/* Simple arith. expr. grammar (single-digit #s) with ambiguous  * grammar using assoc/prec info.  */%{#include <stdio.h>void yyerror(const char *);int yylex(void);typedef int YYSTYPE;%}%left '+' '-'%left '*' '/'%right UMINUS UPLUS%%S	  : S E { printf("%d\n", $2); } '\n'  | error '\n'  | /* empty */        ;E	  : E '+' E { $$= $1 + $3; }  | E '-' E { $$= $1 - $3; }  | E '*' E { $$= $1 * $3; }  | E '/' E { $$= $1 / $3; }  | '+' E %prec UPLUS { $$= $2; }  | '-' E %prec UMINUS { $$= -$2; }  | '(' E ')' { $$= $2; }  | '0' { $$= 0; }  | '1' { $$= 1; }  | '2' { $$= 2; }  | '3' { $$= 3; }  | '4' { $$= 4; }  | '5' { $$= 5; }  | '6' { $$= 6; }  | '7' { $$= 7; }  | '8' { $$= 8; }  | '9' { $$= 9; }  ;%%#include <stdio.h>void yyerror(const char *s) {  printf("%s\n", s);}int yylex(void) {  int c;   do { c= getchar(); } while (c == ' ' || c == '\t');  if (c == EOF) c= 0;  return c;}int main() {  return yyparse();}