Problem Statement

The goal of this task is to create a counting semaphore used to control the execution of a set of concurrent units. This task intends to demonstrate coordination of active concurrent units through the use of a passive concurrent unit. The operations for a counting semaphore are acquire, release, and count. Each active concurrent unit should attempt to acquire the counting semaphore before executing its assigned duties. In this case the active concurrent unit should report that it has acquired the semaphore. It should sleep for 2 seconds and then release the semaphore.

Let's start with the solution:

import: parallel

Object Class new: Semaphore(ch)

Semaphore method: initialize(n)
   Channel newSize(n) dup := ch
   #[ 1 over send drop ] times(n) drop ;

Semaphore method: acquire  @ch receive drop ;
Semaphore method: release  1 @ch send drop ;

: mytask(s)
   while( true ) [
      s acquire "Semaphore acquired" .cr 
      2000 sleep
      s release "Semaphore released" .cr
      ] ;

: test(n)
| s i |
   Semaphore new(n) ->s     
   10 loop: i [ #[ s mytask ] & ] ;