Data commit

Task/Mutex/Racket/mutex-1.rkt

@@ -0,0 +1,6 @@
+(define foo
+  (let ([sema (make-semaphore 1)])
+    (lambda (x)
+      (dynamic-wind (λ() (semaphore-wait sema))
+                    (λ() (... do something ...))
+                    (λ() (semaphore-post sema))))))

Task/Mutex/Racket/mutex-2.rkt

@@ -0,0 +1,10 @@
+(define-syntax-rule (define/atomic (name arg ...) E ...)
+  (define name
+    (let ([sema (make-semaphore 1)])
+      (lambda (arg ...)
+        (dynamic-wind (λ() (semaphore-wait sema))
+                      (λ() E ...)
+                      (λ() (semaphore-post sema)))))))
+;; this does the same as the above now:
+(define/atomic (foo x)
+  (... do something ...))