Problem in grammar

[Godeau Julien]

Hello,

I have a problem with my grammar that I don't manage to solve and a
little help would really be greatful :o)

Here is the situation : I use Bison for a command interpreter. I deal
with variables (float values) and signals (object that contains
informations and a tab of float values that can be plotted).

Here is 2 examples of common use :

 

My_var = 3. + 1.

My_signal = 4. + My_other_signal

Mysignal = My_other_signal + 4.

 

Let's assume that My_var and My_signal are new identifiers, my problem
is that in the second example the command "Mysignal = 4." is recognized
by Bison as an integer variable assignment (with parsing error because
of "My_other_signal") while what should have been done is to recognize
that "4. + My_other_signal" is a signal (and process it) and then do a
signal assignment. In the third example, it works fine.

 

I don't manage to tell Bison that the priority is to process what is at
the right of the '=' before assigning the result using the good rule

 

*       Here are the precedence and priority used :

 

%right '='

%left OPERATOR1        /* '+' '-' */

%left OPERATOR2        /* '*' '/' */

%left '(' ')'

%left UNARY            /* for '-3' */

 

*       Here are the rules used

 

base : /* empty */

     | var_asgn                

     | signal_asgn

;

 

new_id_equal : IDENTIFIER '=' { $$ = $1; }

;

 

var_asgn : new_id_equal float_val { $$ = $2; } 

;

 

signal_asgn : new_id_equal signal { $$ = $2;}

;

 

float_value : FLOAT_VALUE                         { $$ = $1; }

            | float_value OPERATOR1 float_value   { $$ = ... }

            | float_value OPERATOR2 float_value   { $$ = ... }


            | '(' float_value ')'                 { $$ = $2; }

            | OPERATOR1 float_value %prec UNARY   { $$ = -$2; }      

;      

 

signal : '(' signal ')'                  { $$ = $2; }           

       | full_function_call              { $$ = $1; }

       | OPERATOR1 signal %prec UNARY    { $$ = ... }

       | signal OPERATOR1 signal         { $$ = ... }

       | signal OPERATOR2 signal         { $$ = ... }


       | signal OPERATOR1 float_value    { $$ = ... }        

       | float_value OPERATOR1 signal    { $$ = ... }    

       | signal OPERATOR2 float_value    { $$ = ... }               

       | float_value OPERATOR2 signal    { $$ = ... }


;

 

full_function_call : ...

;

 

Do you have any information that could help me ?

Best regards,

 

Julien