On Apr 24, 2010, at 22:58:35, Ron Burk wrote:
> I'm wondering if you meant to disallow spaces in your
> "interval"s. If not, then if you allow (as it appears you intend):
>
> + 15/ 7
>
> Should that "7" be interpreted as the hours part of the
> interval that starts with "15/" (meaning there's an error
> because the user forgot to supply a second interval operand
> to the '+') or should the "7" be interpreted as a second
> interval (7 seconds)?
>
> The grammar appears to be ambiguous.
Thanks for the response, and you bring up another question I had: how do I
disallow spaces in certain places?
In fact, I do wish to allow whitespace around the slash, but not around the
colons. This is because sometimes the expression is copied from a source that
puts a space between the slash and the leading hour.
My grammar rewrites something of the form a/b:c:d to (/ a b c d). This much
appears to be working fine (output from my test rig):
> 15/ + 1/ + 3.1
The tree:
(+ (+ (/ 15) (/ 1)) 3.1)
But this illustrates the problem, I think. The second sum has three children,
an interval, and two INTs, which should form an intRTL.
> 1/ 2:3:4.5 + 6:7 + 8.9
The tree:
(+ (+ (/ 1 2 3 4.5) 6 7) 8.9)
You can see the rewrite rules on line 60-61:
http://pastie.org/private/k9holwmls7emhfpgzo1oxw
I wanted to rewrite the rule on line 62 to insert a token to give the tree
walker a clue as to what was coming next, but I don't know how to insert a fake
token (or even if it's possible).
BTW, the error points to one line, but ANTLRWorks colors the intRTL rule red
when I add that sum rule on line 15. Is that a clue?
--
Rick
List: http://www.antlr.org/mailman/listinfo/antlr-interest
Unsubscribe:
http://www.antlr.org/mailman/options/antlr-interest/your-email-address
--
You received this message because you are subscribed to the Google Groups
"il-antlr-interest" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/il-antlr-interest?hl=en.
