%{
#include <stdio.h>

int ctr = 0;
%}

%union{
  int ival;
}

%token ID RP
%token <ival> LP 
%%
str	:	LP 
		{$1 = ctr++; printf("starting level %d\n",$1);}
		str_body RP
		{printf("ending level %d\n",$1);}
	;

str_body:	ID str_body	
	|	LP 
		{$1 = ctr++; printf("starting level %d\n",$1);}
		str_body RP 
		{printf("ending level %d\n",$1);}
		str_body
	|	
	;

%%

main() {
   printf("Input a balanced parenthesis/ID string:  \n");
   printf("   (example:   ( a b (c ) (d e)) \n");

  yyparse();
}