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Groups > comp.lang.java.programmer > #39444

Re: Character.isIdentifierIgnorable

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On 4/24/20 10:24 PM, Arne Vajhøj wrote:
> On 4/24/2020 8:37 PM, Jeff Higgins wrote:
>> On 4/24/20 8:29 PM, Arne Vajhøj wrote:
>>> I think we are in the far out corners of the language.
>>>
>> Well, yeah, but still.
>> And still leaves me questioning motivation for ignorable chars.
> 
> We would need to find someone working at SUN back in the mid 90's
> to know.
> 
> If I were to guess then somebody got the "smart" idea that
> the language should not distinguish between names where
> the difference could not be seen when type'd/cat'ed and
> then someone else later added the \uXXXX feature.
> 
Maybe not that far back.

from JLS-3.8 for JavaSE 9
Two identifiers are the same only if they are identical, that is, have 
the same
Unicode character for each letter or digit. Identifiers that have the 
same external
appearance may yet be different.

from JLS-3.8 for JavaSE 10
Two identifiers are the same only if, after ignoring characters that are
ignorable, the identifiers have the same Unicode character for each letter
or digit. An ignorable character is a character for which the method
Character.isIdentifierIgnorable(int) returns true. Identifiers that have the
same external appearance may yet be different.

from OpenJDK com/sun/tools/javac/parser/JavaTokenizer.scanIdent()

if (Character.isIdentifierIgnorable(reader.ch)) {
   reader.scanChar();
   continue;
}

So openJDK javac eliminates ignorable chars before he even attemps to 
build AST

Looking at org.eclipse.jdt.internal.compiler.parser.Scanner right now
but is a real clusterfk.

No response from Eclipse JDT forum yet.

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Thread

Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 18:46 -0400
  Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-24 18:54 -0400
    Re: Character.isIdentifierIgnorable Martin Gregorie <martin@mydomain.invalid> - 2020-04-24 23:07 +0000
    Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 20:12 -0400
      Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-24 20:29 -0400
        Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 20:37 -0400
          Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-24 22:24 -0400
            Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 23:36 -0400
              Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-25 12:57 -0400
                Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-25 13:01 -0400
                Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-25 13:39 -0400
                Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-25 13:51 -0400
                Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-25 14:36 -0400
            Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 23:41 -0400
    Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 20:25 -0400
      Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-24 20:32 -0400
        Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-24 20:42 -0400
          Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-25 09:53 -0400
            Re: Character.isIdentifierIgnorable Arne Vajhøj <arne@vajhoej.dk> - 2020-04-25 12:55 -0400
              Re: Character.isIdentifierIgnorable Jeff Higgins <invalid@invalid.org> - 2020-04-25 13:43 -0400

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