Re: shift/reduce conflict with unary

[cwcaceres]

Derek M Jones wrote:
> 
> cwcaceres wrote:
> 
>> Hi, I'm having shift/reduce conflict with the unary expression in my
>> grammar
>> file. I've tried using the %prec modifier but it doesn't seem to work. 
> 
> It does work, but just not in the way you wanted it to (because you have
> put it in the wrong place, but then I would probably not used it).
> 
> I take it the shift reduce conflict occurs on the input:
> 
> NUMBER PLUS NUMBER potentially-other-tokens
> 
> which can be reduced to a single summation expression
> or shifted because there may be a following UPLUS
> 
> Your problem is that you are trying to do too much in too few rules.
> 
> Create some productions for the unary operators and separate ones for
> the binary operators.  See how the C standard has done it, for an
> example.
> 
> 

Sorry, I don't understand. How would I create separate productions for unary
and binary operators?

I looked at the C++ grammar. It seems somewhat upside down, but rearranging
I think it's a bit similar to what I did which is why I'm still confused.

additive-expression:
                  multiplicative-expression
                  additive-expression + multiplicative-expression
                  additive-expression - multiplicative-expression

multiplicative-expression:
                  pm-expression
                  multiplicative-expression * pm-expression
                  multiplicative-expression / pm-expression
                  multiplicative-expression % pm-expression

pm-expression:
                  cast-expression
                  pm-expression .* cast-expression
                  pm-expression ->* cast-expression

cast-expression:
                  unary-expression
                  ( type-id ) cast-expression

unary-expression:
        unary-operator cast-expression

unary-operator: one of
                  *  &  +  -  !  ~



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