That should throw a syntax error since it uses 'in' instead of 'of'. Other than that I'm in favor of proposal 5 (for (for | if)*).
If we go with the current ES6 draft and you used 'of' instead of 'in' it would have been a syntax error. On Mon, Sep 24, 2012 at 11:29 AM, Jason Orendorff <[email protected]> wrote: > On Sat, Sep 22, 2012 at 11:57 PM, Allen Wirfs-Brock > <[email protected]> wrote: >> actually what I meant to say was that personal preference for ES6 >> comprehensions, in increasing complexity order is: >> 1) [a non-starter alternative] >> 2) a single for clause followed by a single optional if clause >> 3) one or more for clauses followed by a single optional if clause (what >> is in the current draft) >> 4) a sequence where each element consists of a for clause and an optional >> if clause > > We disagree on what notion of complexity is important here. > > The amount of implementation complexity we're talking about here is > peanuts. I can implement all the options we've discussed by lunchtime. > It's just not an issue. I can fit all the proposals in a tweet using > a little BNF: > > 1. nothing 2. for if? 3. for+ if? 4. (for if?)* > 5. for (for|if)* 6. (for|if|let)* > > (I include your proposal 4 for completeness, but no one has really > proposed that. 5 is Python and 6 is Haskell--the two proposals I > favor.) > > But what is actually at issue here is how JS should treat the > developer who writes this: > > books = [book for author in authors > if author.home_state == 'TN' > for book in author.books()]; > > And the options here are (1) run it; (2) throw a SyntaxError. If it > throws, the developer will be surprised. They will have to rephrase > their thought to fit our syntactic whims; and they will have to add a > rule to their mental model of the language. I claim this is the > notion of complexity we should worry about. > > -j > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss -- erik _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
