Data commit

Task/Metered-concurrency/Racket/metered-concurrency.rkt

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+#lang racket
+
+(define sema (make-semaphore 4)) ; allow 4 concurrent jobs
+
+;; start 20 jobs and wait for all of them to end
+(for-each
+ thread-wait
+ (for/list ([i 20])
+   (thread (λ() (semaphore-wait sema)
+                (printf "Job #~a acquired semaphore\n" i)
+                (sleep 2)
+                (printf "Job #~a done\n" i)
+                (semaphore-post sema)))))