Re: Parsing a language with optional spaces

On 7/26/20 10:56, Akim Demaille wrote:
> The most frequent cited good reasons to write parsers by hand is:
> 
> 3. tailored error messages
>    Instead of some dummy "unexpected foo, expected bar or baz", writing
>    something really helping.

All you have to do is write a rule for the incorrect construct and issue 
your own tailored message.  I do that all the time, e.g.,

                |  orexpression S_EOD
                   {
                      #if G
* |  orexpression S_EOD
                      piperm 1082,exit
                      #endif
                   }
                ;