Groups in Grammars

[ba01m]

When there is a group in your grammar, something like

single_match_definition      = match_field ('AS' match_field_in_event)?;

why does the sppt contain a group which contains another group. (aka why are there 2 group elements not only one?)

sppt.toStringIntended(" ") yields this:

  single_match_definition {
    match_field {
      NAME : 'field'
      WHITESPACE { "\s+" : ' ' }
    }
    §single_match_definition§multi0 { §single_match_definition§group0 { §single_match_definition§group0 {
          'AS'
          WHITESPACE { "\s+" : ' ' }
          match_field_in_event {
            NAME : 'bla'
            WHITESPACE { "\s+" : ' ' }
          }
        } } }
  }

§single_match_definition§multi0 is because of the quantifier that makes the group optional ( = ? )

I am asking because the example that is provided is too tiny (for me) to elaborate how to create my own AST objects for my grammar.

[Dr. David H. Akehurst]

hmm, that is odd.

If you rewrite the grammar making the implicit rules explicit it helps understand the SPPT:

single_match_definition = match_field ('AS' match_field_in_event)?;

becomes,

single_match_definition      = match_field optionalGroup ;
optionalGroup                     = group? ;                                      // §single_match_definition§multi0
group                                   = 'AS' match_field_in_event ;       // §single_match_definition§group0

but I believe you should not have 2 '§single_match_definition§group0' items.

Please provide me a complete grammar and example sentence that reproduces this...I will investigate.
Also, which version of AGL?

[Dr. David H. Akehurst]

I believe this should be fixed in the latest pre-release 4.0.0-rc.5
please let me know if this is now ok.

[Dr. David H. Akehurst]

I assume this is now fixed as no reply from you.
Thus I close the bug