/**
 * JavaCC file
 */
 
options {
  JDK_VERSION = "1.5";
}
PARSER_BEGIN(eg1)
package org.simtk.parser;

public class eg1 {
  public static void main(String args[]) throws ParseException {
    eg1 parser = new eg1(System.in);
    while (true) {
      System.out.println("Reading from standard input...");
      System.out.print("Enter an expression like \"1+(2+3)*4;\" :");
      try {
        switch (eg1.one_line()) {
        case 0:
          System.out.println("OK.");
          break;
        case 1:
          System.out.println("Goodbye.");
          break;
        default:
          break;
        }
      } catch (Exception e) {
        System.out.println("NOK.");
        System.out.println(e.getMessage());
        eg1.ReInit(System.in);
      } catch (Error e) {
        System.out.println("Oops.");
        System.out.println(e.getMessage());
        break;
      }
    }
  }
}
PARSER_END(eg1)

SKIP :
{
 	" "
|	"\r"
|	"\t"
|	"\n"
}
TOKEN : /* OPERATORS */
{
	< PLUS: "+" >
|	< MINUS: "-" >
|	< MULTIPLY: "*" >
|	< DIVIDE: "/" >
}
TOKEN :
{
    < CONSTANT: ( <DIGIT> )+ >
|   < #DIGIT: ["0" - "9"] >
}
int one_line() : {}
{
  sum() ";" { return 0; }
| ";"	    { return 1; }
}
void sum() : {}
{
  term() (( <PLUS> | <MINUS> ) term())*
}
void term() : {}
{
  unary() (( <MULTIPLY> | <DIVIDE> ) unary())*
}
void unary() : {}
{
  <MINUS> element()
 | element()
}
void element() : {}
{
  <CONSTANT>
| "(" sum() ")"
}