Re: valid lookahead

[Akim Demaille]

>>>>> "Nils" == Nils Hasler <address@hidden> writes:

Nils> hi.  I would like to be able to figure out which terminals are
Nils> valid in any state of my parsing - just like y.output tells me.

Nils> So where in those tables can I find valid terminals following my
Nils> current state.

Have a look at out bison prepare the error message in the
YYERRROR_VERBOSE case (in the parsers).  Steal the code from there:


/*------------------------------------.
| yyerrlab -- here on detecting error |
`------------------------------------*/
yyerrlab:
  /* If not already recovering from an error, report this error.  */
  if (!yyerrstatus)
    {
      ++yynerrs;

#ifdef YYERROR_VERBOSE
      yyn = yypact[yystate];

      if (yyn > YYFLAG && yyn < YYLAST)
        {
          YYSIZE_T yysize = 0;
          char *yymsg;
          int yyx, yycount;

          yycount = 0;
          /* Start YYX at -YYN if negative to avoid negative indexes in
             YYCHECK.  */
          for (yyx = yyn < 0 ? -yyn : 0;
               yyx < (int) (sizeof (yytname) / sizeof (char *)); yyx++)
            if (yycheck[yyx + yyn] == yyx)
              yysize += yystrlen (yytname[yyx]) + 15, yycount++;
          yysize += yystrlen ("parse error, unexpected ") + 1;
          yysize += yystrlen (yytname[YYTRANSLATE (yychar)]);
          yymsg = (char *) YYSTACK_ALLOC (yysize);
          if (yymsg != 0)
            {
              char *yyp = yystpcpy (yymsg, "parse error, unexpected ");
              yyp = yystpcpy (yyp, yytname[YYTRANSLATE (yychar)]);

              if (yycount < 5)
                {
                  yycount = 0;
                  for (yyx = yyn < 0 ? -yyn : 0;
                       yyx < (int) (sizeof (yytname) / sizeof (char *));
                       yyx++)
                    if (yycheck[yyx + yyn] == yyx)
                      {
                        const char *yyq = ! yycount ? ", expecting " : " or ";
                        yyp = yystpcpy (yyp, yyq);
                        yyp = yystpcpy (yyp, yytname[yyx]);
                        yycount++;
                      }
                }
              yyerror (yymsg);
              YYSTACK_FREE (yymsg);
            }
          else
            yyerror ("parse error; also virtual memory exhausted");
        }
      else
#endif /* defined (YYERROR_VERBOSE) */
        yyerror ("parse error");
    }
  goto yyerrlab1;