David-Sarah Hopwood wrote: > Jon Zeppieri wrote: >> On Sat, Dec 6, 2008 at 11:49 AM, Maciej Stachowiak <[EMAIL PROTECTED]> wrote: >>> On Dec 5, 2008, at 11:12 PM, Jon Zeppieri wrote: >>> >>>> I don't get it. What issue is raised by return-to-label that isn't >>>> already raised by exceptions? [...] >> Also, what was the performance issue? > > The (minor) performance issue is that if there is a lambda that returns > from a given function, all calls within that function body must check > for an escape, even if the lambda is never passed to them or otherwise > accessible to them. Similarly for calls within the scope of a labelled > statement or iteration that contains a lambda with a corresponding > 'break' or 'continue'.
Please disregard this -- I had overlooked a way to make the performance of escape continuations identical to that of exceptions. No explicit per-call checks are needed; the jump to the break/continue/return target can be handled using the same mechanism as try/catch handlers, with the same possible optimizations. In the case where the control abstraction is built-in or its implementation is inlined, the performance can be the same as conventional break/continue/return. -- David-Sarah Hopwood _______________________________________________ Es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
