PARSER_BEGIN(Q3)

public class Q3 {

    public static void main(String args[]) throws ParseException {
	Q3 parser = new Q3(System.in);
	try {
	  String c_prog = parser.prog();
	  if (c_prog != null)
	    System.out.println(c_prog);
	} catch (ParseException x) {
	  System.out.println("Exiting.");
	  throw x;
	}
    }

}

PARSER_END(Q3)

/*** Ignoring whitespace ***/
SKIP :
{
    " "
  | "\n"
  | "\r"
  | "\f"
  | "\t"
}

/******************/
/***** TOKENS *****/
/******************/

TOKEN :  /* Keywords  NB - this must be placed before defn of identifiers */
{
  < CASE : "case" >
| < OF : "of" >
| < END : "end" >
| < ASSIGN : ":=" >
}

TOKEN :  
{
  < IDENT : (<LETTER>)+ >
| < #LETTER : ["a" - "z", "A" - "Z"] >
}

TOKEN : /* Punctuation */
{
  < SEMI : ";" >
| < COLON : ":" >
}


/*************************/
/***** GRAMMAR RULES *****/
/*************************/


/***** Program *****/
String prog() : 
{ String ans=null; }
{
  ans=stat() <EOF>
  { return ans; }
}


/***** Statements *****/
String stat() :
{ 
  String expression=null, caselist=null;
  Token id;
}
{
  <CASE> expression=expr() <OF> caselist=caselist() <END>
  { return "switch (" + expression + ") { " + caselist + "}"; }
| id=<IDENT> <ASSIGN> expression=expr() 
  { return id.image + " = " + expression + ";"; }
}


/***** Sequence of statements *****/
String caselist() :
{
  String cas=null, rest=null;
}
{
  cas=cas() [ <SEMI> rest=caselist() ]
  { if (rest==null) return cas; else return cas + rest; }
}

String cas() :
{
   Token id;
   String stat;
}
{
   id=<IDENT> <COLON> stat=stat()
   { return "case " + id.image + " : " + stat + " break; "; }
}

String expr() :
{}
{
   <IDENT> { return new String(token.image); }
}