Resource Management

AIVI provides a dedicated Resource type to manage lifecycles (setup and teardown) in a declarative way. This ensures that resources like files, sockets, and database connections are always reliably released, even in the event of errors or task cancellation.

15.1 Defining Resources

Resources are defined using resource blocks. The syntax is analogous to generators: you perform setup, yield the resource, and then perform cleanup.

The code after yield is guaranteed to run when the resource goes out of scope.

// Define a reusable resource
managedFile path = resource {
  handle <- file.open path  // Acquire
  yield handle              // Provide to user
  _ <- file.close handle    // Release
}

This declarative approach hides the complexity of error handling and cancellation checks.

15.2 Using Resources

Inside an effect block, you use the <- binder to acquire a resource. This is similar to the generator binder, but instead of iterating, it scopes the resource to the current block.

main = effect {
  // Acquire resource
  f <- managedFile "data.txt"
  
  // Use resource
  content <- file.readAll f
  print content
} // f is automatically closed here

Multiple Resources

You can acquire multiple resources in sequence. They will be released in reverse order of acquisition (LIFO).

copy src dest = effect {
  input  <- managedFile src
  output <- managedFile dest
  
  _ <- file.copyTo input output
}