Re: FYI: default %printer/%destructor

[Hans Aberg]

On 25 Nov 2006, at 03:00, Joel E. Denny wrote:

> > You would need a rule telling, in the case of multiple  
> > occurrences, when the
> > default names can be used.
>
> I addressed the problem of ambiguous names here:
>
>   http://lists.gnu.org/archive/html/bison-patches/2006-11/ 
> msg00039.html

Here, another way analyzing what is going on.

Symuppse the grammar and action language identifiers have different  
syntax. If the former, but not the latter, accepts "-" in  
identifiers, then one could write:

  arithmetic-expression:
      INTEGRAL_NUMBER//		                             
#identity_INTEGRAL_NUMBER
    | '-' arithmetic-expression/x %prec NEGATION            #neg
    | '(' arithmetic-expression// ')'	                     
#identity_expression
    | arithmetic-expression// '+' arithmetic-expression//   #add
    | arithmetic-expression/x '-' arithmetic-expression//   #sub
    | arithmetic-expression// '*' arithmetic-expression/y   #mul
    | arithmetic-expression/x '/' arithmetic-expression//   #div
    | arithmetic-expression// '^' arithmetic-expression/y   #pow
  ;

identity_INTEGRAL_NUMBER { $$ = $INTEGRAL_NUMBER; }
neg { $$ = -$arithmetic-expression ; }
identity_expression { $$ = $arithmetic-expression; }
add { $$ = $arithmetic-expression + $y; }
sub { $$ = $x - $arithmetic-expression; }
mul { $$ = $arithmetic-expression * $y; }
div { $$ = $x / $arithmetic-expression; }
pow { $$ = pow($arithmetic-expression, $y); }

Here, it does not work in the actions, because the variable names  
contain "-". The reason is that syntax of two different languages  
(i.e., grammar and action languages) are mixed indiscriminately.

So, strictly speaking, the explicitly indicated variables should  
follow the action language syntax, though that may not be fully  
possible. One way to ensure this, though, might be to somehow admit C- 
strings as variable names. For example:
  expression:
    ...
    | expression/"#1" '+' expression/"#2"   { $#1 + $#2 }
    ...
    ;
if there is an action variable that admits "#" in the variable names.

  Hans Aberg