[antlr-interest] still more => wars ;)

[Chris Black]

Terence Parr wrote:

>
> On Dec 8, 2005, at 2:45 PM, Chris Black wrote:
>
>> Terence Parr wrote:
>
>
> So, you'd vote for:
>
> (...) =>     syntactic predicate
> {...} =>    _hoisting_ disambiguating semantic predicate
> {...}? =>  gated semantic predicate
>
> Hmm...the two kinds of sem preds are pretty similar this way.  I do  
> like the => implies predicate though.  I wonder what we could do to  
> indicate gated.  Loring's original suggestion was
>
>
> which is verbose but these are not used much and it's clear what we  
> mean w/o new syntax.  We could then do
>
> (...) =>     syntactic predicate
> {...}?        _hoisting_ disambiguating semantic predicate
> ( {...}? ) =>  gated semantic predicate
>
> leaving everything the way they are now but adding the last syntax.
>
I think a good guiding principal on these sort of things is to shoot for 
as much consistency as possible. That is, if you can make "=>" always 
mean "predicate" (or at least semantic predicate), and have something 
else always mean hoisting, and yet another notation for gated, that 
would be the easiest to remember and understand in my opinion. So maybe:

(...) => syntactic predicate
{...} => semantic predicate
{...} ?=> hoisting disambiguating semantic predicate
{...} *=> gated semantic predicate
And, if they exist (I don't know what hoisting is, etc), to keep things 
consistent:
(...) ?=> hoisting disambiguation syntactic predicate
(...) *=> gated syntactic predicate

As you can see, I also prefer all the notation to be part of the "=>" 
sequence rather than split up. You'll also notice that {...} is always 
semantic and (...) always syntactic.

Chris