Two threads of execution example

concurrentreadandprint.rkt

@@ -0,0 +1,51 @@
+#lang racket
+;; author: Ibrahim Mkusa
+;; about: print and read concurrently
+
+;; reads values continously from stdin and redisplays them
+(define (read-loop)
+  (display (read-line))
+  (display "\n")
+  (read-loop)
+  )
+
+(define input-prompt "input: ")
+(define output-prompt "output: ")
+
+;; prompt for username and bind to a variable username
+(display "What's your name?\n")
+(define username (read-line))
+(define usernamei (string-append username ": ")) ;; make username appear nicer in a prompt
+(define fair (make-semaphore 1))
+
+;; intelligent read, quits when user types in "quit"
+(define (read-loop-i)
+  (display usernamei)
+  
+  (semaphore-wait fair)
+  (define input (read-line))
+  ;; do something over here with input maybe send it out
+  (cond ((string=? input "quit") (exit)))
+  (display (string-append output-prompt input "\n"))
+  (semaphore-post fair)
+  (read-loop-i)
+  )
+
+
+;; print hello world continously
+(define (hello-world)
+  (semaphore-wait fair)
+  (display "Hello, World!\n")
+  (semaphore-post fair)
+  (hello-world))
+
+(define t (thread (lambda ()
+                    (read-loop-i))))
+(define a (thread (lambda ()
+                    (hello-world))))
+;; below doesn't execute
+; (sleep 10)
+; (kill-thread t)
+; (define a (thread (display "hello world!\n")))
+; (display "John: hello soso\n")
+; (display "Emmanuel: cumbaya!!!!\n")