Data commit

Task/Synchronous-concurrency/Ol/synchronous-concurrency.ol

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+(import (owl parse))
+
+(coroutine 'reader (lambda ()
+   ; lazy line-by-line file reader
+   (define (not-a-newline x) (not (eq? x #\newline)))
+   (define parser (let-parse*
+                        ((line (greedy* (byte-if not-a-newline)))
+                         (newline (imm #\newline)))
+                     (bytes->string line)))
+   (define file (file->bytestream "input.txt"))
+
+   (let loop ((in (try-parse parser file #false)))
+      (cond
+         ((not in) ; file is ended
+            (define envelope (wait-mail)) ; wait for a request
+            (mail (ref envelope 1) #eof)) ; send an end-of-file to caller
+         ((pair? in) ; new line is read
+            (define envelope (wait-mail)) ; wait for a request
+            (mail (ref envelope 1) (car in)) ; send a line to caller
+            (loop (try-parse parser (cdr in) #false)))
+         (else ; just a lazy read, let's repeat
+            (loop (force in)))))
+
+   (print "total lines read: " (await (mail 'writer #t)))
+))
+
+(coroutine 'writer (lambda ()
+   (let loop ((n 0))
+      (define line (await (mail 'reader #t)))
+
+      (if (eof? line)
+      then
+         (define envelope (wait-mail)) ; wait for a request
+         (mail (ref envelope 1) n) ; send a lines count to caller
+      else
+         (print "read line: " line)
+         (loop (+ n 1))))))