Simple parsing problem

This should be easy practice for the experts ..
I am writing a bison grammar to parse strings coming from various
kinds of attached devices.


One of the strings is of the form:
$FOO,field1,field2, 0,a,1,b,3,c, ....<CRLF>




where there are a variable number of paired fields of the form
<number> COMMA <text> COMMA. The comma is always a delimiter here,
the text contains no commas.


This one was easy, I did it like this:
FOO opt_token opt_token dse_data_set
{mumble ...}


dse_data_set:
dse_data_pair dse_data_set
| dse_data_pair




dse_data_pair:
opt_token opt_token
{
        ...my code here ...
}
;


opt_token:
COMMA_DELIM TOKEN
{
        memcpy($$, $2, sizeof($$)/sizeof(*$$) - 1);
}
| COMMA_DELIM
{ *$$ = 0;}
;


All well and good. Now I got this curveball - it is the same as the
other one, but it has another opt_token field after the variable
length list of pairs:


$FOOBAR,field1,field2,0,a,1,b,
3,c....,field3<CRLF>


[An opt_token is just a comma delimited field that might be empty, BTW. ]


I am getting shift-reduce conflicts when I try to handle this like this:
FOOBAR opt_token opt_token dse_data_set opt_token


I can vaguely see why this is happening ... the parser can't tell the
diff between opt_tokens that are in pairs or 'in the wild'. But I am
not clear how to fix this.


I could, I suppose, define something equivalent to opt_token that does
the same thing, but is different, and use it in my dse_data_pair, or
alternatively use it for my last opt_token. But I am wondering if
there is a cleaner play.


Thanks very much


Eric

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