Re: Add null identifiers to genmatch

[Pedro Alves]

Hi Richard,

Passerby comment below.

On 11/07/2015 01:21 PM, Richard Sandiford wrote:
> -/* Lookup the identifier ID.  */
> +/* Lookup the identifier ID.  Allow "null" if ALLOW_NULL.  */
>  
>  id_base *
> -get_operator (const char *id)
> +get_operator (const char *id, bool allow_null = false)
>  {
> +  if (allow_null && strcmp (id, "null") == 0)
> +    return null_id;
> +
>    id_base tem (id_base::CODE, id);

Boolean params are best avoided if possible, IMO.  In this case,
it seems this could instead be a new wrapper function, like:

id_base *
get_operator_allow_null (const char *id)
{
  if (strcmp (id, "null") == 0)
    return null_id;
  return get_operator (id);
}

Then callers are more obvious as you no longer have to know
what true/false mean:

       const char *id = get_ident ();
-      if (get_operator (id) != NULL)
+      if (get_operator_allow_null (id) != NULL)
        fatal_at (token, "operator already defined");


vs:

       const char *id = get_ident ();
-      if (get_operator (id) != NULL)
+      if (get_operator (id, true) != NULL)
        fatal_at (token, "operator already defined");


Thanks,
Pedro Alves