[antlr-interest] SQL grammar, keywords that can be identifiers

[Ruslan Zasukhin]

On 7/23/04 12:23 PM, "Pete Forman" <pete.forman at westerngeco.com> wrote:

> At 2004-07-22 22:33 +0300, Ruslan Zasukhin wrote:
>> join_type
>>     :    ("left" | "right" | "full" ) ( "outer"! )?
>> 
>> 
>> But SQL grammar still must accept the next query
>> 
>>     WHERE left(fld,5) = "Peter"
>>           ^^^^^
> 
> So the problem is that a token may be a keyword or not depending on the
> context.
> 
> This might be soluble in the lexer using either lexer states or lexer
> switching.  However that is moving rather a lot of the logic from the parser
> to the lexer and does not look to be a promising approach.
> 
Exactly.

> I would have the lexer aggressively return tokens whenever a keyword might be
> valid. 
> 
> The parser would then accept keywords in places where identifiers are expected
> and call setType to make them into identifiers.

> join_type
>  : (LEFT | RIGHT | FULL) (OUTER!)?;
> 
> where_clause
>  : WHERE identifier LPAREN ...
> 
> identifier
>  : IDENTIFIER
>  | (LEFT | RIGHT | FULL | OUTER) {##.setType(IDENTIFIER);};
> 
> My syntax is not checked but hopefully you'll get the idea.

So lexer returns ID,

But we add one more rule to Parser

  identifier : ..............

Which try do something more smart...

Okay we will try to think in this direction.

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
-------------------------------------------------------------
e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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