[antlr-interest] Problem with generated code

[Jamie Penney]

Thanks for the replies everyone,

What I ended up doing was changing this into a number of different 
rules, rather than one rule for all keywords.
This created compilable code, but I don't know if it is correct. I kept 
the old code, so should I go back and
change this to use scopes?

Cheers,
Jamie Penney

Thomas Brandon wrote:
> On Feb 14, 2008 4:42 AM, Jim Idle <jimi at temporal-wave.com> wrote:
>   
>> The predicates can be hoisted (this is a feature), hence the identifier
>> is not available in the context that the predicate runs. You can avoid
>> this by using a scope:
>>
>> xxx[String ident]
>> scope
>> {
>>  String identifier;
>> }
>> @init
>> {
>>        $xxx::identifier = ident;
>> }
>>
>> ...
>> :
>>     
> Isn't that going to be hoisted into contexts prior to entering the
> rule and so before the @init action where identifier will have an
> incorrect value?
>
> Tom.
>   
>>
>>
>>     
>>> -----Original Message-----
>>> From: Jamie Penney [mailto:jpen054 at ec.auckland.ac.nz]
>>> Sent: Tuesday, February 12, 2008 5:10 PM
>>> To: antlr-interest at antlr.org
>>> Subject: [antlr-interest] Problem with generated code
>>>
>>> Hi All,
>>>
>>> I am having an issue that I wonder if someone could help me with. I
>>> have
>>> a rule:
>>>
>>> // For contextual keywords like get, set and yield
>>> contextual_keyword[string identifier]
>>>     :    { input.LT(1).Text == $identifier }? IDENTIFIER
>>>         -> {$identifier == "from"}? FROM[$IDENTIFIER]    // Transform
>>> all known contextual keywords into
>>>         -> {$identifier == "let"}? LET[$IDENTIFIER]        // their
>>> corresponding imaginary token
>>> ......................
>>>         -> {$identifier == "remove"}? REMOVE[$IDENTIFIER]
>>>         -> IDENTIFIER    // For unknown ones
>>>     ;
>>>
>>> That seems to first action seems to be pulled up into whatever other
>>> rules use this one in the generated code. So I end up with this sort
>>>       
>> of
>>     
>>> thing:
>>>                     int alt80 = 2;
>>>                     int LA80_0 = input.LA(1);
>>>
>>>                     if ( (LA80_0 == IDENTIFIER) )
>>>                     {
>>>                         int LA80_1 = input.LA(2);
>>>
>>>                         if ( ( input.LT(1).Text == identifier ) )
>>>                         {
>>>                             alt80 = 1;
>>>                         }
>>>
>>>
>>>                     }
>>>
>>> Which won't work because identifier hasn't been defined yet. The
>>>       
>> actual
>>     
>>> call to contextual_keyword() doesn't happen until well after this
>>> section, as it is further down the rule tree. So my question is, why
>>>       
>> is
>>     
>>> the first action in this rule being brought up, even though it has a
>>> dependency on the parameter passed to the rule? Is there a way to
>>>       
>> avoid
>>     
>>> this behaviour?
>>>
>>> Thanks,
>>> Jamie Penney
>>>
>>> --
>>> Jamie Penney
>>>
>>> http://www.jamiepenney.co.nz
>>>       
>>
>>     

-- 
Jamie Penney

http://www.jamiepenney.co.nz