[antlr-interest] "protected" lexer rules

Terence Parr parrt at cs.usfca.edu
Mon Nov 8 09:17:09 PST 2004



On Nov 7, 2004, at 3:47 PM, John D. Mitchell wrote:

>
>>>>>> "Terence" == Terence Parr <parrt at cs.usfca.edu> writes:
>>>>>>> On Nov 7, 2004, at 3:17 PM, John D. Mitchell wrote:
> [...]
>
>>>> "non token"?  "method"?  "macro"?  "internal"?
>
>>> Their only purpose for existence is to provide a single definition 
>>> of a
>>> (sub-)structure of (perhaps many) token(s), right?  So, they are 
>>> really
>>> just "shorthand" (rules).
>
>> Yes, common substructure with optional actions; e.g., DIGIT might 
>> compute
>> a value from the char.
>
>> So, "shared", "isolated", "common", "sub"?
>
> "Sub" rule is very bad because it's already got a meaning.

Yeah, it's an ambiguous term already, true.  "subrule" I started using 
a decade ago to mean EBNF stuff; i.e., an anonymous embedded rule.  
However, it's also convenient to use the term for a rule invoked by 
another rule.  Heh, wait, did I just convince myself that subrule is 
not a bad keyword since it's similar enough to one and identical to the 
other?  EBNF should really be embedded rule, but regardless, most 
people will get it if I say:

INT : (DIGIT)+ ;

subrule
DIGIT : '0'..'9' ;

The problem with protected (equally private) is that the intended 
meaning is a side effect of the main meaning of the word.  The above 
snippet would be clear to anybody just casually looking at a new 3.0 
grammar, right?

Hmm....

Ter

>
> "Common" and "shared" rules are both too generic in addition to the 
> fact
> that the shorthand rule isn't necessarily commonly used or shared.
>
> At this point, "shorthand" is the best that I can come up with.  That 
> name
> is clear; it's not overused in Antlr, the grammar/language community, 
> the
> or the general computing world; and it's descriptive of the rule's
> functional role.
>
>
>> perhaps there is a different "section"; one for regular rules and then
>> one for these shared rules?
>
> Naw, I prefer to have the helper rules next to the rule that they help.
>
> Hope this helps,
> 		John
>
>
>
> Yahoo! Groups Links
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--
CS Professor & Grad Director, University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
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