On May 1, 2014, at 17:30, Jeffrey Kegler <[email protected]>
wrote:
> If you use them inconsistently, it can't do this and complains. One of its
> messages of complaint is the one you got.
In essence this is an ambiguous or possibly even impossible parse, right?
> On 05/01/2014 02:43 PM, Michael Roberts wrote:
>> line ::= name_group sep parmgroup sep sigil sep comment
>> name_group ::= tag | tag whitespace names
>>
>> sep ::= whitespace
>> sep ::=
>> whitespace ~ [\s]+
>>
>> sigil ::= ':' | '::' | ':*' | '{' | '[' | '<' | '('
>> | sigil template_spec
>> sigil ::=
Question to how others handle things like sep and sigil above. Since they
appear nullable is one not actually trying to say in essence that it's optional?
I usually do something like make this (some chars ommited):
line ::= stuff sep_opt sigil_opt stuff
sep_opt ::= sep*
sep ::= sepword
sigil_opt ::= sigil*
sigil ::= sigilword
sepword ~ whitespace
sigilword ~ ':'
As a way of expressing 0 or 1 of sep or sigil to indicate it's optional. Am I
making life hard for myself and should instead be using nullable alternatives?
Related to this, this is definitely one area where it seems like life would be
easier if the scanless interface supported sep? and sigil? or even just
straight quantified rules since it's capable of internally synthesizing rules
like the above and one cannot use sep* and sigil* unless they're the only
quantified rhs rule. The latter is almost always able to be "wrapped" and if
scanless could do it automatically it would speed up writing grammars. Thoughts?
-cl
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