On Fri, Jul 19, 2013 at 3:21 PM, Tab Atkins Jr. <[email protected]>wrote:
> On Fri, Jul 19, 2013 at 1:21 PM, Rick Waldron <[email protected]> > wrote: > > On Fri, Jul 19, 2013 at 1:35 PM, Tab Atkins Jr. <[email protected]> > > wrote: > >> > >> On Thu, Jul 18, 2013 at 4:34 PM, Andy Earnshaw <[email protected]> > >> wrote: > >> > It's potentially a breaking change, because > >> > > >> > 0 < 1 < 1 > >> > > >> > evaluates to false in current implementations because > >> > > >> > (0 < 1) < 1 > >> > >> Luckily, this is false in the chained operations too, since "(0 < 1) > >> && (1 < 1)" evaluates to false. > >> > >> One problem is that in current Javascript, the equality and the > >> comparison operators are at different precedence levels. Python puts > >> them at the same level, so that chaining can be purely left-to-right. > >> There's a decent chance that code does indeed depend on this, due to > >> testing equality of a comparison with a bool (which is stupid, but > >> people do it). > > > > While this is all true, the simple answer is: > > > > var a = 1, b = 2, c = 3; > > a < b < c; // true > > > > is already valid JavaScript and can't be co-opted to express new runtime > > evaluation semantics. > > Well, that's a bad example, because it's true with chained operators > too. Let c = 1.5, though, and you get different behavior. > > This type of code is broken in the first place, though. Are we > assuming that it's prevalent enough to cause problems? > It doesn't matter if you think my example is a "bad example", it's a valid expression per the language's existing grammar. Rick
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