What is the problem in this yacc grammar? - yacc

Question

I have a yacc parser in which commands like "abc=123" (VAR=VAR),
abc=[1 2 3] (VAR=value_series/string) and abc=[[123]] can be parsed.
I need to parse abc=[xyz=[1 2 3] jkl=[3 4 5]].This grammar is failing due to ambiguity between rule 2 (I guess, it couldn't differentiate between value_series and the new rule.
I have tried a case:
VAR_NAME EQUAL quote_or_brace model EQUAL quote_or_brace value_series quote_or_brace net EQUAL quote_or_brace value_series quote_or_brace quote_or_brace
It didn't work.
series:
| PLUS series
{
}
| series VAR_NAME EQUAL VAR_NAME
{
delete [] $2;
delete [] $4;
}
| series VAR_NAME EQUAL quote_or_brace value_series quote_or_brace
{
delete [] $2;
}
| series VAR_NAME EQUAL quote_or_brace quote_or_brace value_series quote_or_brace quote_or_brace
{
delete [] $2;
}
| error
{
setErrorMsg(string("error"));
YYABORT;
};

Answer 1

If it was me, I would probably write a set of rules similar to this:
assignment_list
: assignment
| assignment assignment_list
;
assignment
: VAR_NAME '=' assignment_rhs
;
assignment_rhs
: expression
| '[' opt_expression_list ']' /* allows var1 = [ ... ] */
;
opt_expression_list
: /* empty */
| expression_list
;
expression_list
: expression
| expression expression_list
;
expression
: VAR_NAME /* a variable name, as in var1 = var2 */
| NUMBER /* some kind of number, as in var1 = 123 */
| STRING /* quoted string, as in var1 = "foo" */
| assignment /* allows nesting of assignments, as in var1 = [var2 = 4] */
/* also allows things like var1 = var2 = 123 */
;
Note that this isn't tested in anyway, and that I'm not fully sure about the recursion from expression to assigment.