/*
  adder.jj
  Simple interpreter of mathematical expression.
  By Pat Troy, February 2007
*/

options {
  STATIC = false;
  IGNORE_CASE = true;
}

PARSER_BEGIN(Adder)

public class Adder {

  public static void main(String args[]) 
    throws ParseException, TokenMgrError {
    Adder interpreter = new Adder(System.in);

    System.out.println("Welcome to the Natural Language Calculator!");
    System.out.println("I'm waiting for commands. Type 'quit' or 'exit' to quit.");

    double result = interpreter.Start();
    System.out.println ("Start returns: " + result);
   
  }

}

PARSER_END(Adder)

SKIP :
{
  " "
| "\t"
| "\r"
}


TOKEN :
{
  <NUMBER:   (["0"-"9"])+ 
           | (["0"-"9"])+ "." (["0"-"9"])+
           | (["0"-"9"])+ "."
           | "." (["0"-"9"])+ >
}
TOKEN : { < EOL : "\n"  > }
TOKEN : { < PLUS : "+" > }

double Start() throws NumberFormatException :
{
    double val;
}
{
 (
   val = Expression ()
   <EOL>
   { System.out.println ("The result is: " + val); }
 )*
 <EOF>
 {return -5.5; }
}

double Expression() throws NumberFormatException :
{
   Token t;
   double i;
   double value;
}
{
 t = <NUMBER>
 {i = Double.parseDouble (t.image); }
 {value = i;}
 (
  <PLUS>
  t = <NUMBER>
  {i = Double.parseDouble (t.image); }
  {value += i;}
 )*

  { return value; }
}