Axel Rauschmayer wrote:
The way that `return()` is handled in generators (via try-catch) means that the clean-up action is called in both cases: generator exhaustion and generator closure. If you don’t use a generator then a clean-up action in `return()` is only called if the iterator is closed, not if it is exhausted. Obviously that is a minor technical detail and easy to fix (call the clean-up action when you return `{ done: true }`), but it’s still an inconsistency (which wouldn’t exist if `return()` was called in either case).
We want `return` (Python 2.5+ close) to be optional, though. So an iterator whether implemented by a generator function or otherwise sees no difference -- provided in the generator function implementation you do not yield in a try with a finally. Forcing return from a not-exhausted generator parked at yield other than in try-with-finally does not run any more code in the generator function's body.
If you, the implementor of an iterator, want to handle close (pre-exhaustion break from a for-of construct), implement `return`. If you as implementor choose a generator function to implement your iterator, you'll want that try-finally.
In this sense, return for generator function, while provided as a method of generator iterators, is encoded in the body of the generator function at the implementor's discretion (via try-yield-finally -- arguably one big try-finally with the guts that use yield in the try block).
HTH, /be _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
