eqv? (car content) 'eager))                 ; *
-                     (begin (set-car! content (car (unbox promise*)))
-                            (set-cdr! content (cdr (unbox promise*)))
-                            (set-box! promise* content)))
-                 (force promise))))))
-
-; (*) These two lines re-fetch and check the original promise in case
-;     the first line of the let* caused it to be forced.  For an example
-;     where this happens, see reentrancy test 3 below.