[antlr-interest] syntax predicate strange behavior
Gavin Lambert
antlr at mirality.co.nz
Tue May 1 01:22:13 PDT 2007
At 19:53 1/05/2007, David Holroyd wrote:
>> By the way, this works fine:
>>
>> command_user_body
>> options {backtrack=true;}:
>> LCURL command_arguments? RCURL -> ^(USER_COMMAND
>command_arguments?) |
>> -> USER_COMMAND
>> ;
>
>With backtracking (which I admit I don't wholly understand yet)
I
>guess if it fails on the first alt, it will back-off to the
second,
>empty alternative?
Speaking of which, since (I think) USER_COMMAND and
^(USER_COMMAND) are equivalent, wouldn't the above be identical to
this (ignoring the backtracking for the moment):
command_user_body:
(LCURL command_arguments? RCURL)? -> ^(USER_COMMAND
command_arguments?);
(I could be wrong.)
More information about the antlr-interest
mailing list