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?" ...
Waldemar
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