On Sep 25, 2012, at 1:30 PM, Brendan Eich wrote: > Allen Wirfs-Brock wrote: >> I think we should go the all AssignmentExpression route. It avoid >> ArrayLiteral-like comma confusion in all three positions. It is also a >> simpler set of rules to teach and remember. > > It's different from the statement forms, though.
The statement form of if is already different in that parens are required. If you have the AssignmentExpression restriction on the paren-feree comprehension if clause a parenthesized comma expression would still be valid and look exactly like the statement form. > > Again, this is a non-issue in practice. Nobody writes comma expressions in > those places. > >> Finally, it leave open the future possibility of ArrayLiterals that have >> comprehensions in element positions. (not that I'm recommending this...) > > Why wouldn't comprehensions be allowed in ArrayLiteral element positions? > That falls out of any grammar that puts comprehensions at PrimaryExpression > precedence, where they must be. Just to be clear about what I meant... I can imagine in the future somebody proposing an extension to ArrayLiteral that would permit something like: let a = [0, n for n in range(1,10) if !(n%2), 100]; which produced similar array to [0,1,3,5,7,9,2,4,6,8,10,100]. If ES6 permits Expression in if clauses this would be incompatible change. Like you say, it's not a big deal and not necessarily an extension that I would be a fan of. > > This is not a huge deal and I defer to Jason as champion-apparent, but it > does seem worth agreeing on the same Expression non-terminal for if and for > conditions in both statements and comprehensions, or finding a better reason > to change in the latter. > > /be > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
