llvm dev - Aug 2020 - Suggestion for TableGen ranges

The is a syntax quirk in TableGen. A leading plus or minus sign on a decimal
integer is considered part of the integer token. Coupled with this, the hyphen
(-) is used to indicate integer ranges, as in '1-5'. But the compiler
lexes '1-5' as '1' followed by '-5', so a special rule
is required to treat that as a range. It is documented as follows:

"The peculiar last form of RangePiece is due to the fact that the
"-" is included in the TokInteger, hence 1-5 gets lexed as two
consecutive TokInteger�s, with values 1 and -5, instead of "1",
"-", and "5"."

I propose that we add '..' as a new punctuation token and use it to
indicate ranges: 1..5, -10..-5. Then we can deprecate the hyphen range
construct.

On Thu, Jul 30, 2020 at 7:04 PM Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> The is a syntax quirk in TableGen. A leading plus or minus sign on a
decimal integer is considered part of the integer token. Coupled with this, the
hyphen (-) is used to indicate integer ranges, as in '1-5'. But the
compiler lexes '1-5' as '1' followed by '-5', so a
special rule is required to treat that as a range. It is documented as follows:
>
> "The peculiar last form of RangePiece is due to the fact that the
"-" is included in the TokInteger, hence 1-5 gets lexed as two
consecutive TokInteger’s, with values 1 and -5, instead of "1",
"-", and "5"."
>
> I propose that we add '..' as a new punctuation token and use it to
indicate ranges: 1..5, -10..-5. Then we can deprecate the hyphen range
construct.
I like this proposal. Feel free to ping me if you need a review.

Cheers,
Nicolai

>
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-- 
Lerne, wie die Welt wirklich ist,
aber vergiss niemals, wie sie sein sollte.

What is the protocol for deciding when a suggestion should actually be
implemented?

At 8/4/2020 04:56 PM, Nicolai Hähnle wrote:
>On Thu, Jul 30, 2020 at 7:04 PM Paul C. Anagnostopoulos via llvm-dev
><llvm-dev at lists.llvm.org> wrote:
>> The is a syntax quirk in TableGen. A leading plus or minus sign on a
decimal integer is considered part of the integer token. Coupled with this, the
hyphen (-) is used to indicate integer ranges, as in '1-5'. But the
compiler lexes '1-5' as '1' followed by '-5', so a
special rule is required to treat that as a range. It is documented as follows:
>>
>> "The peculiar last form of RangePiece is due to the fact that the
"-" is included in the TokInteger, hence 1-5 gets lexed as two
consecutive TokInteger’s, with values 1 and -5, instead of "1",
"-", and "5"."
>>
>> I propose that we add '..' as a new punctuation token and use
it to indicate ranges: 1..5, -10..-5. Then we can deprecate the hyphen range
construct.
>
>I like this proposal. Feel free to ping me if you need a review.
>
>Cheers,
>Nicolai