[antlr-interest] proposal: make .* and .+ always nongreedy

[Terence Parr]

Hi. I'd rather not introduce new syntax.

greedy works for ('else' statement)? type rules too.

I think we should default to greedy everywhere except with .* and .+  
as they never make sense to be greedy.

Ter

On Mar 22, 2009, at 8:51 AM, George S. Cowan wrote:

> Certainly make '.*' and '.+' consistent across all the grammar  
> types, one
> way or the other.
>
> The real issue with '.*' and '.+' is of course trading off the  
> increase of
> confusion that beginning ANTLR users already have over the whole  
> issue of
> greedy/nongreedy with the need for expert users to specify grammar  
> rules
> concisely.
>
> The problems with this tiny piece of the language, the fact that you  
> raised
> the issue rather than just doing it, and the fact that several  
> people have
> taken the time to bother about replying to your note, leads me to  
> think that
> the whole greedy/nongreedy distinction is important, and it  
> therefore needs
> to be raised to a higher level and not buried in the options. Also  
> note that
> it is an option that applies only to iterative subrules and  
> therefore is an
> integral part of iteration. My limited experience with ANTLR does  
> not give
> me any special authority to make the following recommendation, so  
> take it as
> a strong statement made to clearly raise the issue for your  
> consideration:
>
> Every time we look at an iterative subrule, we need to be reminded  
> whether
> it is greedy or nongreedy; that is, we need separate operators for  
> greedy
> vs. nongreedy iteration.
>
> I suggest deprecating the current notation and using:
>  (...)** and (...)++ for greedy
>  (...)|* and (...)|+ for nongreedy
>    (or some other notation that indicates "stop me, quick")
>
> I know this is a change to the whole tradition of EBNF and regular
> expressions, so your thoughts, flames, and groans will all be  
> appreciated.
>
> George
>
>
>> -----Original Message-----
>> From: Terence Parr
>> Sent: Saturday, March 21, 2009 2:57 PM
>> To: ANTLR Interest Mailing List
>> Subject: [antlr-interest] proposal: make .* and .+ always nongreedy
>>
>>
>> http://www.antlr.org/jira/browse/ANTLR-392
>>
>> any objections?
>>
>> Ter
>>
>>
>>
>>
>