Effects

By default Crochet programs can’t do anything that users of it can observe—which mostly means they can’t do anything useful. Effects close this gap in a way that maintains Crochet’s guarantees for safety and security. And in this section we explore what exactly that means. We dive deep into what effects are, how they’re used, and how they achieve safety.

• What are effects?
  • Intentions, context, and handlers
    • Intentions
    • Contexts
    • Handlers
• Effect handlers
  • Handling an effect
  • Continuations and returns
  • Nesting handlers
  • Effect scoping
  • Missing handlers
  • Reusable handlers
    • Parameterised handlers
    • Handler initialisation
    • Default handlers
• Contextual handlers
  • Reusable handlers
  • Execution goals