Rho-Calculus Counter Implementation: Increase, Reset, and Check

This code snippet showcases a counter implementation using the Rho-calculus. It demonstrates how to define channels, methods, and use channel communication to manipulate the counter value.

new currentCount, increase, reset, check, stdout('rho:io:stdout') in {
  // Starting the counter at 0
  currentCount!(0) |
  // Method to increase counter (returns the old value)
  contract increase(ack) = {
    for(old <- currentCount) {
      currentCount!(*old + 1) |
      ack!(*old)
    }
  } |
  // Method to reset the counter (returns the old value)
  contract reset(ack) = {
    for(old <- currentCount) {
      currentCount!(0) |
      ack!(*old)
    }
  } |
  // Increase the value three times
  new ack in {
    increase!(*ack) |
    for(_ <- ack) {
      increase!(*ack) |
      for(_ <- ack) {
        increase!(*ack) |
        for(_ <- ack) {
          increase!(*ack) |
          // And check it's value afterwards
          for(_ <- ack; count <- currentCount) {
            stdout!(*count)
          }
        }
      }
    }
  }
}

Explanation:

• currentCount Channel: Represents the current value of the counter, initialized to 0.
• increase Method: Takes an ack channel, reads the current value from currentCount, increments it, updates currentCount, and returns the previous value through ack.
• reset Method: Takes an ack channel, sets currentCount to 0, and returns the previous value through ack.
• Main Code: Creates a new ack channel, calls increase three times consecutively, and finally reads the final counter value from currentCount and outputs it to stdout.

This code demonstrates a basic yet effective implementation of a counter using Rho-calculus' channel communication and method definition capabilities.