Waldemar Horwat wrote:
On 09/18/2012 09:47 AM, Brendan Eich wrote:
2. Tim Disney with help from Paul Stansifer (Mozilla grad student
interns) have figured out how to implement a Reader (Scheme sense)
for JS, which does not fully parse JS but nevertheless correctly
disambiguates /-as-division-operator from /-as-regexp-delimiter. See
https://github.com/mozilla/sweet.js
This Reader handles bracketed forms: () {} [] and /re/. Presumably it
could handle quasis too. Since these bracketed forms can nest, the
Reader is a PDA and so more powerful than the Lexer (a DFA or
equivalent), but it is much simpler than a full JS parser -- and you
need a Reader for macros.
That's not possible. See, for example, the case I showed during the
meeting:
boom = yield/area/
height;
Is /area/ a regexp or two divisions and a variable? You can't tell if
you're using a purported universal parser based on ES5.1 and are
unaware that yield is a contextual keyword which will be introduced
into the language in ES6. And yes, you can then get arbitrarily out
of sync:
boom = yield/a+"3/ string?" ...
As I said to you at the meeting, there may be no problem if we simply
stop adding contextual keywords and add macros instead.
We already gave up on adding /re/x and good riddance. Getting macros
while freezing special form syntax strikes me as possibly a very good
trade-off. What do you think?
/be
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
