package base

A token representing state from the beginning of an iteration.

Capture state at the start of iteration.

assert_no_mutation_since_start t queue raises if any mutation has happened to queue since t was created by start queue. Results are unspecified if you call assert_no_mutation_since_start with a different queue from the one passed to start.

Call assert_no_mutation_since_start after each step of an iteration loop, before checking if the queue is empty or advancing to the next element. This ensures these read operations are consistent with the queue's state at the start of iteration.