Message-Passing Exercise

Lecture Notes for CS 190
Winter 2021
John Ousterhout

• Proposal:
  • Traditional procedural APIs are rigid and slow down development.
  • Better instead to use a message-passing approach.
  • Example: simple game program. Moves "sprites" in one dimension, checks for collisions.
    • game1.cc: initial implementation using traditional OOP.
    • game2.cc: reimplemented using messages.
    • game1a.cc: game1.cc restructured to hold all sprites in a single object.
    • game2a.cc: game2.cc restructured to hold all sprites in a single object.
• Claims:
  • The message passing version has no APIs or dependencies
  • Easier to make changes with the message passing approach; e.g., Game class didn't change at all in game2a.cc
  • Shouldn't define APIs before you know how you're going to use them
  • The message-based approach works even better with larger systems