doc/calc.y

   1 %union
   2 {
   3   int ival;
   4   const char *sval;
   5 }
   6
   7 %token <ival> NUM
   8 %nterm <ival> exp
   9 %token <sval> STR
  10 %nterm <sval> useless
  11
  12 %left '+' '-'
  13 %left '*'
  14
  15 %%
  16 exp:
  17   exp '+' exp
  18 | exp '-' exp
  19 | exp '*' exp
  20 | exp '/' exp
  21 | NUM
  22 ;
  23 useless: STR;