Bradford, Take a look at the tests that I wrote for that syntax, I think they will be helpful in understand what that syntax actually is: https://github.com/tc39/test262/blob/master/test/language/expressions/exponentiation/exp-operator-precedence-unary-expression-semantics.js#L34-L66
Rick On Wed, Jul 20, 2016 at 4:41 PM Bradford Smith <[email protected]> wrote: > Thanks! > I'll know to look there in future. rwalden takes good notes. > > No luck finding an answer to my question #2 though. > Searches tried: > ++ > increment > decrement > unary > UpdateExpression > > On Wed, Jul 20, 2016 at 1:22 PM Jordan Harband <[email protected]> wrote: > >> https://github.com/rwaldron/tc39-notes/search?utf8=✓&q=exponentiation >> leads me to >> https://github.com/rwaldron/tc39-notes/blob/924122cdc03e9ee2afbe8014193f845bddc6da2d/es7/2015-09/sept-23.md#exponentiation-operator >> which is when that decision was made, iirc. >> >> On Wed, Jul 20, 2016 at 1:04 PM, Bradford Smith < >> [email protected]> wrote: >> >>> Thanks for the quick response, Jordan. That does make sense for my >>> question #1. >>> >>> Re #2, does anybody know why UpdateExpression loops back up to >>> UnaryExpression? >>> >>> Also, are the reasons for the decisions made when updating the spec >>> documented anywhere? >>> If so, maybe I could find the answer to questions like these myself in >>> future. >>> >>> Thanks, >>> Bradford >>> >>> On Wed, Jul 20, 2016 at 12:55 PM Jordan Harband <[email protected]> >>> wrote: >>> >>>> `-x ** y` is absolutely a SyntaxError because of the disagreement >>>> between many programming languages which treat that as `(-x) ** y` and math >>>> itself which treats it as `-(x ** y)`. >>>> >>>> To resolve the debate about "what will users expect", this early syntax >>>> error ensures that programmers get the joy of being required to be explicit >>>> about their precedence, saving countless amounts of time and money spent on >>>> linting rules and style arguments. >>>> >>>> On Wed, Jul 20, 2016 at 12:48 PM, Bradford Smith < >>>> [email protected]> wrote: >>>> >>>>> Can anyone explain the reasoning behind the strange "leapfrogging" >>>>> behavior of the ExponentiationExpression >>>>> <https://tc39.github.io/ecma262/#prod-ExponentiationExpression> and >>>>> UpdateExpression >>>>> <https://tc39.github.io/ecma262/#prod-UpdateExpression> productions >>>>> in the current spec? >>>>> >>>>> Simplified relevant productions in operator precedence order are: >>>>> >>>>> ExponentiationExpression : >>>>> UnaryExpression >>>>> UpdateExpression ** ExponentiationExpression >>>>> >>>>> UnaryExpression : >>>>> UpdateExpression >>>>> { delete | void | typeof | + | - | ~ | ! } UnaryExpression >>>>> >>>>> UpdateExpression: >>>>> { ++ | -- } UnaryExpression >>>>> LeftHandSideExpression { ++ | -- } >>>>> >>>>> Things that seem weird about this are: >>>>> 1. '-x ** y' is a syntax error, because UnaryExpression isn't allowed >>>>> before ** >>>>> You must write it as '(-x) ** y' >>>>> I would expect the production right hand side to be >>>>> UnaryExpression ** ExponentiationExpression >>>>> That avoids this strange syntax error and is consistent with the >>>>> pattern followed by productions for lower-precedence operators. >>>>> >>>>> 2. Having UnaryExpression in the right hand side of UpdateExpression >>>>> confuses precedence by going 'backward' to a lower-precedence >>>>> non-terminal, >>>>> and the only production of UnaryExpression that generates a valid >>>>> argument for '++'/'--' is UnaryExpression => UpdateExpression => >>>>> LeftHandSideExpression anyway. >>>>> >>>>> I've just finished implementing these rules in the closure-compiler, >>>>> where I had to implement logic to deal with this strange behavior. Is it >>>>> at >>>>> all possible that these are simply typos in the spec? >>>>> >>>>> Thanks, >>>>> Bradford >>>>> >>>>> _______________________________________________ >>>>> es-discuss mailing list >>>>> [email protected] >>>>> https://mail.mozilla.org/listinfo/es-discuss >>>>> >>>>> >>>> >> _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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