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Subject: Re: question on java lang spec chapter 3.3 (unicode char lexing)
From: "Aryeh M. Friedman" <Aryeh.Friedman@gmail.com>
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Xref: csiph.com comp.lang.java.programmer:20986

On Saturday, January 5, 2013 8:34:38 AM UTC-5, Aryeh M. Friedman wrote:
> On Saturday, January 5, 2013 7:58:57 AM UTC-5, Chris Uppal wrote:
>=20
> > Patricia Shanahan wrote:
>=20
> >=20
>=20
> >=20
>=20
> >=20
>=20
> > > You would at least need to detect the escapes to get a usable error
>=20
> >=20
>=20
> > > message. Once you have done that, it is so easy to replace each escap=
e
>=20
> >=20
>=20
> > > with the equivalent Unicode character that it is not worth doing
>=20
> >=20
>=20
> > > anything else.
>=20
> >=20
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> >=20
>=20
> >=20
>=20
> > I'm not so sure about that.  IIRC the rules about interpretting Unicode=
 escapes=20
>=20
> >=20
>=20
> > have some seriously wierd convolutions. Something to do with protecting=
 against=20
>=20
> >=20
>=20
> > multiply-encoded files, I think.  It badly fails the Principle of Least=
 WTF.
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> >=20
>=20
> >=20
>=20
> >=20
>=20
> > It's in the spec, but I'm too lazy to go find the exact reference :-(
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> >=20
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> >=20
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> >=20
>=20
> >     -- chruis
>=20
>=20
>=20
> agreed for example the following is just ugly but perfectly valid Java co=
de:
>=20
>=20
>=20
> Foo.java:
>=20
> \u0070\u0075\u0062\u006C\u0069\u0063\u0020\u0063\u006C\u0061\u0073\u0073\=
u0020\u0046\u006F\u006F\u000A\u007B\u000A\u0009\u0070\u0075\u0062\u006C\u00=
69\u0063\u0020\u0073\u0074\u0061\u0074\u0069\u0063\u0020\u0076\u006F\u0069\=
u0064\u0020\u006D\u0061\u0069\u006E\u0028\u0053\u0074\u0072\u0069\u006E\u00=
67\u005B\u005D\u0020\u0061\u0072\u0067\u0073\u0029\u000A\u0009\u007B\u000A\=
u0009\u0009\u0053\u0079\u0073\u0074\u0065\u006D\u002E\u006F\u0075\u0074\u00=
2E\u0070\u0072\u0069\u006E\u0074\u006C\u006E\u0028\u0022\u0068\u0065\u006C\=
u006C\u006F\u002C\u0020\u0077\u006F\u0072\u006C\u0064\u0022\u0029\u003B\u00=
0A\u0009\u007D\u000A\u007D\u000A
>=20
>=20
>=20
> % javac Foo.java
>=20
> % java Foo
>=20
> hello, world

Just a quick note I did end up implementing unicode escapes the way JLSv3 s=
ays to and the above is one our test inputs...