So things that
are doing are:
Single binding on 'or'
$binding : ( Pattern() || Pattern() )
We are thinking of only allowing 'or' between patterns and not
allowing users to mix and match 'or' and '||'. Inside of patterns
'||' is the only connective allowed and will remain so.
OK, a clear distinction avoids confusion.
We will also probably make a choice and only allow infix 'or' and
'and', at the moment users can chose infix or prefix. Personally I
find prefix quite attractive as it works sort of like a "choice":
(or Person( ... )
Person( ... )
Person( ...) )
But I think most peopel are more comfortable with infix:
(Person( ... ) or
Person( ... ) or
Person( ...) )
(name ... ) is neither function style nor infix, so removing yet another way of writing expressions is OK. Let's infix.
return value, eval, literal constraint, variable constraint are
going. These are left overs of a Clips based grammar. So instead
we'll have a generic "expr" class that follow more common modern
ASTs for expression engines, like say MVEL.
OK!
Davide has also requested that we make $ prefix mandatory for LHS
bindings as that is deterministic and again makes the grammar
cleaner.
I don't understand why it should be "cleaner". After all, a '$' could even result from a Java identifier although this is discouraged, according to the Language Spec.
I personally like it being optional and it's still open to
debate. But I recognise the need to have better maintained grammar,
that is more consistent and regular with easy to main documentation.
There's one thing that would help: Make the NT identifiers in the grammar "user friendly". I had to replace all of them with NT identifiers that are self-explanatory. Also, whenever possible, stick to the terms in the Java grammar if it's the same thing, e.g. "QualifiedIdentifier", "Block", "Expression", etc.
-W
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