On Apr 2, 2008, at 1:03 PM, Lars Hansen wrote: > Looks like those restrictions (condition only at the end, only 'for', > 'for each', > and 'if' clauses) originate in Brendan's original (too-sketchy) > proposal, see > the "Comprehensions" section of this page: > > http://wiki.ecmascript.org/doku.php? > id=proposals:iterators_and_generator > s
This is my fault -- I went by the examples in http://www.python.org/dev/peps/pep-0202/ and did not include the full grammar from http://www.python.org/doc/current/ref/lists.html#l2h-238 cited therein -- apologies to all and thanks to Jason for pointing this out. > IMO we're looking for simple and useful comprehensions for ES4. I > think extensions like the ones you are suggesting, though clearly > useful, > should be prototyped elsewhere before going into the language spec, or > at a minimum, be presented in a better developed proposal. This is all thin syntactic sugar, so I don't agree it rocks the boat too much to follow the full prototype in Python. I'll update the proposal, since it claims to follow the PEP, but fails since the PEP cites the RM. Jason wrote: >> Separately, I would appreciate let clauses in ArrayComprehensions: >> >> [[trial, phi] >> for each (trial in trials) >> let (phi = hugeExpensiveCalculation(trial)) >> if (phi < 1000)] >> >> Haskell has this feature. I occasionally reach for it in >> Python and it isn't there. Lars, you didn't cite this use-case for let statements, aka let blocks :-P. Firefox 2 and 3 (JS1.7 and 1.8) have support for let blocks, but again not embedded in comprehensions. As Jason notes, Python didn't follow Haskell here (if that was the order of evolution). I don't propose we do this for ES4, since let blocks are "out" according to all who've opined on the spreadsheet. /be _______________________________________________ Es4-discuss mailing list Es4-discuss@mozilla.org https://mail.mozilla.org/listinfo/es4-discuss
