[antlr-interest] How to describe this in ANTLR?

[Daniel Shane]

Hi, I have two cases I'm trying to solve using ANTLR..

First, what is the best way of writting this so that its deterministic?

a: b? c? d? e? f? b?

Is this the best way?

a: (b (c | d | e | f)) => b c? d? e? f? b?
| (c | d | e | f) => c? d? e? f? b?
| b?

Secondly, I'm trying to recognize text which contain footnotes. For example:

Section
This is paragraph 1 * <- footnote Reference
This is paragraph 2 ** <- footnote Reference
** footnote 2
* footnote 1

A section can end with a footnote as well as paragraphs. If the footnote is 
for the preceding paragraph, then it goes with it, else it goes at the end 
of the section.

section: paragraph+ footnote*
paragraph: text footnoteRef? footnote*
footnote: footnoteRef text

The problem is that stated this way the grammar is non deterministic, 
however, by matching the footnoteRef to the footnote it is possible to know 
if a footnote goes in the section or at the end of a paragraph.

In the above example, here is the tree that should be recognized:

<Section>
<Paragraph><text>This is paragraph 
1</text><footnoteRef>*</footnoteRef></Paragraph>
<Paragraph><text>This is paragraph 2</text><footnoteRef>**</footnoteRef>
<footnote><footnoteRef>**</footnoteRef> footnote 2</footnote>
</Paragraph>
<footnote><footnoteRef>*</footnoteRef> footnote 1</footnote>
</Section>

Is there a way to accomplish this using semantic predicates? If I understand 
semantic predicate will return an error and parsing will fail if the 
condition evaluates to anything but true right? So I can place a semantic 
predicate that would try to match the footnote with the right footnoteRef?

Daniel Shane

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