On Wed, Feb 15, 2012 at 12:13 PM, Mark S. Miller <[email protected]> wrote:
> Many useful finite generators will not know their length ahead of time, so > this would be a poor way to detect finiteness. > Yes but you can count the times you've iterated and punt when exceeding `length`, like a poor man's stack depth hint. But yeah, pretty hacky. Infinite generators will always create many hazards of non-termination if > provided to contexts expecting finite generators. Similarly looped data > structures, if provided to contexts expecting acyclic data structures. For > the latter, at least it can be detected (as JSON.stringify does). > > While we could try to create nominal subtypes FiniteIterator and > InfiniteIterator so that iterators can declare their alleged intent, IMO > this is overengineering for a rare case. And provides no guarantees anyway. > I think we should just live with the non-termination danger. We've been > doing so for all other sources of non-termination since Turing ;). > True. But this is a little different -- syntactically, spread doesn't exactly scream "I'm calling an arbitrary, potentially non-terminating function", but neither do getters. But I'm sure we'll survive. > On Wed, Feb 15, 2012 at 7:48 AM, Dean Landolt <[email protected]>wrote: > >> >> >> On Tue, Feb 14, 2012 at 11:49 PM, Brendan Eich <[email protected]>wrote: >> >>> +1 on ... (spread) exhausting an iterator to expand the iterated values >>> into positional parameters or initialisers. >>> >> >> What about infinite generators? Punt on any iterators without a >> predefined length? Otherwise wouldn't there be some kind of exception akin >> to a stack overflow? >> > > > > -- > Cheers, > --MarkM >
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